Effects of Four- Lane Highways on Desert Kit Fox and Swift Fox:
Inferences for the San Joaquin Kit Fox Population
Report number CA10- 1095
Final Report
State of California, Department of Transportation
Division of Research and Innovation, Office of Materials and Infrastructure Research
April 30, 2010
Effects of Four- Lane Highways on Desert Kit Fox and Swift Fox:
Inferences for the San Joaquin Kit Fox Population
Final Report
Prepared by
Anthony P. Clevenger1
Angela V. Kociolek1
Brian L. Cypher2
1Western Transportation Institute
College of Engineering
Montana State University
2Endangered Species Recovery Program
California State University, Stanislaus
A report prepared for the
State of California
Department of Transportation
Division of Research and Innovation
Office of Materials and Infrastructure Research
April 30, 2010
STATE OF CALIFORNIA DEPARTMENT OF TRANSPORTATION
TECHNICAL REPORT DOCUMENTATION PAGE
TR0003 ( REV. 10/ 98)
1. REPORT NUMBER
CA10- 1095
2. GOVERNMENT ASSOCIATION NUMBER
3. RECIPIENT’S CATALOG NUMBER
4. TITLE AND SUBTITLE
Effects of Four- Lane Highways on Desert Kit Fox and Swift Fox:
Inferences for the San Joaquin Kit Fox Population
5. REPORT DATE
April 30, 2010
6. PERFORMING ORGANIZATION CODE
7. AUTHOR( S)
Clevenger, A. P., A. V. Kociolek and B. L. Cypher
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
California Department of Transportation
Division of Research and Innovation, MS- 83
1227 O Street
Sacramento CA 95814
10. WORK UNIT NUMBER
11. CONTRACT OR GRANT NUMBER
65A0250
12. SPONSORING AGENCY AND ADDRESS
California Department of Transportation
Sacramento, CA 95819
13. TYPE OF REPORT AND PERIOD COVERED
Final Report;
October 2007 – January 2010
14. SPONSORING AGENCY CODE
15. SUPPLEMENTAL NOTES
Cover photo: Swift fox using a culvert to cross I- 70 in eastern Colorado. Photo taken by remote triggered infrared
camera.
16. ABSTRACT
Limited information is available on whether San Joaquin kit fox ( Vulpes macrotis mutica) use below grade
passages, design parameters that might facilitate their use, or what rate of passage is needed to offset habitat
connectivity losses. This final report details four field studies conducted between September 2007 and January
2010. Swift fox ( Vulpes velox) were studied in Colorado and South Dakota and desert kit fox ( Vulpes macrotis
arsipus) were studied in California. The aim of these companion studies was to investigate the movements and
crossing behavior of swift and desert kit foxes around four- lane highways. The four- lane highways in our study
areas were generally not a barrier to movement of swift fox and desert kit fox. Small sample sizes of fox
crossings at monitored culverts prevented the ability to determine optimal crossing structure design for San
Joaquin kit foxes. Nonetheless, some general principles with regard to design of wildlife crossings can be used
as guidelines for this species. The best practice would be to install as many culverts or crossing structures as
possible within San Joaquin kit fox range and where local habitat conditions are favorable.
17. KEY WORDS
San Joaquin Kit Fox, Vulpes macrotis mutica, Desert
Kit Fox, Vulpes macrotis arsipus, Swift Fox, Vulpes
velox, four- lane highways, crossing structures, culverts
18. DISTRIBUTION STATEMENT
No restrictions. This document is available to the
public through the National Technical Information
Service, Springfield, VA 22161
19. SECURITY CLASSIFICATION ( of this report)
Unclassified
20. NUMBER OF PAGES
66
21. PRICE
Reproduction of completed page authorized
Effects of Four- Lane Highways Executive Summary
Western Transportation Institute Page iv
EXECUTIVE SUMMARY
Highway expansion projects are being planned in San Joaquin kit fox ( Vulpes macrotis mutica)
habitat. In an effort to maintain habitat connectivity, California Department of Transportation
( Caltrans) has begun incorporating culvert- like conduits as wildlife crossing structures into these
highway projects ( Clevenger 2005). Limited information is available on whether kit fox use
below grade passages such as culverts ( Bremner- Harrison et al. 2007), design parameters that
might facilitate their use, or what rate of passage is needed to offset habitat connectivity losses
( Clevenger 2005).
This final report details four field studies conducted between September 2007 and January 2010.
Swift fox ( Vulpes velox) were studied in Colorado and South Dakota and desert kit fox ( Vulpes
macrotis arsipus) were studied in California. The aim of these companion studies was to
investigate the movements and crossing behavior of swift and desert kit foxes around four- lane
highways. We consider data collected on these surrogate species to be pertinent for making
mitigation recommendations to benefit long- term San Joaquin kit fox recovery.
The four- lane highways in our study areas were generally not a barrier to movement of swift fox
and desert kit fox. Thus, we can assert the same highway- crossing relationship is true for San
Joaquin kit fox. Mortality of foxes does occur throughout the year but rates of mortality appear
to be sustainable for local populations of foxes. Sustainable rates of mortality will likely occur in
core areas of San Joaquin kit fox range. However, in non- core or marginal areas, road- related
mortality could have serious negative consequences for local populations and pose a significant
risk to long- term persistence.
Small sample sizes of fox crossings at monitored culverts prevented the ability to determine
optimal wildlife crossing structure design for San Joaquin kit foxes. Nonetheless, some general
principles with regard to design of wildlife crossing structures can be used as guidelines for this
species ( Clevenger and Huijser 2009).
The best practice would be to install as many culverts or wildlife crossing structures as possible
within San Joaquin kit fox range and where local habitat conditions are favorable. Given the
average home range size of San Joaquin kit foxes ( 5.9 km2 with 2.7 km diameter; Nelson et al.
2007), we recommend a minimum of one culvert or crossing structure every 0.5 km ( 0.3 mi).
This would result in multiple opportunities for below grade crossings in each fox home range.
Culverts and crossing structures should be variable in size but a minimum diameter of 61 cm ( 24
in). In larger culverts, crossing structures and underpasses, escape dens should be constructed.
Solid median barriers have the potential to obstruct at- grade movement and can increase time
spent on highways and thus the risk of road- related mortality. Therefore solid median barriers
should not be constructed on highways in San Joaquin kit fox range. Alternative median barrier
designs that allow for greater cross- highway movement should be incorporated into new
highway designs. In the absence of median barriers, fencing is not necessary. When animals are
successfully crossing roads and mortality from vehicles is not a limiting factor, fencing should be
discouraged. If solid median barriers are present, then fencing may be beneficial in helping guide
foxes to below grade crossing opportunities.
Effects of Four- Lane Highways Executive Summary
Western Transportation Institute Page v
Critical to the effective planning of mitigation for San Joaquin kit foxes will be science- based
information obtained from species occurrence surveys where transportation projects may impact
local populations and their long- term persistence.
Effects of Four- Lane Highways Table of Contents
Western Transportation Institute Page vi
TABLE OF CONTENTS
1. Background .............................................................................................................................. 1
1.1. Project purpose................................................................................................................ 1
1.2. Study approach................................................................................................................ 1
2. Effects of four- lane highways on swift fox .............................................................................. 4
2.1. First field season ( October 2007 to January 2008), Colorado ........................................ 4
2.1.1. Study area................................................................................................................ 4
2.1.2. Methods................................................................................................................... 8
2.1.3. Results ..................................................................................................................... 9
2.1.4. Discussion ............................................................................................................. 18
2.2. Second field season ( May 2009 to January 2010), South Dakota ................................ 19
2.2.1. Study area.............................................................................................................. 19
2.2.2. Methods................................................................................................................. 20
2.2.3. Results ................................................................................................................... 25
2.2.4. Discussion ............................................................................................................. 32
3. Effects of four- lane highways on desert kit fox ..................................................................... 34
3.1. First field season ( October 2007 to June 2008), California .......................................... 34
3.1.1. Study area.............................................................................................................. 34
3.1.2. Methods................................................................................................................. 34
3.1.3. Results ................................................................................................................... 35
3.1.4. Discussion ............................................................................................................. 37
3.2. Second field season ( June to July 2009), California ..................................................... 38
3.2.1. Study area.............................................................................................................. 38
3.2.2. Methods................................................................................................................. 38
3.2.3. Results ................................................................................................................... 38
3.2.4. Discussion ............................................................................................................. 38
4. Conclusions ............................................................................................................................ 40
4.1. Colorado swift fox study ............................................................................................... 40
4.2. South Dakota swift fox study ........................................................................................ 40
4.3. California desert kit fox study ....................................................................................... 41
5. Recommendations .................................................................................................................. 42
5.1. Connectivity zones ........................................................................................................ 43
Effects of Four- Lane Highways Table of Contents
Western Transportation Institute Page vii
5.2. Median barriers ............................................................................................................. 46
5.3. Below and above grade passage design and planning .................................................. 46
5.4. Fencing........................................................................................................................ . 47
5.5. Prey traps ...................................................................................................................... 48
5.6. GPS technology ............................................................................................................ 48
5.7. Species occurrence surveys ........................................................................................... 48
6. References .............................................................................................................................. 50
7. Appendix A ............................................................................................................................ 53
7.1. 2009– 2010 South Dakota culvert monitoring scheme and swift fox detections .......... 53
Effects of Four- Lane Highways List of Figures
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LIST OF FIGURES
Figure 1. View of study area looking east. ..................................................................................... 4
Figure 2. Study area west of Limon, Colorado. .............................................................................. 6
Figure 3. Study area east of Limon, Colorado. ............................................................................... 7
Figure 4. Remotely triggered image taken on 15 January 2008, eight days past programmed
drop- off date. After several attempts, this fox was not recaptured. ...................................... 11
Figure 5. Remotely triggered image taken on 14 January 2008, four days past programmed drop-off
date. This female fox ( CH66) was recaptured on 18 January 2008. ............................... 11
Figure 6. Seasonal home range of an adult GPS- collared female swift fox ( CH 66) in relation to
I- 70 west near Limon, Colorado. Triangles represent GPS location fixes. This location is in
the upper left quadrant of the western study area map. ........................................................ 12
Figure 7. Number of instances of species ( or groups) detected in or near entrances of below-grade
passages in western study area. ................................................................................... 13
Figure 8. Number of instances of species ( or groups) detected in or near entrances of below-grade
passages in eastern study area. .................................................................................... 14
Figure 9. Number of instances when track bed condition precluded track detectability. There was
an instance where a culvert was not monitored because of an unsafe traffic situation. ....... 15
Figure 10. Swift fox documented inside reinforced concrete pipe culvert ( R351.2) confirms a
crossing occurred via the culvert. Snow can be seen in foreground. .................................... 16
Figure 11. Another view of the individual in Figure 10 confirms it is an unmarked fox. This
individual appears to be attracted to the seam where a rodent might live. ........................... 16
Figure 12. A second instance of a swift fox documented crossing via R351.2. ........................... 17
Figure 13. View of R351.2 entrance ( 152 cm [ 60 in]) in diameter ( left) and adjacent landscape
( right). ............................................................................................................................... ... 17
Figure 14. View of both entrances of R368.1; 52 x 104 cm ( 20.5 x 41 in; height x width) at
eastbound entrance ( left) and 93 x 118 cm ( 36.5 x 46.5 in) at westbound entrance ( right). 18
Figure 15. Study area along I- 90, east of Wall, South Dakota. .................................................... 20
Figure 16. Distribution of culverts ( black rings) and natal den locations ( red balloons). For ease
of viewing, only culvert entrances on the eastbound side of the highway (- E) are shown. B –
concrete box culvert, TB – concrete tunnel box culvert ( discovered to have high human use,
therefore, not monitored), R – reinforced concrete pipe culvert. The elliptical- shaped
reinforced concrete pipe culvert label is not shown on map. ................................................ 22
Figure 17. Fence installation ( clockwise from top left: a vehicle- mounted spool aids in laying out
~ 5.6 km ( 3.5 mi) of fencing; several inches of mesh stapled to the ground creates a barrier
to digging under the fence line; t- posts enable angling the mesh away from the right- of- way
fence line ( foreground) to the culvert entrances ( location of workers in the mid- ground). .. 24
Figure 18. Snow filled culvert entrances and negated the effectiveness of the fencing. T- posts
delineate where chicken wire fencing funneled to culvert entrances. .................................. 30
Effects of Four- Lane Highways List of Figures
Western Transportation Institute Page ix
Figure 19. Top two images feature an individual with unequal eye shine and no visible antenna,
presumably 701 ( adult female). Bottom two images feature an individual with equal eye
shine and an obvious antenna even from a distance, presumably 953 ( pup of the year). ..... 32
Figure 20. Kit fox capture and den locations at the Hwy 58 study site, California. ..................... 36
Figure 21. Desert kit fox with a GPS collar at the Hwy 58 study site, California. ....................... 36
Figure 22. Conceptual movement patterns of individuals among populations within the San
Joaquin kit fox metapopulation. Blue dots are source populations. White dots are non-source
populations. Roads are solid black lines. Three possible connectivity zones show
movement between source populations ( blue dashed line), between source and non- source
populations ( green dashed line) and between non- source populations ( red dashed line). This
simple conceptual model shown assumes movement is typically between nearest
populations. ........................................................................................................................... 43
Effects of Four- Lane Highways List of Tables
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LIST OF TABLES
Table 1. Captured fox data. ........................................................................................................... 10
Table 2. Collared fox data. ............................................................................................................ 25
Table 3. Summary of crossings via telemetry and visual observation. ......................................... 25
Table 4. Swift fox detections and crossing activity. ..................................................................... 27
Table 5. Attributes of culverts with swift fox detections. ............................................................. 28
Table 6. Species detections in culverts. ........................................................................................ 29
Table 7. Summary of crossings detected via telemetry. ............................................................... 31
Table 8. Summary of crossings detected via cameras. ................................................................. 31
Table 9. Short- term solutions for existing roads and long- term solutions for roads that eventually
will be upgraded with additional lanes of traffic. ................................................................. 45
Effects of Four- Lane Highways Disclaimer
Western Transportation Institute Page xi
DISCLAIMER
The contents of this report reflect the views of the authors who are responsible for the facts and
the accuracy of the data presented herein. The contents do not necessarily reflect the official
views or policies of the State of California. This report does not constitute a standard,
specification or regulation.
For individuals with sensory disabilities, this report is also available in Braille, large print, on
audio cassette, or computer disks, if requested. To obtain a copy of the report in an alternate
format, please call or write to the Division of Research and Innovation, P. O. Box 942873, MS-
83, Sacramento, CA 94273- 0001, 916- 654- 8899, or use the CA Relay Service TTY number: 1-
800- 735- 2929, or dial 711.
Effects of Four- Lane Highways Acknowledgments
Western Transportation Institute Page 12
ACKNOWLEDGMENTS
The authors acknowledge Dave Hacker, previously of Caltrans and now with California Fish and
Game, who initiated this work. Harold Hunt, Caltrans, manager of this multi- year effort was a
pleasure to work with.
The Endangered Species Recovery Program team, including Samantha Bremner- Harrison,
Stephen Harrison, Christine Van Horn Job, and volunteers, provided handling training and
offered a wealth of knowledge and expertise. Scott Phillips of ESRP assisted with the
preparation of some figures. We thank Colorado Division of Wildlife, Colorado Department of
Transportation, South Dakota Department of Transportation, and Badlands National Park for
their cooperation. For assistance in the field, we are grateful to Deb Ackley, Ryan Munes,
Patrick Myers, Paul Roghair and Brian Smith, as well as numerous staff of the aforementioned
agencies.
We also thank Andrew Scott, editor, and the staff at the Western Transportation Institute for their
administrative and technical support.
Effects of Four- Lane Highways Background
Western Transportation Institute Page 1
1. BACKGROUND
1.1. Project purpose
Roads have the potential to negatively impact wildlife populations directly ( e. g., vehicle strikes,
habitat loss, habitat fragmentation) and indirectly ( e. g., changes in prey availability, changes in
predator abundance) ( Forman and Alexander 1998; Bjurlin and Cypher 2003; National Research
Council 2005). In the case of the federally endangered and California state threatened San
Joaquin kit fox ( Vulpes macrotis mutica), these impacts could result in mortality, reduced
productivity or reduced genetic exchange, among other detrimental effects ( Bjurlin and Cypher
2003). In short, the long- term persistence of the San Joaquin kit fox may be at risk in roaded
habitats.
At least 549 km ( 341.3 mi) of highways through San Joaquin kit fox habitat are slated for
widening from two to four lanes, some of which will also include median barrier construction
( Clevenger 2005). In an effort to maintain habitat connectivity for the San Joaquin kit fox,
California Department of Transportation ( Caltrans) has begun incorporating culvert- like conduits
as wildlife crossing structures into these highway projects ( Clevenger 2005). Limited
information is available on whether kit fox use below grade passages such as culverts ( Bremner-
Harrison et al. 2007), design parameters that might facilitate their use, or what rate of passage is
needed to offset habitat connectivity losses ( Clevenger 2005). Data collected thus far suggest that
San Joaquin kit foxes enter culverts ranging in size from 33 cm x 61 cm ( 12.9 in x 24.0 in)
( height x width) to 185 cm x 170 cm ( 72.8 in x 66.9 in) but do not use them to cross the road,
and confirmed vehicle strikes further suggest kit foxes attempt to cross at- grade ( Bremner-
Harrison et al. 2007; B. Cypher, Endangered Species Recovery Program, pers. comm.). This final
report details four field studies conducted between September 2007 and January 2010. Swift fox
( Vulpes velox) were studied in Colorado and South Dakota ( Chapter 2). Desert kit fox ( Vulpes
macrotis arsipus) were studied in California ( Chapter 3). Conclusions are summarized in
Chapter 4. Mitigation recommendations for San Joaquin kit fox in relation to four- lane
highways, along with future research recommendations, are presented in Chapter 5.
This report uses several different terms pertaining to structures that allow wildlife to cross under
highways. Caltrans defines a “ culvert” as a closed conduit which allows water to pass under a
highway ( The Caltrans Highway Design Manual 2009). The term “ culvert” is used widely in this
report since the main purpose of the structures that we monitored was for drainage rather than the
movement of wildlife, although wildlife has been documented to use them. In this report, the
term “ wildlife crossing structure” pertains to a structure designed with wildlife needs in mind.
Collectively, the terms “ below grade passage” or “ below grade crossing opportunity” are used to
denote any structure beneath the grade of the road that allows wildlife to pass from one side of
the highway to the other, regardless of the original intent for its function.
1.2. Study approach
Due to limited evidence of San Joaquin kit fox use of below grade passages in relation to four-lane
highways ( Bremner- Harrison et al. 2007), surrogate species were selected to boost data
collection potential. We consider data collected on swift fox and desert kit fox to be pertinent for
making mitigation recommendations in regard to four- lane highways to benefit long- term San
Joaquin kit fox recovery ( Kociolek and Clevenger 2007; report prepared as part of this contract).
Effects of Four- Lane Highways Background
Western Transportation Institute Page 2
Swift fox were studied along Interstate 70 ( I- 70) near Limon in eastern Colorado and along
Interstate 90 ( I- 90) near Wall in southwestern South Dakota. Desert kit fox were studied along
California State Highway 58 ( Hwy 58) near Barstow in southern California. The aim of these
companion studies was to investigate the movements and crossing behavior of swift and desert
kit foxes around four- lane highways to make inferences for San Joaquin kit foxes. Specific
objectives of the studies included:
 To determine if four- lane divided highways inhibit fox movements;
 To quantify fox crossing rates of four- lane highways; and
 To determine the attributes of below- grade passages foxes use to cross four- lane
highways.
During the first field season, Tellus Mini GPS/ UHF ( Geographic Positioning System/ Ultra High
Frequency) collars manufactured by TVP Positioning AB ( also known as Televilt or Followit) in
Sweden were deployed on ten swift foxes in Colorado and five desert kit foxes in California.
These collars were intended to 1) be trackable via UHF at certain programmed times each day,
and 2) to drop off the animal on a specified date at which time the GPS- gathered spatial data
could be downloaded from the units. Several collars were range tested in Colorado and
California prior to deployment and were detectable up to approximately 1 km ( 0.6 miles).
Subsequent collar limitations and malfunctions are discussed in Chapters 2 and 3.
The work conducted in 2007– 2008 did not produce enough data to inform the needs of this
project, therefore a second field season was planned. Due to the experimental nature of
GPS/ UHF collars that are small and lightweight enough for swift/ kit fox use, however, proven
VHF ( Very High Frequency) technology was instead used during the second field season. While
VHF is more labor intensive and results in fewer data points, the collars are less costly and their
use allows the collection of some real- time data on fox movements relative to the highway.
There would have been a distinct advantage for conducting a second field season ( 2008– 2009) in
the same study areas ( e. g., establishment of local contacts, culverts already inventoried, etc.).
There was also the possibility that previously GPS- collared foxes could be re- captured during the
second season trapping effort, enabling retrieval of GPS data from the 2007– 2008 effort. A stop
work order pursuant to Governor Schwarzenegger’s Executive Order S- 09- 08 relating to
California’s budgetary problems hampered efforts for a 2008– 2009 field season ( H. Hunt,
Caltrans, pers. comm.).
By the time the second field season began in spring 2009, we were contacted by Badlands
National Park to study its recently reintroduced swift fox population near I- 90. The swift fox
study area was switched to South Dakota mainly because more effort could be put on monitoring
rather than trapping/ collaring. Also, since more than a year and a half had elapsed since foxes
were collared in Colorado, there was no guarantee that they still inhabited the study area or were
still alive. Swift foxes typically live four to five years in the wild and they were adults when they
were collared.
The California desert kit fox study area did not change, however, attempts to capture foxes
during the second season were unsuccessful possibly due to drought and a reduced prey base ( T.
Esque, U. S. Geological Survey, pers. comm.). Funds that would have been used for California
monitoring were instead transferred to the South Dakota effort to conduct a short- term fencing
experiment ( Section 2.2).
Effects of Four- Lane Highways Background
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During both field seasons, below- grade passages were monitored with cameras and/ or sand track
beds. Landscape and passage attributes were also collected.
Effects of Four- Lane Highways Swift Fox Studies
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2. EFFECTS OF FOUR- LANE HIGHWAYS ON SWIFT FOX
2.1. First field season ( October 2007 to January 2008), Colorado
2.1.1. Study area
The study area was focused on I- 70, a four- lane divided highway in eastern Colorado, which is
surrounded by large native tracts of prime swift fox habitat ( C. Cooley, Area Habitat Biologist,
Colorado Division of Wildlife, pers. comm.) ( Figure 1). There is a viable population core of
swift fox in Colorado ( Stephens and Anderson 2005) and a variety of below- grade passages exist
within the selected road section. See further discussion of site selection criteria in Kociolek and
Clevenger ( 2007).
Figure 1. View of study area looking east.
The study area was composed of two road sections located between the towns of Agate ( Exit
340) and Genoa ( Exit 370). The study area west of Limon ( Elbert County) spanned
approximately 8.2 km ( 5.1 mi) from mile post ( MP) 349.5 to MP 354.6 ( Figure 2). The area east
of Limon ( Lincoln County) spanned approximately 4.3 km ( 2.7 mi) from MP 365.4 to MP 368.1
( Figure 3). Average annual daily traffic volume was approximately 8,800 to 11,200 vehicles in
2007, 2,000 to 3,000 of which were trucks ( Colorado Department of Transportation 2009).
Permission to conduct the study was obtained from the Colorado Department of Transportation.
Figure 2 and Figure 3 illustrate trapping locations; animals that were captured, tagged and/ or
collared; and existing below- grade passages that were monitored. Collared foxes are depicted
with a circle ( female) or a triangle ( male). The label “ CH” followed by a number indicates the
factory- programmed channel number which corresponds to a particular UHF frequency. Below-grade
passages are alphanumerically coded with a C, R or U to represent a concrete box culvert,
Effects of Four- Lane Highways Swift Fox Studies
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a reinforced concrete pipe culvert, or an underpass, respectively; numbers refer to nearest one-tenth
of a mile post.
Effects of Four- Lane Highways Swift Fox Studies
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Figure 2. Study area west of Limon, Colorado.
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Figure 3. Study area east of Limon, Colorado.
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2.1.2. Methods
2.1.2.1. Trapping and collaring
In October 2007, swift foxes were captured using live traps ( 81 x 25 x 30 cm [ 32 x 10 x 12 in.];
single door; Tomahawk Equipment Company, Tomahawk, Wisconsin USA) and ( 81 x 25 x 30
cm; single door; Havahart- Woodstream Corporation, Lititz, Pennsylvania USA) under a
scientific collector’s permit (# 07TR1226) and with assistance from the Colorado Division of
Wildlife. Private landowner access and trapping permission was obtained. Traps were retrofitted
according to Moehrenschlager et al. ( 2003) and handling procedures were approved by Montana
State University’s Institutional Animal Care and Use Committee. Each trap was covered with a
canvas cloth and/ or green– brown plastic tarpaulin to provide shelter from the elements and to
simulate den conditions for captured animals. Bait consisted of a mixture of road- killed
pronghorn, chicken parts, mackerel, canned cat food, and hamburger. Traps were set
approximately one hour before sunset and checked at sunrise the following morning. Trapping
efforts were focused along barbed- wire fence lines and in pastures within 0.8 km ( 0.5 mi) of I- 70
in road sections with a variety of below- grade passages. In some cases, animals were trapped as
far as 1.6 km ( 1 mi) from I- 70. Captured foxes were kept in a cloth bag and physically restrained
without chemicals. Trapped foxes were weighed, sexed, aged, ear tagged, and dye marked, and
hair samples were taken.
2.1.2.2. Tracking and GPS data
Ten of the trapped foxes determined to be adults were fitted with Tellus Mini GPS/ UHF collars.
Collars were factory programmed to obtain a location fix via satellite every eight hours ( three
positions per day) and to drop off in 90 days. Collars are designed such that once they are
retrieved, GPS data can be downloaded. To obtain real- time data in the interim, attempts were
made to track via UHF during pre- programmed beacon times at least once, but more often
multiple times, weekly. Tracking via UHF was unsuccessful. A single 24- hour monitoring was
also conducted to ensure the collars were not transmitting at an unspecified time.
Due to the inability to track collars via UHF, an unexpected re- trapping effort ensued in an
attempt to retrieve collars from foxes prior to programmed drop- off dates. From 7 to 20 January
2008, attempts were made to recapture collared foxes near their original capture locations and
den sites. Infrared remote trigger cameras ( Reconyx PM35 or PM35M13 Silent Image
Professional 1.3 megapixel monochrome; Reconyx, Inc., Holmen, Wisconsin, USA) were used
to determine if any collared foxes were visiting traps.
2.1.2.3. Below- grade passage monitoring
All below- grade passages within 1.6 linear highway kilometers ( 1 mi) of each collaring location
were identified. Each was named to represent its location along the highway by estimating the
nearest one- tenth of a mile. The distribution of the monitored passages is depicted in Figure 2
and Figure 3.
There were a total of 24 below- grade passages in the two study areas combined:
 six square- shaped concrete box culverts ranging in size from 234 x 305 cm ( 92 x 120 in;
height x width) to 488 x 488 cm ( 192 x 192 in)
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 17 oval, round or semi- round ( i. e., flat bottomed) reinforced concrete pipe culverts
ranging in size from 28 x 84 cm ( 11 x 33 in) to 152 x 152 cm ( 60 x 60 in)
 one underpass
In some cases, there were multiple culverts immediately adjacent to one another. In total, there
were 19 locations in the two study areas combined:
 C366.4 is a double culvert ( i. e., two culvert entrances side by side).
 R353.5 and R354.3 are double culverts.
 R354.1 is a triple culvert ( i. e., three culvert entrances side by side).
 All other culverts and the underpass were stand- alone structures.
Sand track beds and/ or cameras were installed at each passage to be monitored. The use of a
track bed versus a camera was primarily dictated by the size of the structure and prevailing
winds. Cameras were generally installed in concrete box culvert situations but a temporary
camera was used in reinforced concrete pipe culvert situations as needed to confirm track
identifications. From 29 October 2007 to 10 January 2008 below- grade passages were monitored
for fox activity one to two times per week. Landscape variables and attributes were recorded for
each below- grade passage for future analysis.
2.1.2.4. Barrier assessment
Linear features that might act as barriers to fox movements were recorded along the entire length
of the study area from Agate ( Exit 340) and Genoa ( Exit 370).
2.1.3. Results
2.1.3.1. Trapping and collaring
Ten adult foxes, six females and four males, were captured and fitted with GPS collars ( Table 1).
Six of the collared foxes inhabited the area east of Limon and four inhabited the area west of
Limon. Individuals believed to be young of the year were not collared.
Effects of Four- Lane Highways Swift Fox Studies
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Table 1. Captured fox data.
MILE
POST CHANNEL GENDER
MAGNET
REMOVED
CAPTURE
DATE
EXPECTED COLLAR
DROP OFF DATE
EAR TAG
NO. DYE PATTERN
east of Limon
366 54 F 8- Oct- 07 8- Oct- 07 6- Jan- 08 6352 adult 1
367 56 F 9- Oct- 07 9- Oct- 07 7- Jan- 08 6353 adult 2
367 58 F 9- Oct- 07 9- Oct- 07 7- Jan- 08 6350 adult 3
367 60 M 10- Oct- 07 10- Oct- 07 8- Jan- 08 6354 adult 4
367 62 M 12- Oct- 07 19- Oct- 07 10- Jan- 08 6358 adult 10
366 64 M 9- Oct- 07 9- Oct- 07 7- Jan- 08 6341 adult 6
west of Limon
350 66 F 11- Oct- 07 14- Oct- 07 10- Jan- 08 6355 adult 5
353 68 F 12- Oct- 07 16- Oct- 07 10- Jan- 08 6356 adult 9
353 70 M 12- Oct- 07 17- Oct- 07 10- Jan- 08 6357 adult 9*
350 72 F 12- Oct- 07 17- Oct- 07 10- Jan- 08 6343 adult 8
* mistakenly given the same dye mark as other fox in the area
Other foxes not collared but tagged
352 NA F
not collared;
young of year 16- Oct- 07 NA 6342 young 6
366 NA F
not collared;
quota met 19- Oct- 07 NA 6359 adult 11
366 NA M
not collared;
quota met 19- Oct- 07 NA 6360 adult 12
2.1.3.2. Tracking and GPS data
Attempts at UHF tracking during pre- programmed beacon times were almost completely
unsuccessful with the exception of obtaining a weak signal from one collar ( Channel [ CH] 54)
on two occasions in the entire three- month period. Both detections were on the side of the
highway that the animal was collared. Collars failed to drop off in 90 days as programmed by the
manufacturer. Images of two collared individuals were obtained days after the factory
programmed drop- off date, illustrating the collars did not drop off as intended ( Figure 4 and
Figure 5).
One ( CH66) of ten collars was successfully recovered during recapture efforts and data were
downloaded. None of the 393 data points obtained between 15 October 2007 and 10 January
2008 are on the opposite side of I- 70 from original capture location. These data imply that this
four- lane highway may have acted as a barrier for this adult female during the study period. It
should be noted, however, that no location points were obtained on five days during the 88- day
period. Downloaded GPS data was reformatted into a KML file and imported into Google Earth
( Figure 6). See Section 2.1.3.3 for discussion of possible culvert use by this individual.
Effects of Four- Lane Highways Swift Fox Studies
Western Transportation Institute Page 11
Figure 4. Remotely triggered image taken on 15 January 2008, eight days past programmed drop- off date.
After several attempts, this fox was not recaptured.
Figure 5. Remotely triggered image taken on 14 January 2008, four days past programmed drop- off date.
This female fox ( CH66) was recaptured on 18 January 2008.
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Figure 6. Seasonal home range of an adult GPS- collared female swift fox ( CH 66) in relation to I- 70 west near
Limon, Colorado. Triangles represent GPS location fixes. This location is in the upper left quadrant of the
western study area map.
2.1.3.3. Below- grade passage monitoring
Twenty- four below- grade passages at 19 different locations were monitored 21 times between 29
October 2007 and 10 January 2008. In addition to swift fox, birds— including an accipiter hawk
( Accipiter sp.), small rodents ( e. g., mice), hares or rabbits ( family Leporidae), raccoon ( Procyon
lotor), striped skunk ( Mephitis mephitis), red fox ( Vulpes vulpes), coyote ( Canis latrans) and
domestic cattle were detected in or near entrances of passages by their tracks or camera images
( Figure 7 and Figure 8). In some cases, tracks could not be identified.
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Figure 7. Number of instances of species ( or groups) detected in or near entrances of below- grade passages in western study area.
0
1
2
3
4
5
6
7
8 R349.5
R350.6
R350.8
U350.9
R350.9
R351.2
R351.3
R351.5
C353.2
R353.4 W only
R353.5A
R353.5B
R353.7
R354.1A
R354.1B
R354.1C
R354.3A
R354.3B
C354.6
Number of instances ( N)
Below- grade passage
Western study area
Swift fox crossing
Swift fox
Coyote crossing
Coyote
Red fox
Unidentified canid
Raccoon or striped skunk
Hare or rabbit
Rodent
Unidentified tracks
Cattle
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Figure 8. Number of instances of species ( or groups) detected in or near entrances of below- grade passages in
eastern study area.
There were several instances where swift fox tracks entered a culvert partway and retreated.
Complete crossings by swift fox through two different reinforced concrete pipe culverts were
documented five times via tracks and/ or image data. Complete crossings are defined as the
presence of tracks at both entrances traveling in the same direction. While there were six
instances indicating complete crossings by coyote, red fox or an unidentified canid, only the
unidentified canid crossing occurred in a culvert in which a complete swift fox crossing also took
place ( in R368.1).
On some monitoring days, standing water, snow drifts, snow- packed entrances, or frozen track
beds precluded the ability to detect tracks in some below- grade passages ( Figure 9). The two
culverts in which complete swift fox crossings were detected ( R368.1 and R351.2) did not have
these issues.
Eastern study area
0
1
2
3
4
5
6
7
8
9
C365.4
C366.4A
C366.4B
C367.7
R368.1
Below- grade passage
Number of instances ( N)
Swift fox crossing
Swift fox
Coyote crossing
Coyote
Red fox crossing
Red fox
Unidentified canid crossing
Unidentified canid
Raccoon or striped skunk
Hare or rabbit
Rodent
Unidentified tracks
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Figure 9. Number of instances when track bed condition precluded track detectability. There was an instance
where a culvert was not monitored because of an unsafe traffic situation.
Probable swift fox tracks were originally detected at R351.2 ( western study area) on 7 November
2007 and again on 13 November 2007; both sets of tracks indicated the fox moved just inside or
around the entrance of the culvert but not through. On 21 November 2007, swift fox tracks were
found at both ends of the culvert heading in the same direction indicating a complete crossing
through the culvert. On several other occasions swift fox tracks were found only on one side or
the other. To confirm tracks at R351.2 as swift fox tracks, a temporary camera was placed at one
entrance on 28 November 2007. On 14 December 2007, an unmarked swift fox was documented
on camera ( Figure 10) and tracks at both ends were heading in the same direction. It is
speculated that this fox may have been hunting rodents that have been detected in this structure
( Figure 11).
Western and eastern study areas
0
1
2
3
4
5
6
7
C365.4
C366.4A
C366.4B
C367.7
R368.1
R349.5
R350.6
R350.8
U350.9
R350.9
R351.2
R351.3
R351.5
C353.2
R353.4 W only
R353.5A
R353.5B
R353.7
R354.1A
R354.1B
R354.1C
R354.3A
R354.3B
C354.6
Below- grade passage
Number of instances ( N)
Track detectability impaired
Not checked due to traffic
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Figure 10. Swift fox documented inside reinforced concrete pipe culvert ( R351.2) confirms a crossing
occurred via the culvert. Snow can be seen in foreground.
Figure 11. Another view of the individual in Figure 10 confirms it is an unmarked fox. This individual
appears to be attracted to the seam where a rodent might live.
On 21 December 2007, an unmarked fox was documented on camera in R351.2 ( Figure 12) and
tracks at both ends indicated it was a complete crossing. It is unknown whether the foxes
documented on 14 December and 21 December 2007 is the same individual.
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Figure 12. A second instance of a swift fox documented crossing via R351.2.
One more complete crossing by a swift fox was noted in R351.2 on 6 January 2008. The R351.2
structure and adjacent landscape are pictured in Figure 13.
Figure 13. View of R351.2 entrance ( 152 cm [ 60 in]) in diameter ( left) and adjacent landscape ( right).
A total of six reinforced concrete pipe culverts and one underpass exist within CH66’ s home
range ( Figure 6). It is unknown whether the R351.2 crossings on 21 November 2007 or 6 January
2008— documented by tracks only— were by CH66.
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The only other possible complete crossing by swift fox was detected in R368.1 ( eastern study
area) on 19 November 2007. R368.1 spans a two- lane unpaved frontage road in addition to the
four- lane divided highway ( Figure 14).
Figure 14. View of both entrances of R368.1; 52 x 104 cm ( 20.5 x 41 in; height x width) at eastbound entrance
( left) and 93 x 118 cm ( 36.5 x 46.5 in) at westbound entrance ( right).
2.1.4. Discussion
GPS/ UHF collar malfunctions severely limited the amount of data garnered about swift fox
movements in relation to I- 70. Data downloaded from a single retrieved collar ( CH66) indicates
the four- lane divided highway may be acting as a barrier for at least this one adult female. None
of the 393 location points obtained over an 88- day period were on the opposite side of the
highway from where the animal was collared. Habitat may have played a role in CH66’ s
movements. Its home range encompassed ample grass– forb rangeland and the habitat across the
highway included more shrub cover and more waterways, in addition to a rail line ( Figure 2).
An incidental sighting of a crossing at- grade and swift fox tracks found in snow illustrate that
some swift fox do attempt to cross I- 70. These successful crossings took place where no solid
median barriers exist.
Monitoring all the below- grade passages within one linear mile of all collaring locations yielded
evidence that at least two individuals used culverts to cross under I- 70. The two culverts where
swift fox crossings were detected are 27.3 km ( 17 mi) apart, a distance much greater than
individual foxes in the area are known to travel, at least when not actively dispersing ( Figure 6).
The dimensions of R351.2 ( 152 cm [ 60 in] in diameter) and R368.1 ( 52 x 104 cm [ 20.5 x 41 in]
– 93 x 118 cm [ 36.5 x 46.5 in]) fall within the size range of culverts studied by Bremner-
Harrison et al. ( 2007) where no complete crossings by foxes were documented. It is likely that
the presence of prey ( e. g., rodents) plays a role in attracting foxes to these culverts. Some swift
fox appear to use some reinforced concrete pipe culverts to cross under four lanes of highway
and as many as, the approximate equivalent of, six lanes when considering culverts that span a
frontage road in addition to the highway.
Standing water, snow drifts, snow- packed entrances or frozen track beds made some culverts
impassable or made tracks indiscernible on some days. Tumbleweed chronically persists in some
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structures although none of the structures monitored were completely inaccessible due to its
presence.
2.2. Second field season ( May 2009 to January 2010), South Dakota
2.2.1. Study area
The study area was centered along I- 90, a four- lane divided highway north of Badlands National
Park in southwestern South Dakota. The area of interest extended beyond the right- of- way to the
extent a radio telemetry signal from a collared fox could be detected, approximately 1.6 km ( 1
mi). Average daily traffic volume in 2008 ranged from approximately 5,000 to 6,000 vehicles,
1,400 to 1,500 of which were trucks ( South Dakota Department of Transportation 2010). The
surrounding area is largely considered to be swift fox habitat and is composed of public and
private mixed grass prairie ranchlands ( Russell 2006). Swift fox reintroductions began in the area
in 2003 ( Schroeder 2007). The Western Transportation Institute collaborated with Badlands
National Park to take advantage of the fact that more than 100 swift foxes in the area were
already radio collared ( G. Schroeder, Badlands National Park, pers. comm.). Badland National
Park’s handling procedures were reviewed and approved by Montana State University’s
Institutional Animal Care and Use Committee. Permission to conduct the study was obtained
from the South Dakota Department of Transportation.
Swift fox monitoring was focused on three discrete subsections along a 41.8- km ( 26- mi) section
from MP 117 to MP 143 ( Figure 15). The subsections either are known to be inhabited by swift
fox or are considered likely for habitation ( G. Schroeder, Badlands National Park, pers. comm.).
Subsections I, II, and III roughly span MP 117 to MP 123, MP 126 to MP 132.8, and MP 136.5
to MP 143, respectively. The red zones in Figure 15 indicate areas not likely to be inhabited by
swift fox ( G. Schroeder, Badlands National Park, pers. comm.) and, therefore, were not
monitored.
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Figure 15. Study area along I- 90, east of Wall, South Dakota.
This highway section has a grassy median with no median barrier. A variety of below- grade
passages, including concrete pipe and box culverts, exist. There are no underpasses.
See Section 1.2 for more information regarding the timing and change of location of the second
swift fox field season.
2.2.2. Methods
2.2.2.1. Nocturnal VHF tracking
Badlands National Park biologists provided the Western Transportation Institute with VHF
frequencies of all their collared foxes, obviating the need to trap for this project alone. They also
provided all known natal den locations within the I- 90 corridor. There was an understanding that
Park biologists would collar additional foxes if/ when any uncollared animals were observed in
our area of interest.
The goal of this VHF tracking effort was determine the location of a given fox relative to I- 90.
That is, no attempt was made to pinpoint the location of the actual fox but rather to determine
whether the fox was north of I- 90, south of I- 90, or in the grassy median. The majority of
telemetry attempts were conducted from overpasses and shoulders of I- 90. Telemetry was also
conducted from adjacent bisecting roads but no farther than 1.6 km ( 1 mi) from the highway
corridor, as needed, to pick up a signal. Multiple passes were made along I- 90 from MP 117 to
MP 143 during each telemetry session. By performing multiple passes in a session, data on the
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movements and crossing behavior of individual foxes could be obtained. An R- 1000 telemetry
receiver ( Communications Specialists, Inc., Orange, California, USA), three- element folding
yagi and a vehicle- mounted omni- directional dipole antenna ( Advanced Telemetry Systems,
Isanti, Minnesota, USA) were used for this purpose. Visual observations of foxes were also
noted.
2.2.2.2. Below- grade passage monitoring
All below- grade passages within the three discrete subsections were identified. Alphanumeric
codes were assigned to signify location of culverts relative to mileposts.
There are a total of 51 culverts in the three subsections combined. Two box culverts have high
human activity and, therefore, were not monitored.
The remaining 49 culverts are composed of:
 four square- shaped concrete box culverts ranging in size from 213 x 213 cm ( 84 x 84 in;
height x width) to 358 x 302 cm ( 141 x119 in);
 43 round reinforced concrete pipe culverts ranging in size from 43 x 46 cm ( 17 x 18 in) to
213 x 213 cm ( 84 x 84 in); and
 two elliptical or semi- round culverts ranging in size from 56 x 91 cm ( 22 x 36 in) to 66 x
109 cm ( 26 x 43 in).
Culverts vary in the number of lanes they span ( i. e., two lanes on each side of highway, opening
into the median; four lanes; and six lanes, including exit/ entrance ramps).
Sand track beds were installed at terminal ends of each culvert to be monitored ( i. e., if a culvert
was a two- lane culvert pair and opened into the median, only the side entrances had track beds
and the median entrances did not). From 25 June to 30 October 2009 track beds were monitored
for fox activity one to two times per week, unless they became inoperable due to
weather/ hydrological events.
Six cameras were employed. Three were semi- permanently installed in culverts from early to
mid- July to 19 November 2009, ranging from 120 to 131 days each. The other three cameras
were temporarily installed at ten weather/ hydrology- affected culverts, ranging from five to 69
days during the study period. See Appendix A for complete monitoring scheme. Landscape
variables and attributes were recorded for each culvert within 1.6 linear kilometers ( 1 mi) of
known natal dens for future analysis. Monitored culverts and known natal dens are shown in
Figure 16.
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Figure 16. Distribution of culverts ( black rings) and natal den locations ( red balloons). For ease of viewing,
only culvert entrances on the eastbound side of the highway (- E) are shown. B – concrete box culvert, TB –
concrete tunnel box culvert ( discovered to have high human use, therefore, not monitored), R – reinforced
concrete pipe culvert. The elliptical- shaped reinforced concrete pipe culvert label is not shown on map.
2.2.2.3. Roadkill monitoring
Badlands National Park biologists shared swift fox roadkill observations. Monitoring is fairly
consistent since they drive the highway most days twice per day ( to and from work). They also
receive roadkill reports from the public. In addition, we reported swift fox roadkills to Park
biologists.
2.2.2.4. Experimental fencing
There was an opportunity to determine if it is possible to funnel foxes to culverts and encourage
below- grade crossings. After the regularly scheduled field season ended on 31 October 2009,
fencing was installed along both right- of- way fence lines for approximately 2.7 km ( 1.7 mi)
between the southeastern entrance/ exits ramps of Exit 127 ( near MP 128) and a westbound side
pullout ( near MP 129.6). Permission was obtained from the South Dakota Department of
Transportation before installation.
Fencing consisted of 122 cm ( 48 in) tall chicken wire ( 2.5 cm [ 1 in] mesh), metal hog rings to
attach to the existing barbed- wire fence line, 10- gauge metal landscape staples 5 x 20 cm ( 2 x 8
in) to anchor mesh to the ground, and t- posts to provide attachment points for fencing leading to
culvert entrances ( Figure 17).
The fenced area included two reinforced concrete pipe culverts, one that spans all four lanes
( R128A) and one that is a two- lane pair opening into the median ( R128B). A chicken- wire tunnel
connected culvert entrances of the two- lane culvert pair in the open median.
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Cameras were installed at all six culvert entrances in the fenced section. Nocturnal VHF tracking
was conducted within the fenced area and up to 3.2 km ( 2 mi) in either direction multiple times
per week, weather permitting. All known frequencies were scanned during each session to
determine if new collared foxes were in the area. Emphasis was put on tracking those collared
foxes known to be in the area. The plan was to monitor fox movements for two months,
commencing after installation was completed in late November 2009. Local wisdom indicated
that the greatest snow accumulations typically occur in February.
Effects of Four- Lane Highways Swift Fox Studies
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Figure 17. Fence installation ( clockwise from top left: a vehicle- mounted spool aids in laying out ~ 5.6 km ( 3.5
mi) of fencing; several inches of mesh stapled to the ground creates a barrier to digging under the fence line;
t- posts enable angling the mesh away from the right- of- way fence line ( foreground) to the culvert entrances
( location of workers in the mid- ground).
Effects of Four- Lane Highways Swift Fox Studies
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2.2.3. Results
2.2.3.1. Nocturnal VHF tracking
A total of eight radio- collared foxes that inhabited the study area were tracked via VHF over the
course of 55 sessions between 8 June and 30 October 2009 ( Table 2). During the course of the
season, several uncollared adult foxes were observed near I- 90 in the study area; however,
attempts to capture these individuals were unsuccessful.
Table 2. Collared fox data.
Den ID Fox ID Frequency Gender Age
773
773 164.814 M adult
463 167.666 F adult
440
440 165.020 F adult
577 165.151 M adult
701
701 165.282 F adult
715 164.091 M adult
unknown 568 164.543 F adult
unknown 768 164.803 M adult
Tracking typically occurred during dusk and hours of darkness when foxes are most active ( i. e.,
between 8 pm and 2 am) although some daytime tracking was conducted as well. Not all collared
foxes were able to be located during every session. Radio signals were affected by fox location
on the landscape, whether the fox was above or below ground, subtle changes in topography,
manmade objects, etc. Telemetry attempts ceased during periods of lightning, rain, and high
winds. Visual observations of at- grade crossings were documented. Table 3 summarizes known
crossings for each collared fox in the study area.
Table 3. Summary of crossings via telemetry and visual observation.
Den ID Fox ID
Total no. of
detections
( telemetry)
No. of 2- lane
crossings
( telemetry)
No. of 4- lane
crossings
( telemetry)
No. of 2- or 4-
lane at- grade
crossings also
visually
observed
Percent of all
detections on opposite
side of highway from
previous
773
773 79 13 28 3 35%
463 82 4 35 1 43%
440
440 63 14 19 0 30%
577 48 12 14 1 29%
701
701 99 6 36 6 36%
715 27 5 11 2 41%
unknown 568 79 28 23 15 29%
unknown 768 33 0 12 1 36%
Each collared fox was detected via telemetry an average of 64 times. On average, each fox was
located on the opposite side of the highway from its last known location 35 percent of the time.
Foxes were frequently observed within the right- of- way during tracking sessions. Successful
crossings as well as failed crossing attempts in the form of retreats were documented. No real-time
roadkills were observed.
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2.2.3.2. Below- grade passage monitoring
Frequent rain storms and subsequent ground saturation and flooding posed great challenges for
culvert monitoring via track beds. Despite attempts to replace tracking material and/ or improve
drainage with a pea gravel substrate beneath the sand, many of the track beds became inoperable
to the point of abandonment.
Of the 46 culverts without a semi- permanent camera, only 10 held the tracking substrate to
enable fairly consistent monitoring via track beds, although even these had periods of
inoperability ( i. e., due to wind scouring, skunk digging, etc.). Twenty- eight culverts were
severely affected by rain and/ or ground saturation thereby rendering track beds inoperable for all
or most of the study period. However, during the month of September, swift fox tracks were
documented in five of the affected culverts since tracking material remained in at least one
entrance while the other was underwater or washed out.
Swift foxes were detected in or near the entrances of eight different culverts ( Table 4) out of 49
that were monitored for some portion of the study period. Five with swift fox detections are
reinforced concrete pipe culvert sets ( i. e., paired culverts that span two lanes each and open into
the median). Only the entrances on the outer edge of the highway were monitored. The entrances
located in the median were not. There were several reasons for this approach: 1) safety issues
associated with highway traffic, 2) this study is interested in four- lane crossings, 3) the sheer
number of culverts to be monitored already posed a logistical challenge, and 4) most of the
culverts that opened into the median were on lower ground, thus, highly affected by
weather/ hydrology. The remaining three culverts with swift fox detections consisted of two
concrete box culverts that span four lanes and one reinforced concrete pipe culvert that spans six
lanes, including entrance/ exit ramps. Seven of the eight culverts with swift fox detections were
within 1.6 km ( 1 mi) of a known natal den.
There were a total of 19 fox detections in culverts ( 8 via tracks, 11 via camera images). In three
images, the fox did not enter the culvert. Of the remaining 16 detections, three were definitely
not complete four- lane crossings. Not including the six- lane culvert, one of the remaining twelve
detections appeared to be a complete four- lane crossing by an uncollared fox. It is unknown
whether the remaining eleven detections constituted complete four- lane crossings, but at least
three were complete two- lane crossings with seven additional two- lane crossings likely to have
occurred. It is possible that a complete six- lane crossing occurred, however, the fox could have
entered the culvert via a grate in the median, thereby, limiting certainty to a complete three- lane
crossing.
Due to the small sample size of fox crossings, statistical analysis was not possible. Attributes of
culverts with swift fox detections are listed in Table 5. Species detections in culverts are shown
in Table 6.
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Table 4. Swift fox detections and crossing activity.
Sub-section
Den Culvert
ID
No.
Lanes Evidence No.
Events Collared Direction
of travel
Track
and/ or
bed
condition
Complete
4- lane
crossing?
I
773
( mate
463)
R118C
2 + 2
open
median
tracks on E 2 NA
E to W E fair &
W inoperable
unknown;
( 2- lane likely)
E to W E poor &
W inoperable
unknown;
( 2- lane likely)
773
( mate
463)
R119B
2 + 2
open
median
tracks on E 1 NA W to E E & W good no;
( 2- lane likely)
image on E 1 unknown W to E W inoperable
unknown;
( at least one 2-
lane incomplete;
saw camera on
E and retreated)
773
( mate
463)
R119C
2 + 2
open
median
tracks on E 2 NA
E to W E & W good no;
( 2- lane likely)
W to E E poor &
W inoperable
unknown;
( 2- lane likely)
images on E 5
yes W to E
W inoperable
unknown
no
( juvenile?) W to E
unknown;
( 2- lane
complete)
yes W to E
unknown;
( 2- lane
complete)
unknown did not
enter no
no
( juvenile?) W to E
unknown;
( 2- lane
complete)
773
( mate
463)
R120A
2 + 2
open
median
tracks on E 1 NA W to E E poor &
W inoperable
unknown;
( 2- lane likely)
440
( mate
577)
R121C
2 + 2
open
median
images on E 3
unknown did not
enter NA NA
unknown did not
enter NA NA
no E to W W inoperable unknown;
( 2- lane likely)
440
( mate
577)
R121D
6
grated
opening
in
median
tracks on W 2 NA E to W E inoperable
& W fair
unknown;
( 6- lane possible
but unsure if
accessed via
grate in median;
3- lane complete)
II
none
known B126A 4 image
in middle 1 unknown E to W NA
unknown; ( only
hind half of body
pictured, unsure
if camera delay
or if animal
retreated when
saw camera)
701
( mate
715)
B130D 4 image
in middle 1 unknown
( juvenile?) unknown NA yes
III none
known - - none NA
Key: E and W refer to highway travel direction, i. e., eastbound side and westbound side, respectively.
Effects of Four- Lane Highways Swift Fox Studies
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Table 5. Attributes of culverts with swift fox detections.
Culvert
ID Shape H
( in)
W
( in)
No.
Lanes
Vis.
( 0- 1) Median Drop
inlets
Slope
to road
(%)
Hypotenuse
( ft)
Terrain
( 100 m)
Substrate at
entrance
Substrate
in
culvert
Culvert
follows
natural
creek?
R118C- E r 24 24 2 1 open no 20 18.5 rolling vegetation,
concrete concrete no
R118C- W r 24 24 2 1 open no 10 26.0 rolling
vegetation,
concrete,
water
sediment,
concrete,
water
no
R119B- E r 37 36 2 1 open no 20 43.0 flat
vegetation,
water,
concrete
concrete yes
R119B- W r 37 36 2 1 open no 10 19.5 rolling
vegetation,
water,
concrete
concrete,
water no
R119C- E r 24 25 2 1 open no 10 28.5 flat vegetation,
sediment
concrete,
sediment,
water
yes
R119C- W r 24 24 2 1 open no 15 21.0 rolling vegetation concrete,
water no
R120A- E r 24 24 2 1 open no 15 28.5 flat
vegetation,
rock,
concrete
concrete,
water yes
R120A- W r 18 18 2 3/ 4 open no 10 23.0 flat
vegetation,
water,
concrete
concrete,
water no
R121C- E
r
60 57 2 1 open no 10 30.0 rolling
vegetation,
sand,
rip rap,
metal wire
concrete yes
R121C- W
r
60 55 2 1 open no 10 20.0 flat
vegetation,
concrete,
water,
sediment
concrete,
sediment,
water
no
R121D- E
r
22 24 6 1/ 2
below,
concrete
grate
yes 20 71.5 rolling sediment concrete,
sediment yes
R121D- W
r
24 24 6 1/ 2
below,
concrete
grate
yes 20 30.0 rolling vegetation,
sediment concrete yes
B126A- E s 84 84 4 1 below yes 30 20.5 rolling vegetation,
concrete
vegetation,
sediment no
B126A- W s 84 84 4 1 below yes 30 5.5 rolling vegetation,
concrete
vegetation,
sediment no
B130D- E
s
84 84 4 3/ 4 below no 20 25.0 flat
concrete,
mud,
vegetation,
tumbleweed
concrete,
sediment,
water/ mud,
tumbleweed
no
B130D- W
s
84 84 4 3/ 4 below no 20 22.5 rolling
concrete,
mud,
vegetation,
tumbleweed
concrete,
sediment,
tumbleweed
yes
Key: Shape ( r – round, s – square); H – height, W – width; Vis. – visibility ( amount of light through distal
opening when viewed from proximal opening); Slope to road ( from culvert opening to road grade);
Hypotenuse ( distance of culvert opening to road); Terrain ( as viewed from culvert entrance looking 180
degrees away from highway). Additional attribute data, such as percent cover estimates, were collected but
not included here since small sample size precludes usefulness.
Effects of Four- Lane Highways Swift Fox Studies
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Table 6. Species detections in culverts.
Culvert
ID SWIFT FOX Leopard
frog
Snake
sp.
Bird
sp.
Bat
sp.
Mouse
sp.
Jackrabbit
or
Cottontail
Raccoon Skunk Porcupine Badger Red
fox
Domestic
cat Cattle Unknown
B117A c
R117B t t
R117C t t t
R117D t t
R118C t t t t
R119A t t
R119B t, c c
R119C t, c c
R119D c
R119E t
R120A t t
R120B t
R120C t t
R121A c
R121C c c c c c c c c
R121D t t
R122A t
R122B t t t t t
R122D t t
B126A c t t, c c c t, c t, c t, c t
R126B t t t
R127A t t t t t
R128A t t t
R128B t t, c t t t t
R129B t
R130B t
B130D c t c c c c c c t, c
R132A t t t t t t
E132B t t t t t
R136A t t t
R137A t t t t
R137B t t t t
R138A t t
R138B t t t t t t t
R138C t t t t
R139B t t t t
R139D t t t t
E140B t t t
R140C c c t, c t, c t c t
R141A t t t
R141B t t t
R142A t
R142B t
R142C t
Key: Detections via tracks ( t) and camera images ( c). Note: Culverts not listed in this table had no signs of wildlife presence.
Effects of Four- Lane Highways Swift Fox Studies
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2.2.3.3. Roadkill monitoring
Nine swift fox roadkills were documented on I- 90 between 22 June and 31 August 2009. Most of
these were believed to be juveniles although at least one sub- adult female was also struck.
2.2.3.4. Experimental fencing
The post- fencing monitoring began on 30 November 2009 but was terminated prematurely due
to a massive blizzard that affected the study area on 25 December 2009. I- 90 was shut down and
safe travel was not possible for several days. The snow sealed off culvert entrances and buried
the chicken wire fence, destroying some sections ( Figure 18). It was not feasible to dig out the
fenced study area to allow for culvert use. Travel conditions continued to be unsafe and,
therefore, precluded regular radio tracking. During the second week of January the decision was
made to terminate data collection given that the study area would likely continue to be affected
by winter weather issues.
Figure 18. Snow filled culvert entrances and negated the effectiveness of the fencing. T- posts delineate where
chicken wire fencing funneled to culvert entrances.
A total of 12 telemetry sessions were conducted within 3.2 km ( 2 mi) of the fenced study area
between 30 November and 30 December 2009. While all collared fox frequencies were scanned
during each session, a total of four foxes were detected during the fencing study ( Table 7).
Almost all detections were of 701 and her pup 953, which were often tracked to the median. On
10 December 2009, their den was found in the median about 68.6 m ( 75 yd) from the western
fence end. Interestingly, the foxes seemed to avoid the access afforded by western fence end,
possibly due to the existence of tall grass, and instead traveled more than 2.4 km ( 1.5 mi) to the
Effects of Four- Lane Highways Swift Fox Studies
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eastern fence end rather consistently ( P. Roghair, pers. comm.). This new den is in addition to
the 701 natal den pictured in Figure 16.
All crossings included in Table 7 were determined to be at- grade and around fence ends because
there was no camera evidence of culvert use on these days. Also 701 and 953 would not have
had access to their den via the two- lane culvert pair because a fence tunnel connected the two
median entrances providing no access from the median itself.
Table 7. Summary of crossings detected via telemetry.
Fox ID Gender/ age/ relationship
No. of session
days detected
No. of
detections
No. 2- lane
crossings
No. 4- lane
crossings
701 Female adult 12 59 12 7
953 Female pup of 701 9 44 10 2
568 Female adult 1 4 0 0
949 Female pup ( relationship unknown) 1 1 NA NA
Cameras were in place and functional from 30 November to 25 December 2009, when the snow
began accumulating in the blizzard. Soon thereafter, all cameras were dug out and removed with
the exception of one camera left at R128BE.
There was only one camera detection at the four- lane culvert R128A— on 12 December 2009 a
collared fox entered partway but then retreated. Therefore, there is no evidence of a successful
crossing via the four- lane culvert during the post- fencing period.
There were six series of crossing activities via R128B, the two- lane culvert pair system
connected by a chicken- wire tunnel in the median ( Table 8). All events appear to involve only
701 or her pup 953, based on two visual cues ( i. e., eye reflectivity and collar antenna condition).
One fox has conspicuously unequal reflectivity in its eyes and it is sometimes difficult to
ascertain the presence of a collar. We surmise this is 701, an adult whose antenna could have
been chewed off. The other fox has a prominent antenna consistent with that of a newly collared
juvenile ( 953). See Figure 19 for comparison.
Table 8. Summary of crossings detected via cameras.
Date
Fox
ID Direction of travel
1- Dec- 09 701 E to W
3- Dec- 09 701 E to W
701 W to E
6- Dec- 09 701 W to E
8- Dec- 09 953 E to W to E to W to partway E to W to E
31- Dec- 09 953 E to W*
* only a single camera was in use, other entrances were snow- packed
making a four- lane crossing improbable, however, no retreat was recorded
Effects of Four- Lane Highways Swift Fox Studies
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Figure 19. Top two images feature an individual with unequal eye shine and no visible antenna, presumably
701 ( adult female). Bottom two images feature an individual with equal eye shine and an obvious antenna
even from a distance, presumably 953 ( pup of the year).
2.2.4. Discussion
Part of the rationale for switching study areas from Colorado to South Dakota was the potential
benefit of being able to monitor more than ten foxes, which was the original stated project
objective. Badlands National Park is highly invested in monitoring the swift fox population that
resulted from reintroduction efforts. Despite attempts to collar more individuals whose ranges
encompass I- 90, the total number of regularly trackable foxes was limited to eight. Each of the
eight were tracked regularly ( Table 2) and I- 90 does not appear to be a barrier to movement for
these individuals.
Standing water or washouts of the tracking substrate made it impossible to discern culvert use of
many culverts throughout the season. Even so, there was documented fox use of culverts ( i. e.,
tracks and camera images). However, none were four- lane crossings through a reinforced
concrete pipe culvert, the most common culvert type in the area ( Table 4). The only four- lane
crossing was through a relatively large 213 x 213 cm ( 84 x 84 in) box culvert. Two- lane
crossings were the most common. It is possible that a six- lane crossing occurred but the
existence of an open grate in the median makes it impossible to confirm. The openness created
by the drop inlet may have simulated the two- lane culvert pair variety, making the crossing more
inviting than a closed culvert ( i. e., no opening into the median). Alternatively, it is possible that
the fox accessed the culvert midway in the median. The culverts that had evidence of swift fox
use also had evidence of prey species and other meso- predators ( Table 6).
Effects of Four- Lane Highways Swift Fox Studies
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Telemetry data and visual observations confirm that at- grade crossings are much more common
than below- grade crossings. For the eight foxes regularly tracked in this study, I- 90 is not an
obvious barrier to movement. Vehicle strike does appear to be a major threat to juvenile foxes
that den within the right- of- way or whose range encompasses I- 90. There were nine documented
roadkills on I- 90 in a span of approximately ten weeks. Seventeen additional roadkills were
documented on other roads monitored by Park biologists within a 30- week period. Park
biologists noted that the number of road killed swift fox pups seemed to increase in wet years
when vegetation was taller ( G. Schroeder, Badlands National Park, pers. comm.). The reason for
this is unclear. Possible explanations include foxes having greater difficulty observing
approaching traffic before entering the roadway, or foxes spending more time near or even on
roads to avoid dense vegetation.
The short- term experimental fencing study illustrated the possibility of funneling foxes toward
culverts. Neither of the culverts monitored post- fencing ( R128A and R128B) had any evidence
of swift fox use prior to fence installation ( Table 4). This is despite the fact that tracks beds were
mostly operable during the pre- fencing period ( May through October) and that snake species,
Leporidae sp. ( cottontail rabbit or jackrabbit), skunk, and raccoon were documented in them
( Table 6). The absence of swift fox in R128A and R128B during the pre- fencing period could be
partially explained by the greater than 1.6 km ( 1 mi) distance from 701’ s natal den. All but one
of the culverts that had documented fox use prior to fencing were within 1.6 km ( 1 mi) of a natal
den ( Table 4). There were no documented swift fox crossings post- fencing via R128A, a four-lane
culvert, however, 701 and her pup, 953, did make complete four- lane crossings via the two-lane
culvert pair with a chicken wire tunnel in the median ( R128B). It is uncertain if the new den
belonging to 701— found in the median of the fenced section in December— was created before
or after fence installation in November.
Budget constraints limited the length of fencing installed. Because foxes can easily travel more
than 2.7 km ( 1.7 mi) in a given night, the fencing probably did not pose much inconvenience to
many individual foxes. The only foxes that appeared to cross via the culvert post- fencing also
happened to live within the median of the fenced zone itself. The funnel effect of the fencing was
not particularly convenient for these individuals because the chicken wire tunnel prevented them
from accessing their den at the median opening between culverts.
The sample sizes in this study are too small and the monitoring regime too inconsistent for
rigorous statistical analysis. However, an opportunistic observation during the study suggested
that pressure may play a role in fox use of culverts. When a maintenance crew was re- tarring a
section of the highway during the pre- fencing period, it was noted that foxes used culverts
presumably as a way to avoid the sticky road grade surface ( B. Smith, pers. comm.). This may
suggest that, if pressured ( i. e., due to an obstacle such as a tar barrier), the probability of fox use
of culverts may increase.
Effects of Four- Lane Highways Desert Kit Fox Studies
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3. EFFECTS OF FOUR- LANE HIGHWAYS ON DESERT KIT FOX
3.1. First field season ( October 2007 to June 2008), California
3.1.1. Study area
The study area encompassed approximately 21.7 km2 ( 13.5 mi2) of the Mojave Desert in San
Bernardino County, California. The area is intersected by numerous non- paved access roads and
ephemeral washes. Habitat is dominated by xeric vegetation consistent with alkali desert scrub
habitat ( for further details of vegetation structure see Boarman and Sazaki 1996) and is within
the known range of the desert kit fox ( Vulpes macrotis arsipus) ( McGrew 1979; O’Farrell and
Gilbertson 1986).
The study area was bisected by an approximately 5.2- km ( 3.2- mi) section of California State
Highway ( Hwy) 58. The western boundary of this area was located approximately 15.5 km ( 9.6
mi) east of the Hwy 58/ Hwy 395 intersection while the eastern boundary was located
approximately 20 km ( 12.4 mi) west of Barstow. This section of Hwy 58 is a four- lane road with
a central dirt median and no median barrier. The average daily traffic volume measured at five
points in 2006 was 11,700 vehicles in both directions of travel.
Potential crossing opportunities consisted of a mixture of below grade, single and double,
corrugated metal pipe and concrete box culverts, as well as concrete bridging structures. For
further details of below grade passages along this section of Hwy 58 see Bremner- Harrison et al.
( 2007). Note that Bremner- Harrison et al. ( 2007) used the term “ crossing structure” to denote
“ existing structures that had been incorporated into the road design for reasons other than
wildlife passages, such as drainage culverts for run- off, and culverts and bridges for the passage
of seasonal waterways.” This report uses the more generic term “ below grade passage” to
describe the same, reserving the term “ wildlife crossing structure” for those structures designed
specifically for wildlife in mind. Drift fencing was present along both the north and south sides
of Hwy 58 from a study conducted on desert tortoises ( Gopherus agassizii; Boarman and Sazaki
1996). This fencing measured 30– 45 cm ( 11.8– 17.7 in) in height and was intended to guide
tortoises to crossing opportunities. The fencing also may have helped guide kit foxes towards the
passages, but it was not of an adequate height to prevent foxes from jumping over and attempting
to cross the highway at grade.
3.1.2. Methods
3.1.2.1. Trapping
The initial trapping effort to deploy GPS collars on desert kit foxes was conducted during
October– November 2007. Due to unexpected problems with the performance of collars,
including the automated drop- off mechanism ( see below), a second trapping effort was
conducted during March– June 2008 in an attempt to re- trap collared animals and remove the
collars so that the GPS telemetry data stored on the units could be retrieved. The re- trapping
effort was initiated prior to the operational expiration date of the GPS units ( 140 days post-activation).
Trapping transects were established along dirt access roads throughout the study site. Wire mesh
live traps ( 38 x 38 x 107 cm [ 15 x 15 x 42 in] double- door traps; Tomahawk Equipment
Effects of Four- Lane Highways Desert Kit Fox Studies
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Company, Tomahawk, Wisconsin USA) were set along these roads and were no farther than 3
km ( 1.2 mi) from Hwy 58. A single trap was placed on either side of the transect road at intervals
of approximately 0.3 km ( 0.2 mi) in areas that provided sufficient vegetative cover to hide the
trap from view. Each trap was covered with a dark green tarpaulin to make them less
conspicuous, provide shelter from the elements, and to simulate den conditions for captured
animals. Bait consisted of a mixture of hotdogs, boiled eggs and canned cat food. Traps were set
approximately one hour before sunset and checked at sunrise the following morning.
Capture and handling methods for kit foxes were approved by the California State University–
Stanislaus Animal Welfare Committee and the Montana State University Institutional Animal
Care and Use Committee. Methods were consistent with protocols established in a research
permit ( TE825573- 2) from the United States Fish and Wildlife Service and a Memorandum of
Understanding from the California Department of Fish and Game. Captured foxes were coaxed
into a denim handling bag and were physically restrained without chemicals. Foxes were marked
with a uniquely numbered metal ear tag, weighed, sexed, aged, and inspected for overall
condition and injuries. Captured foxes were fitted with GPS/ UHF collars from Televilt. A
description of these collars and their functions were provided previously ( Section 2.1.2.2).
3.1.2.2. Diurnal UHF tracking
Once collar deployment had begun, the study site was visited once per week, during the
designated activity period of the UHF transmitter ( 1000– 1300 hours) in an attempt to track
collared foxes to diurnal den sites. A vehicle- mounted D- 1 omni- directional antenna and a hand-held
directional RX- Pro tracking receiver ( Televilt, Sweden) were used for this purpose.
3.1.2.3. Camera stations
Additional steps were taken to detect further kit fox activity in the area and determine if foxes
retained their collars after the programmed drop- off date. Four motion- activated camera stations
( Cuddeback 3.0 mega pixel scouting cameras) were deployed at four locations within the study
site. Cameras were mounted on 1 m ( 1 yd) steel utility fence posts, which were securely driven
into the ground with a mallet. Bait consisted of Scented Predator Survey Disks ( USDA Pocatello
Supply Depot, Pocatello, Idaho USA) that were placed approximately 3– 4 m ( 3.2– 4.3 yd) in
front of the camera ( one disk per camera). Each camera was set to activate between 1700 hrs and
0600 hrs.
3.1.3. Results
3.1.3.1. Trapping
Between 30 October and 28 November 2007, five individual desert kit foxes were captured ( one
female and four males) and fitted with GPS collars at the Mojave Desert field site ( Figure 20 and
Figure 21). One fox ( Male 6503), initially trapped on the south side of Hwy 58 on 30 October
2007, was recaptured on the north side of the highway on 15 November 2007 ( Figure 20), thus
providing initial evidence of successful crossing of Hwy 58.
Effects of Four- Lane Highways Desert Kit Fox Studies
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Figure 20. Kit fox capture and den locations at the Hwy 58 study site, California.
Figure 21. Desert kit fox with a GPS collar at the Hwy 58 study site, California.
Recovery trapping efforts initially focused on areas where kit foxes had been previously trapped
and tracked to diurnal dens. However, due to a lack of success, the trapping effort was extended
Effects of Four- Lane Highways Desert Kit Fox Studies
Western Transportation Institute Page 37
considerably beyond this area. No foxes were captured during this trapping effort and no GPS
collars were recovered.
3.1.3.2. UHF tracking
Sub- optimal performance of the UHF transmitter component of the GPS collars resulted in
diurnal denning location fixes for only one individual on one occasion. This fox ( Male 6508),
was initially captured on the north side of Hwy 58 on 11 November 2007 and was located on the
south side of the highway on 21 January 2008 ( Figure 20). Fox 6508 was tracked to a
subterranean den situated in the north- facing bank of a man- made excavation. The UHF signal
was very weak. The den containing the fox was detected from a distance of 10.5 m ( 11.5 yd), and
the signal could not be heard beyond a distance of 22 m ( 24 yd) from the den. Telemetry tracking
was discontinued in April 2008 due to the expiration of the UHF transmitter batteries.
3.1.3.3. Camera stations
Camera stations were deployed between 16 April and 9 May 2008 at four locations. These sites
were situated in areas where the majority of foxes were initially captured and therefore in theory
presented the optimal chance for detecting fox activity. Additionally, two of the cameras were
situated close to kit fox dens and two were situated close to kit fox latrines. Images of black-tailed
jackrabbits ( Lepus californicus) visiting the stations were recorded by three of four
cameras during the programmed activity time, indicating that the cameras were functioning
properly. However, no kit fox activity was recorded by any of the cameras at any time.
3.1.4. Discussion
The GPS collars that were employed in this study did not perform as expected and this
significantly inhibited our ability to collect data on movements of telemetered foxes. The UHF
transmitters on the collars proved to be very weak. Despite extensive efforts to monitor collared
foxes, on only one occasion was a signal detected, and this detection likely was a result of the
collared fox being in a den immediately adjacent to the road upon which the monitoring vehicle
was traveling. Subsequent tests revealed that the signal range was only about 20 m ( 22 yd),
which means that the probability of detecting signals from collared foxes was extremely low.
Consequently, virtually no information on fox movements was obtained via monitoring. Also,
the collars were designed with an automated detachment mechanism. Ideally, the collars would
have dropped off the foxes a few weeks prior to the expiration of the UHF transmitter battery so
that the collars could be located. However, it is unclear whether the detachment system failed, or
whether the collars did indeed drop off but could not be located due to the very weak UHF
signals.
Reasons for the inability to re- trap any foxes remain uncertain. The relative ease with which
foxes were trapped during the October/ November 2007 trapping effort might suggest an element
of seasonality in the occurrence of kit foxes in this area. In particular, our efforts to re- trap foxes
were conducted during the early pup- rearing period when foxes may have been remaining close
to natal dens and therefore less likely to encounter our traps. Evidence of kit fox denning activity
was apparent and kit fox tracks and latrines were noted across the study site, indicating that foxes
were still present in the area. However, it is unknown whether the collared animals were still
present.
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Despite the small number of foxes collared, the difficulty in tracking foxes, and the inability to
retrieve GPS data, we still were able to establish that on two separate occasions, two collared
foxes ( 6503 and 6508) did successfully cross Hwy 58. However, no inferences can be made as to
the mode of these crossings ( i. e., through below grade passages or simply over the highway) or
the rate of successful crossings. Bremner- Harrison et al. ( 2007) found no indication that kit foxes
utilized below- grade passages in this area. They did discover two road- killed foxes, including
one at this same study site. This provided evidence that in the absence of median barriers and
exclusionary fencing, kit foxes do occasionally attempt to cross over the surface of the highway.
The successful crossings documented in the current study suggest that four- lane divided
highways lacking exclusionary fencing and median barriers are not absolute barriers to kit fox
movements.
3.2. Second field season ( June to July 2009), California
3.2.1. Study area
The study area used during the second field season was the same as that used in the first season.
See 3.1.1 above for a detailed description of the study area.
3.2.2. Methods
For the second field season, the plan was to capture kit foxes and deploy VHF radio collars on
them. VHF transmitter technology is considered “ conventional” and therefore more reliable than
the much newer and relatively untested GPS collar technology. Radio collars were obtained from
Advanced Telemetry Systems. Descriptions of these collars and their functions were provided
previously ( 2.1.2.1).
Trapping efforts were identical to those described previously. See 3.1.2.1 above for a detailed
description of trapping methods.
3.2.3. Results
Trapping efforts were conducted on seven nights during 11 June– 30 July 2009. However, only
two foxes were captured and collared ( one female and one male). Both foxes were captured on
the south side of Hwy 58. On the final night of trapping in July, the male was recaptured, again
on the south side of Hwy 58, and the decision was made to remove his collar.
During July 2009, the female fox was relocated five times in three different dens. All of these
dens were located on the south side of Hwy 58.
3.2.4. Discussion
For unknown reasons, kit fox capture rates on the study site were lower than expected. The
region had experienced several consecutive years of below- average precipitation, and other
biologists working in the region reported that prey abundance ( e. g., nocturnal rodents, rabbits)
might be depressed. Two foxes were not likely to provide meaningful data, nor warrant the time
and expense that would have been required to monitor these animals. Therefore, the decision was
made to terminate the effort in California and redirect resources elsewhere.
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Trapping and monitoring efforts provided only limited information on kit fox movements, due to
the low number of collared foxes. The information collected did not provide any evidence that
foxes had crossed Hwy 58.
Effects of Four- Lane Highways Conclusions
Western Transportation Institute Page 40
4. CONCLUSIONS
4.1. Colorado swift fox study
1. Based on data obtained from one retrieved GPS collar, I- 70 appeared to act as a barrier
for at least one adult female swift fox during an 88- day period. Available habitat might
explain why this individual had no reason to cross.
2. One unmarked swift fox was seen crossing I- 70 at grade and swift fox tracks crossing at
grade in snow illustrate a swift fox attempt to cross this four- lane highway. For
clarification, these successful crossings took place where no solid median barriers exist
since most of the length of I- 70 is divided only by a grassy median.
3. At least two swift foxes appeared to cross I- 70 through two reinforced concrete pipe
culverts in the study area; the two culverts are located ~ 27 km ( 17 mi) apart.
4. During the study period, swift fox tracks were detected in track beds at one end of a
number of the below- grade passages on several occasions. Red fox and coyote tracks
were also detected in and around culvert entrances with some indicating complete
crossings. Swift fox crossings were detected in culverts where red fox and coyote
crossings were not detected. Studies have shown that culverts can be prey traps in some
areas ( Doncaster 1999; Hunt et al. 1987).
5. The presence of prey may have attracted some swift foxes to some of the culverts.
6. The failure of the GPS- UHF technology used in this project severely limited our ability to
study swift fox movements in relation to I- 70.
4.2. South Dakota swift fox study
1. Based on VHF telemetry data and visual observation, I- 90 does not act as a barrier to at-grade
crossings. All eight tracked swift foxes were found on opposite sides of I- 90
multiple times throughout the study.
2. Rainy weather and subsequent flooding/ washouts made consistent culvert monitoring
impossible. Still, swift fox use and/ or crossings were documented in several different
culverts.
3. There is evidence that swift foxes crossed I- 90 through at least four two- lane, one four-lane
and possibly a six- lane culvert. The four- lane crossing was through a box culvert.
The six- lane crossing is not confirmed because the animal may have accessed the culvert
via an open grate in the median.
4. Two swift foxes ( adult– pup pair) made complete four- lane crossings via a two- lane
culvert pair opening into the median when fencing was present. The same culvert system
had no documented swift fox use prior to fencing. This may be explained by the
geographic location of different active dens during the pre- and post- fencing study
period. It may also indicate that fencing can be useful in funneling foxes to culverts.
5. The culverts that had documented swift fox crossings were relatively short in length ( i. e.,
typically spanning two versus four lanes).
Effects of Four- Lane Highways Conclusions
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6. In the case of the single documented four- lane crossing, the culvert was relatively tall and
wide ( i. e., a 213 x 213 cm ( 84 x 84 in) box culvert) compared to the more readily
available pipe culverts. Approximately 80% ( n = 43) of the pipe culverts monitored
measured 91 x 91 cm ( 36 x 36 in) or less
7. Of the swift foxes killed by traffic, pups are the most common.
4.3. California desert kit fox study
1. Two collared kit foxes were documented to have successfully crossed Hwy 58 on a study
site in California. It is unknown whether the foxes crossed the road at grade or used
below grade passages. No exclusionary fencing or median barrier is present along this
stretch of Hwy 58.
2. The failure of the telemetry technology used in this project was disappointing and
significantly inhibited our ability to achieve study objectives.
3. Use of below grade passages by foxes was not addressed during this investigation. Such
passages were monitored during a previous investigation, but no use by kit foxes was
detected ( Bremner- Harrison et al. 2007). However, in another study conducted to
examine use of below grade passages by desert tortoises on the Hwy 58 study site, kit
foxes were detected using culverts with the following dimensions: 0.9– 1.5 m ( 1– 1.6 yd)
diameter steel pipe; 1.4- m ( 1.5- yd) diameter concrete pipe; and concrete boxes 3– 3.6 m
( 3.3– 4 yd) wide by 1.8– 3 m ( 2– 3.3 yd) high ( Boarman and Sazaki 1996).
Effects of Four- Lane Highways Recommendations
Western Transportation Institute Page 42
5. RECOMMENDATIONS
Because we had limited data on San Joaquin kit fox use of below grade passages ( i. e., culverts or
bridge undercrossings) along four- lane highways ( Bremner- Harrison et al. 2007), we used
surrogate species to increase our data collection potential. In this report, we consider data
collected on swift fox and desert kit fox ( hereafter referred to as foxes, unless otherwise
specified) to be valid for making mitigation recommendations for San Joaquin kit foxes
throughout their range in California. The reasons that swift fox and desert kit fox data are
applicable to San Joaquin kit fox mitigation are detailed in our literature review report to
Caltrans ( Clevenger and Kociolek 2007).
Swift fox were studied along Interstate 70 near Limon in eastern Colorado and along Interstate
90 near Wall in southwestern South Dakota. Desert kit fox were studied along California State
Highway 58 near Barstow in southern California. The aim of these companion studies was to
investigate the movements and highway crossing behavior of swift and desert kit foxes around
four- lane highways to make inferences for San Joaquin kit foxes.
The four- lane highways in our study areas were generally not a barrier to movement of swift fox
and desert kit fox. Thus, we can assert the same highway- crossing relationship is true in most
cases for San Joaquin kit fox. As a baseline, the South Dakota site had an average daily traffic
( ADT) of up to 6,000 vehicles in 2008, and the Colorado and California sites had relatively
comparable ADT volumes of approximately 11,500 vehicles in 2006 and 2007. Mortality of
foxes does occur throughout the year, primarily after pups are reared and young begin to travel
more and disperse from natal ranges ( Cypher et al. 2009). Rates of mortality vary from study
area to study area, and in most instances appear to be sustainable for local populations of foxes.
However, for the precarious San Joaquin kit fox population road- related mortality may exert a
strong influence on the ability of local populations to persist over time. Particularly given the fact
that traffic volumes will be increasing on highways in San Joaquin kit fox range and the risk of
mortality while crossing these highways will increase from current conditions.
San Joaquin kit foxes exist in a demographically vulnerable metapopulation. Metapopulations
are patchily distributed networks of localized sub- populations. In most cases, individual
subpopulations cannot survive on their own and are subject to extirpation or “ winking out.”
Maintenance of sub- populations depends on the movement of individuals from “ source”
populations through the metapopulation network ( Hanski 1999).
Within the San Joaquin kit fox metapopulation, six areas are considered to contain important kit
fox populations ( US Fish and Wildlife Service 1998). Three populations have been designated a
high priority for enhancement and protection and are considered “ source populations” for the
larger San Joaquin kit fox metapopulation ( Haight et al. 2002). Sustainable rates of road- related
mortality will likely occur in the source populations of San Joaquin kit fox range, i. e., areas
characterized by relatively high fox densities, productivity and dispersal potential. However, in
non- source or marginal populations, characterized by low population density, low or variable
reproduction and limited dispersal, road- related mortality could have serious negative
consequences for the persistence of non- source populations, thus pose a significant risk to the
long- term viability and stability of the metapopulation.
Effects of Four- Lane Highways Recommendations
Western Transportation Institute Page 43
We provide recommendations with regard to highway mitigation practices in San Joaquin kit fox
range with the goal of maintaining and restoring demographic and genetic connectivity within
the metapopulation. These recommendations reflect conclusions in Chapter 4 of this report.
5.1. Connectivity zones
Movement and dispersal ( hereafter referred to as movement) among source and non- source
populations in the metapopulation will likely occur through three possible connectivity zones: ( 1)
between two source populations, ( 2) between source and non- source populations or ( 3) between
two non- source populations ( Figure 22). It will be important for San Joaquin kit fox management
to be able to identify where movement is likely to occur, what influences movement and gene
interchange, and how transportation infrastructure may affect movement and the exchange of
individuals and genes.
Figure 22. Conceptual movement patterns of individuals among populations within the San Joaquin kit fox
metapopulation. Blue dots are source populations. White dots are non- source populations. Roads are solid
black lines. Three possible connectivity zones show movement between source populations ( blue dashed line),
between source and non- source populations ( green dashed line) and between non- source populations ( red
dashed line). This simple conceptual model shown assumes movement is typically between nearest
populations.
Research – The following outlines steps required to help management in the planning, design
and implementation of mitigation measures along Caltrans infrastructure within San Joaquin kit
fox range. A critical first step in planning and designing measures for San Joaquin kit fox
consists of identifying broad and fine- scale movement corridors ( connectivity zones) within the
metapopulation. These movement corridors can be identified from analysis of gene flow using
genetic data previously collected for research on gene flow in the metapopulation ( Schwartz et
al. 2005). We recommend a multimodal landscape resistance approach be used and tested with
available genetic data to help robustly delineate corridors for movement and gene flow within the
metapopulation ( Cushman et al. 2006). This approach models gene flow by evaluating the
influence of landscape and environmental factors in the San Joaquin kit fox range.
With connectivity zones delineated and mapped, the second step requires identifying roads and
other transportation infrastructure that bisect the three types of connectivity zones ( Figure 22).
Effects of Four- Lane Highways Recommendations
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Once these “ conflict areas” between roads and connectivity zones are identified, short- term and
long- term mitigation plans can be developed to maintain and restore kit fox movement within the
metapopulation.
The third and final step consists of developing solutions and plans for mitigating the conflict
zones in the short and long term. Short- term mitigation options may consist of ( 1) removing
existing solid median barriers ( e. g., Jersey barriers) or ( 2) retrofitting existing below- grade
passages ( e. g., culverts, bridge undercrossings) as safe highway crossing structures for kit foxes
and other wildlife. Long- term solutions generally will be part of highway expansion projects in
San Joaquin kit fox range. Mitigation measures such as wildlife underpasses and overpasses
could potentially be constructed to maintain and restore connectivity within the metapopulation;
the latter if part of mitigation for pronghorn movement in the San Joaquin Valley. Although not
part of Caltrans facilities, identifying conflict zones between kit fox movement and irrigation
canals will be useful for making recommendations to irrigation districts to reduce their impact on
movement and gene flow. Bridges over canals have been successfully used to mitigate
movement of large and small mammals in Canada and Europe ( A. Clevenger, pers. obs.).
Mitigation plans will be different among the three connectivity zones as the urgency of
conservation efforts in each varies and depending on whether they intersect existing roads,
planned road expansions ( two- to four- lanes) and corresponding traffic volumes. We discuss
short- term solutions for existing roads and long- term solutions for roads that eventually will be
upgraded with additional lanes of traffic in Table 9. The recommendations encompass the types
of mitigation discussed below.
Effects of Four- Lane Highways Recommendations
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Table 9. Short- term solutions for existing roads and long- term solutions for roads that eventually will be upgraded with additional lanes of traffic.
Existing ( short term) Existing ( short term) Expansion ( long term)
Connectivity zone Low volume High volume High volume
Source –
Source
Median barriers – Do not install. Replace with
alternative designs that are more permeable for kit fox
movement. Highly recommended.
Below- grade passages – Retrofit to enhance kit fox
movement. Not recommended.
Fencing – Can be used on bridge or culvert retrofits
to enhance kit fox movement. Not recommended.
Median barriers – Do not install. Replace with
alternative designs that are more permeable for kit fox
movement. Highly recommended.
Below- grade passages - Retrofit to enhance kit fox
movement. Recommended.
Fencing – Can be used on bridge or culvert retrofits to
enhance kit fox movement. Not recommended.
Median barriers – Do not install. Replace with
alternative designs that are more permeable for kit fox
movement. Highly recommended.
Below- grade passages and/ or wildlife crossing
structures - Retrofit and/ or build to enhance kit fox
movement. Recommended.
Fencing – Can be used on bridge or culvert retrofits to
enhance kit fox movement. Recommended.
Source –
Non- source
Median barriers – Do not install. Replace with
alternative designs that are more permeable for kit fox
movement. Highly recommended.
Below- grade passages – Retrofit to enhance kit fox
movement. Recommended.
Fencing – Can be used on bridge or culvert retrofits
to enhance kit fox movement. Not recommended.
Median barriers – Do not install. Replace with
alternative designs that are more permeable for kit fox
movement. Highly recommended.
Below- grade passages - Retrofit to enhance kit fox
movement. Recommended.
Fencing – Can be used on bridge or culvert retrofits to
enhance kit fox movement. Not recommended.
Median barriers – Do not install. Replace with alternative
designs that are more permeable for kit fox movement.
Highly recommended.
Below- grade passages and/ or wildlife crossing
structures – Retrofit and/ or build to enhance kit fox
movement. Highly recommended.
Fencing – Can be used on bridge or culvert retrofits to
enhance kit fox movement. Recommended.
Non- source -
Non- source
Median barriers – Do not install. Replace with
alternative designs that are more permeable for kit fox
movement. Highly recommended.
Below- grade passages - Retrofit to enhance kit fox
movement. – Recommended.
Fencing – Can be used on bridge or culvert retrofits
to enhance kit fox movement. Not recommended.
Median barriers – Do not install. Replace with
alternative designs that are more permeable for kit fox
movement. Highly recommended.
Below- grade passages – Retrofit to enhance kit fox
movement. Highly recommended.
Fencing – Can be used on bridge or culvert retrofits to
enhance kit fox movement. Recommended.
Median barriers – Do not install. Replace with
alternative designs that are more permeable for kit fox
movement. Highly recommended.
Below- grade passages and/ or wildlife crossing
structures – Retrofit and/ or build to enhance kit fox
movement. Highly recommended.
Fencing – Can be used on bridge or culvert retrofits to
enhance kit fox movement. Recommended.
Effects of Four- Lane Highways Recommendations
Western Transportation Institute Page 46
5.2. Median barriers
Highway median barriers are used to divide opposing lanes of traffic flow and reduce the risk of
cross median collisions. Clevenger and Kociolek ( 2006) synthesized a state of the practice with
regard to median barriers for Caltrans. The following are excerpts from that report ( Clevenger
and Kociolek 2006):
1. The relative number of cross median accidents is low when compared to total accidents,
but the proportion of associated fatalities and injuries is substantially higher ( FHWA
2006a, Macedo 1999, Lynch et al. 1993).
2. The Federal Highway Administration has accepted as crashworthy a variety of concrete,
metal beam, cable and other median barrier designs that have passed National
Cooperative Highway Research Program ( NCHRP) 350 Tests ( FHWA 2006a and b).
3. The US Department of Transportation ( USDOT) has stated the need for an alternative to
traditional concrete and metal beam barriers because they can be expensive and difficult
to install, citing a nationwide goal for each state to identify appropriate projects for
deploying cable median barriers as a potential solution ( USDOT 2006).
4. FHWA names cable barriers and rumble strips as two priority technologies with proven
benefits and which are ready for deployment ( Taylor 2005).
Solid median barriers have the potential to obstruct at- grade movement of San Joaquin kit foxes
across highways and can increase the time they are on highways and thus the risk of road- related
mortality. Clevenger and Kociolek ( 2006) assessed potential permeability and mortality risks
associated with median barriers for small-, mid-, and large- bodied taxa. Mid- sized animals,
including fox, had some of the highest combined risk scores for a variety of concrete median
barrier types given that foxes are likely to be too big to utilize scuppers and may be too small to
easily jump over barriers ( Clevenger and Kociolek 2006).
As indicated above, solid median barriers should not be constructed on any highways or highway
upgrade projects in San Joaquin kit fox range, particularly where any connectivity zones exists,
even between source populations ( Table 9). Where solid median barriers are found on existing
sections of highway within the connectivity zones efforts need to be made to remove solid
median barriers and replaced with the alternative barrier types listed below. If no solid median
barriers are present along highways in connectivity zones, they should remain free of solid
median barriers. Alternative median barrier designs should be incorporated into all new highway
designs and retrofitting sections with solid median barriers in connectivity zones. Cable, box
beam and even thrie- beam barriers will allow for greater cross- highway movement by foxes and
pose less of a mortality risk for foxes choosing to cross at- grade.
Research – Additional research is needed to better understand the effects of highway median
barriers of all types on movements and mortality risks of San Joaquin kit foxes.
5.3. Below and above grade passage design and planning
To ensure performance and function, below and above grade passages ( i. e., drainage culverts and
wildlife crossing structures built either below or above grade) should be situated in connectivity
zones that serve to link populations. Information on San Joaquin kit fox occurrence, distribution
and landscape connectivity will be essential for planning the location of culverts and crossing
Effects of Four- Lane Highways Recommendations
Western Transportation Institute Page 47
structures along highways in the San Joaquin kit fox metapopulation ( see 5.1 Connectivity Zones
above).
On existing highways with low traffic volumes ( i. e., two lanes), retrofitting culverts and crossing
structures is recommended in connectivity zones linking source and non- source populations and
between non- source populations ( Table 9). Retrofits are not recommended in connectivity zones
linking source populations because even accounting for road- related mortality the source
populations should be able to thrive. On existing highways with high traffic volumes ( i. e., four
lanes), efforts should be made to retrofit culverts and crossing structures to improve movements
across highways and allow for exchange of individuals and genes between populations. When
highway expansion projects occur within the metapopulation, a variety of culverts, underpasses,
and overpasses are highly recommended in connectivity zones linking source and non- source
populations and between non- source populations. However, in connectivity zones linking source
populations crossing structures are recommended but less critical for kit fox conservation.
Culverts and crossing structures should be designed to conform to local topography. Drainage
features should be included in crossing structures to minimize flooding within the structures.
Culverts will inevitably have some standing or running water through them seasonally.
Typically, more culverts and crossing structures provide greater highway permeability for foxes.
The best practice would be to install as many culverts and/ or crossing structures as possible
within the San Joaquin kit fox metapopulation or range. Given the average home range size of
San Joaquin kit foxes ( 5.9 km2 with 2.7 km diameter; Nelson et al. 2007), we recommend a
minimum of one culvert or crossing structure every 0.5 km ( 0.3 mi). This would result in
multiple opportunities for safe below or above grade crossings in each fox home range.
The smallest diameter culvert used by swift fox to cross a highway in this study was 46 cm ( 18
in); however, it only facilitated a two- lane crossing. The only documented four- lane crossing was
through a box culvert measuring 213 x 213 cm ( 84 x 84 in). We were unable to obtain sufficient
data at the monitored culverts to make strong inferences regarding the design of culverts for San
Joaquin kit foxes. Nonetheless, some general principles with regard to design of wildlife
crossings can be used as guidelines for this species ( Clevenger and Huijser 2009).
Culverts should be variable in size but a minimum diameter of 61 cm ( 24 in). In larger culverts
and underpasses, escape dens should be constructed ( see below).
Research – Within five years, if additional culverts and crossing structures are built on highways
within the San Joaquin kit fox range, additional research should be carried out to better
understand the relationship between fox movement, gene flow, mortality and crossing structure
design. In the meantime, cameras may be installed to monitor existing culverts and crossing
structures.
5.4. Fencing
The short amount of time we were able to test the effectiveness of fences to increase fox use of
culverts provided interesting results. In the absence of median barriers, however, our broader
results suggest that fencing is not necessary in most instances. On two- lane highways fencing
will not be necessary as the risk of mortality is low. The same is true on four- lane highways in
connectivity zones linking source populations and source and non- source populations as
incidence of mortality will most likely have a negligible effect on the population ( Table 9). In
Effects of Four- Lane Highways Recommendations
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areas linking non- source populations, however, fencing to funnel movement to existing crossing
structures is recommended.
Research – There is a need for more tests evaluating whether fencing will facilitate use of below
grade passages by foxes. The temporary chicken- wire fencing used in this experiment was
relatively inexpensive. The cost to install 5.5 km ( 3.4 mi) of fencing and encompassing two
culverts was approximately $ 12,000. While permanent fencing would likely cost more, it would
be a fraction of the cost of installing a culvert or crossing structure. Fencing may be a low- cost
solution to improve below or above grade passage use by San Joaquin kit foxes and reduce road-related
mortality. Additional studies should be conducted within San Joaquin kit fox range as to
the efficacy of fencing on fox use of below or above grade passages.
5.5. Prey traps
Given the fact that competitor species ( e. g., coyotes, red foxes) also were detected near and in
below grade passages, mitigation should include escape dens within crossing structures. This
consists of a 3- m ( 10- ft) length of 20- cm ( 8- in) diameter pipe anchored in the structure ( with the
entrance constricted to 10– 15 cm [ 4– 6 in] to exclude red foxes). This is becoming a common
mitigation design for culverts and underpasses within the San Joaquin kit fox range.
Alternatively, grating could be placed over the entrance of the structures that would allow kit
foxes to pass, but not larger predators. This can only be implemented in areas where local
hydrology does not allow trash and vegetation to collect on the grate and cause flooding.
5.6. GPS technology
GPS technology may still be useful for an investigation of this nature, however, not until the
deficiencies we encountered are corrected. Other methodologies that could be employed to
achieve study objectives include VHF telemetry and genetic analyses of fecal or hair samples
collected from study sites.
5.7. Species occurrence surveys
Critical to effective and proactive planning of mitigation for San Joaquin kit foxes will be
science- based information about current population status, distribution, and demographic trends.
This information can be obtained from species occurrence surveys within the metapopulation
with an eye on where transportation projects may impact connectivity zones, local populations
and their long- term persistence. We recommend that Caltrans, in conjunction with California
Fish and Game and the U. S. Fish and Wildlife Service, establish a long- term, population and
genetic monitoring program for San Joaquin kit fox metapopulation. Once established, the
monitoring program will track changes in the genetic variability and gene flow of kit fox in the
San Joaquin Valley. With the recent development of non- invasive genetic sampling techniques
( Smith et al. 2001, Bremner- Harrison et al. 2006) these monitoring efforts can be conducted
without the major expenses of trapping studies and will provide important data on changes in kit
fox genetics and demography. These types of efforts will also help detect unknown populations,
if they exist, or at least help quantify individual foxes that may reside, and possibly breed, in the
spaces between known populations. The data will provide current information on that status of
the metapopulation, between population movement, help identify areas where highway- related
mortality may have population- level impacts, and help retrofit existing infrastructure or design
new mitigation measures ( e. g., crossing structures) to increase highway permeability and reduce
Effects of Four- Lane Highways Recommendations
Western Transportation Institute Page 49
mortality. This will also make possible a more effective and proactive planning of highway
mitigation actions on future highway expansion projects in San Joaquin kit fox range.
Effects of Four- Lane Highways References
Western Transportation Institute Page 50
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synthesis of existing data. Pages 397- 406 in C. L. Irwin, P. Garrett and K. P. McDermott,
( eds.) 2003 Proceedings of the International Conference on Ecology and Transportation.
Center for Transportation and the Environment, North Carolina State University, Raleigh,
N. C.
Boarman, W. I., and Sazaki, M. 1996. Highway mortality in desert tortoises and small vertebrates:
success of barrier fences and culverts. Pages 169- 173 in G. L. Evink, D. Zeigler, P. Garrett
and J. Berry ( eds.). Highways and movement of wildlife: improving habitat connections
and wildlife passageways across highway corridors. Florida Department of Transportation,
Tallahassee, Florida, USA.
Boarman, W. I., and M. Sazaki. 2006. A highway’s road- effect zone for desert tortoises
( Gopherus agassizii). Journal of Arid Environments 65: 94- 101.
Bremner- Harrison, S., B. Cypher, C. Fiehler, A. P. Clevenger and D. Hacker. September 2007.
Use of highway crossing structures by San Joaquin kit foxes: Final report to California
Department of Transportation in fulfillment of Contract No. 43A068, Memorandum of
Understanding No. 68.
Caltrans Highway Design Manual, The. 2009. http:// www. dot. ca. gov/ hq/ oppd/ hdm/ hdmtoc. htm
[ Accessed 15 March 2010].
Clevenger, A. P. 2005. Design and performance of wildlife crossings for kit foxes and
ecologically similar small carnivores: A literature review and semi- annotated
bibliography. Prepared for California Department of Transportation, San Luis Obispo,
California.
Clevenger, A. P. and M. P. Huijser. 2009. Handbook for design and evaluation of wildlife
crossing structures in North America. Report prepared for the Federal Highway
Administration.
Clevenger, A. P. and A. V. Kociolek. 2006. Highway median impacts on wildlife movement and
mortality: State of the practice and gaps analysis. Report prepared for California
Department of Transportation in partial fulfillment of Contract No. 65A0219.
Clevenger, A. P. and A. V. Kociolek. 2007. Transportation effects on swift fox ( Vulpes velox)
and study site selection. Report prepared for California Department of Transportation in
partial fulfillment of Contract No. 65A0250.
Colorado Department of Transportation. 2009.
http:// www. dot. state. co. us/ App_ DTD_ DataAccess/ Traffic/ index. cfm? fuseaction= Traffic
Main& MenuType= Traffic [ Accessed 8 February 2010].
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Testing multiple hypotheses with causal modeling. American Naturalist 168: 486- 499.
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Cypher, B. L., C. D. Bjurlin, and J. L. Nelson. 2009. Effects of roads on endangered San Joaquin
kit foxes. Journal of Wildlife Management 73( 6): 885- 893.
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Forman, R. T. T. and L. E. Alexander. 1998. Roads and their major ecological effects. Annual
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J. White, and D. Williams. 2002. Optimizing habitat protection using demographic
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Hanski, I. 1999. Metapopulation ecology. Oxford University Press, Oxford, U. K.
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( eds.), The swift fox: Ecology and conservation in a changing world. Canadian Plains
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effects of roads, pp. 98– 116. The National Academies Press.
Nelson, J. L., B. L. Cypher, C. D. Bjurlin and S. Creel. 2007. Effects of habitat on competition
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surrounding area in South Dakota. Master’s Thesis. South Dakota State University,
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Effects of Four- Lane Highways Appendix
Western Transportation Institute Page 53
7. APPENDIX A
7.1. 2009– 2010 South Dakota culvert monitoring scheme and swift fox
detections
Subsection Culvert code Monitoring tool Monitoring period ( month/ day) Swift fox detected
I
B117A camera; too flooded for track bed 8/ 28- 9/ 3; 9/ 28- 10/ 5 no
R117B track bed 6/ 25- 10/ 30; mostly inoperable no
R117C track bed 6/ 25- 10/ 30; mostly inoperable no
R117D track bed 6/ 25- 10/ 30; mostly inoperable no
R118C track bed 6/ 25- 10/ 30; mostly inoperable yes
R119A track bed 6/ 25- 10/ 30; mostly inoperable no
R119B
track bed 6/ 25- 10/ 30; mostly inoperable yes
camera 9/ 2- 9/ 14 yes
R119C
track bed 6/ 25- 10/ 30; mostly inoperable yes
camera 9/ 3- 9/ 14; 9/ 16- 9/ 22 yes
R119D camera; too flooded for track bed 9/ 28- 10/ 5 no
R119E
track bed 6/ 25- 10/ 30; mostly inoperable no
camera 10/ 7- 10/ 14 no
R120A track bed 6/ 25- 10/ 30; mostly inoperable yes
B120B track bed 6/ 25- 10/ 30; mostly inoperable no
R120B track bed 6/ 25- 10/ 30; mostly inoperable no
R120C track bed 6/ 25- 10/ 30; mostly inoperable no
R121A
track bed 6/ 25- 10/ 30; mostly inoperable no
camera 9/ 28- 10/ 5 no
R121C
track bed 6/ 25- 10/ 30; mostly inoperable no
camera 7/ 13- 10/ 6; 10/ 15- 11/ 19 yes
R121D
track bed 6/ 25- 10/ 30; mostly inoperable yes
camera 10/ 7- 10/ 14 no
R121E track bed 6/ 25- 10/ 30; mostly inoperable no
R122A track bed 6/ 25- 10/ 30; mostly inoperable no
R122B track bed 6/ 25- 10/ 30; mostly inoperable no
R122D track bed 6/ 25- 10/ 30; mostly inoperable no
II
B126A
track bed 6/ 25- 10/ 30; mostly inoperable no
camera 7/ 2- 10/ 6; 10/ 15- 11/ 19 yes
R126B track bed 6/ 25- 10/ 30; somewhat inoperable no
R127A track bed 6/ 2