Management and Conservation Article
Changes in Kit Fox Defecation Patterns
During the Reproductive Season:
Implications for Noninvasive Surveys
KATHERINE RALLS,1 Center for Conservation and Evolutionary Genetics, Smithsonian Conservation Biology Institute, National Zoological Park,
Washington, D.C. 20008, USA
SANDEEP SHARMA, Center for Conservation and Evolutionary Genetics, Smithsonian Conservation Biology Institute, National Zoological Park,
Washington, D.C. 20008, USA
DEBORAH A. SMITH, Working Dogs for Conservation, 52 Eustis Road, Three Forks, MT 59752, USA
SAMANTHA BREMNER-HARRISON, California State University, Stanislaus, Endangered Species Recovery Program, P.O. Box 9622, Bakersfield,
CA 93389, USA
BRIAN L. CYPHER, California State University, Stanislaus, Endangered Species Recovery Program, P.O. Box 9622, Bakersfield, CA 93389, USA
JESU?S E. MALDONADO, Center for Conservation and Evolutionary Genetics, Smithsonian Conservation Biology Institute, National Zoological Park,
Washington, D.C. 20008, USA
ABSTRACT Noninvasive survey methods based on analyzing DNA extracted from feces can be useful for carnivores that are difficult to
study by other methods. Changes in fecal deposition patterns associated with reproduction in kit foxes (Vulpes macrotis) might affect results of
such surveys. We used a trained dog to collect fresh scats on 2-km transects in the home ranges of 11 radiocollared female kit foxes in January,
February, and March 2008 and determined sex of the individual that deposited the scats by amplifying the zinc finger protein gene. Female
foxes give birth in mid-February to mid-March. We found a similar number of scats each month. In January, the sex ratio of the scats was not
different from the expected 1:1. However, in February there were almost 2 male scats for every female scat and in March there were .8 male
scats for every female scat. Comparing March to January, there were more male scats on all 11 transects and fewer female scats on 10 of 11
transects. Around the time pups are born, both sexes appear to show changes in fecal deposition patterns that make it easier to find male scats
and harder to find female scats. Effects of these changes on survey results will vary depending on the purpose and design of the survey. Surveys
to determine distribution and relative abundance would probably not be negatively affected by these changes. However, if surveys to estimate
abundance are conducted during the reproductive season, they could result in an underestimate of population size unless the increased
heterogeneity in scat detectability is taken into account.
KEY WORDS capture heterogeneity, feces, kit fox, noninvasive surveys, scat, sex ratio, Vulpes macrotis, zinc finger protein gene.
Many carnivore species are difficult to study by direct
observation or capture?recapture methods. Population
densities may be low, home ranges large, and the animals
nocturnal and secretive. Because of these problems, there is
increasing interest in developing more effective noninvasive
survey methods for carnivores (Long et al. 2008). Nonin-
vasive survey methods include recent approaches based on
isolating and analyzing DNA extracted from hairs or feces
(scats; Schwartz and Monfort 2008). Molecular genetic
analyses of DNA extracted from feces can be used to
document distribution and abundance (Smith et al. 2006a),
determine sex ratios (Smith et al. 2006b), or estimate
population size (Frantz et al. 2003, Bellemain et al. 2005,
Prugh et al. 2005, Ruell et al. 2009, Cubaynes et al. 2010).
Studies of the accuracy of noninvasive surveys based on
fecal DNA have focused on genotyping errors (Taberlet et
al. 1996, Mills et al. 2000, Miller et al. 2002, McKelvey and
Schwartz 2004, Smith et al. 2006b). Differences in fecal
deposition patterns related to age, sex, social, or reproduc-
tive status might also lead to errors in analyses based on fecal
DNA genotypes (Kohn et al. 1999, Cubaynes et al. 2010).
However, for most species little is known about the details
of such differences in fecal deposition patterns or how they
might affect results of noninvasive surveys based on fecal
DNA.
Differences in the number of scats found per kilometer
searched have provided information on distribution and
relative abundance of San Joaquin kit foxes (Vulpes macrotis
mutica; Smith et al. 2006a). Because these surveys must
cover a broad area and funding to survey different areas
becomes available at different times, different areas have
been surveyed at different times of year. The kit fox is a
seasonally breeding species in which females give birth
annually in mid-February to mid-March (Egoscue 1956,
Zoellick et al. 1987). We speculated that scats of females
might become more difficult to find during the pupping
season. If so, surveys at this time of year could give a
misleading impression of kit fox distribution and relative
abundance. To evaluate this hypothesis, we collected kit fox
scats during the last 2 weeks of each month in January,
February, and March 2008 and determined sex of the
individual that deposited the scats by amplifying a short
fragment of the zinc finger protein genes that is a fast and
reliable method of determining sex from feces in kit foxes
(Ortega et al. 2004).
Kit foxes are socially monogamous and mated pairs remain
together throughout the year (Ralls et al. 2007); thus the
expected sex ratio for live animals is 1:1. Numerous field
studies (summarized in Moehrenschlager et al. 2004), as1 E-mail: rallsk@thegrid.net
Journal of Wildlife Management 74(7):1457?1462; 2010; DOI: 10.2193/2009-401
Ralls et al. N Changes in Sex Ratio of Fox Scats 1457
well as molecular sexing of scats collected in July (Smith et
al. 2006b), confirmed this expectation. Thus, we expected to
find approximately equal numbers of male and female scats
each month if the scats of males and females were equally
likely to be found.
STUDY AREA
We conducted fieldwork in the southern San Joaquin
Valley, California, USA, at the Lokern Natural Area.
Lokern was in western Kern County, approximately 40 km
west of Bakersfield (Fig. 1). The Mediterranean climate was
characterized by hot, dry summers and cool, wet winters.
Annual precipitation averaged about 14 cm but was highly
variable (Spiegel 1996). February was the wettest month
during our study; monthly rainfall totals for Bakersfield in
2008 were 1.68 cm in January, 2.08 cm in February, and a
trace in March (National Oceanic and Atmospheric
Administration 2009). Vegetation consisted primarily of
nonnative annual grassland with some areas of arid-land
shrubs. Detailed descriptions of the area are given in Spiegel
(1996) and Nelson et al. (2007).
METHODS
Most pups have dispersed from their natal territories by
January, so the population on the study area consisted
mainly of resident adult pairs. Eleven radiocollared adult
females (Fig. 1) were captured previously as part of a
different study using wire-mesh live traps (model 109;
Tomahawk Equipment Company, Tomahawk, WI) and
fitted with an approximately 40-g very high frequency
(VHF) radiocollar (model 1930; Advanced Telemetry
Systems, Isanti, MN). We were authorized to study San
Joaquin kit foxes under Endangered Species Act permit TE-
825573-3 from the United States Fish and Wildlife Service
and a Memorandum of Understanding with the California
Department of Fish and Game. We followed standard
methods designed to minimize risk of stress or injury
(Cypher et al. 2000), approved by both agencies, for
trapping, handling, and radiocollaring kit foxes. We tracked
each radiocollared female to her den once per week.
Previous studies indicated that trained dogs find more
scats than do human observers (Smith et al. 2003), so we
used a professional detection dog and handler team
(Working Dogs for Conservation, Three Forks, MT) to
search for scats. The dog and handler had extensive
experience collecting kit fox scats. We used only one dog
in our study. In an earlier study in a nearby area (Smith et al.
2003), the mitochondrial DNA extracted from scats found
by this dog indicated that it was consistently accurate at
finding only kit fox scats (and ignoring those of other
species such as coyotes [Canis latrans]) in this area.
To ensure that we collected scats from multiple fox home
ranges, we established a 2-km survey route within an area we
judged to be part of each radiocollared female?s home range
based on locations of dens. We gave the investigator that
established these transects information on the general area
used by each female but not on the locations of her dens.
Most transects were looped or continuous routes to
eliminate backtracking. We included unpaved roads and
vegetated areas as available, because dogs found numerous
scats along both of these substrates in other studies (Smith
et al. 2003). Previous work indicated that dogs found about
25 scats/km in the Lokern area (Smith et al. 2006a), so we
expected to find about 50 scats per transect or 550 scats each
month. Although dogs locate many old scats that contain
DNA that is too degraded for successful polymerase chain
reaction (PCR) amplification of the zinc finger protein
genes used for determining sex (Ortega et al. 2004), we
expected to find about 150 fresh, useable scats per month.
Chi-square simulations indicated that sexing as few as 125
scats per month would give us a high degree of statistical
power to distinguish between a sex ratio of 60 male to 40
female scats and the expected 50:50 ratio.
We conducted scat searches in January, February, and
March 2008 for 6 to 7 days during the last 2 weeks of each
month. When the dog alerted its handler to presence of a kit
fox scat, the location of the scat was geo-referenced with a
Global Positioning System (GPS). We collected and used
for DNA analysis only scats deposited by adult foxes (adult
scats are much larger than scats produced by young pups)
with the physical characteristics of fox scats ,8 days old as
determined by our freshness rating method (see Smith et al.
2003). We stored scats in plastic bags containing 1 teaspoon
of silica gel for desiccation (Fisher Scientific, Pittsburgh,
PA) and shipped samples within 7 days of collection to the
genetics laboratory at the National Zoological Park for
storage at 220u C.
Laboratory Procedures
Shortly after the samples arrived at the genetics laboratory,
we extracted DNA from every scat sample using the
QIAGEN DNeasyTM extraction kit (Qiagen Inc., Valencia,
CA) and following the modified protocols outlined in
Eggert et al. (2005). We conducted DNA extractions in a
separate facility away from the genetics laboratory to avoid
Figure 1. Study area in Lokern Natural Area, California, USA, showing
one of the dens used by each of the 11 individual female kit foxes and the
scat-collection transects we established in January 2008.
1458 The Journal of Wildlife Management N 74(7)
contamination from PCR products. We isolated each
sample L2 times and typed it L3 times to test for errors
and ambiguities in sex identification. Negative controls (no
scat material added to the extraction), used to check for
contamination, accompanied each set of extractions. We
also included positive controls from tissue samples of kit
foxes of known sexes in each set of PCR amplifications.
We determined the sex of the animal that deposited each
scat using a modification to an earlier protocol developed in
our laboratory by Ortega et al. (2004). Both methods use
primers that amplify a short (195 base pair [bp]) fragment of
the zinc finger protein genes (Zfx and Zfy). In kit foxes, this
fragment contains a TaqaI digestion site unique to the Zfy
gene. In an agarose gel, successful PCR products show a
double band for males and a single band for females (Ortega
et al. 2004). However, degraded samples with low quantities
of DNA produced PCR products that were difficult to
detect in agarose gels. To increase efficiency of screening
many fecal samples and to improve our ability to detect
fragments, we modified the original protocol by adding a
carboxyfluorescein label to the forward primer (ZFKF
203L) designed by Ortega et al. (2004) and by running
the digested PCR fragments directly onto an ABI PRISM*
3100 Genetic Analyzer (Applied Biosystems Inc., Foster
City, CA).
In our modified protocol, we performed PCR amplifica-
tions in an MJ Research PTC-100 thermocycler (MJ
Research, Waltham, MA) in 10-mL reaction volumes and
fluorescently labeled the forward primer (ZFKF 203L) with
6-FAM (Operon Technologies Inc., Alameda, CA). The
final reaction conditions were as follows: 0.5 U Ampli Taq
Gold DNA Polymerase (Applied Biosystems, Inc.), 13
AmpliTaq Buffer II, 0.4 mM fluorescently labeled forward
primer, 0.4 mM unlabeled reverse primer, 2 mM MgCl2,
0.2 mM each deoxyribonucleotide triphosphate, 103 bovine
serum albumin (New England Biolabs, Ipswich, MA), and 2?
3 mL of the DNA extract. Polymerase chain reaction
conditions and protocols for restriction enzyme digestion of
PCR products were the same as described in Ortega et al.
(2004); however, in our study, we added 1 mL of the digested
PCR product to 9 mL of formamide/ROX solution (Applied
Biosystems), electrophoresed and detected on an ABI
PRISM 3100 Genetic Analyser (Applied Biosystems). We
performed fragment size analysis using the GenotyperH 2.5 or
GeneMapperH software (Applied Biosystems). We deter-
mined samples to be males when L1 of 3 PCR amplifications
yielded 2 fragments (representing the 2 genes: the 154-bp
fragment [Zfx] and the 195-bp fragment [Zfy]) and females
when we consistently detected one fragment (representing
the Zfx gene) in L3 independent amplifications.
Our modified protocol was an effective way of processing
and detecting PCR products of Zfy and Zfx. With this
protocol, we loaded samples onto a 96-well plate and ran
them directly on an ABI PRISM 3100 Genetic Analyser for
2.5 hours. Although fluorescently labeled primers are more
expensive than unlabeled primers, peak detection of PCR
products with fluorescently labeled primers was more
sensitive and accurate than detection of bands and
determination of fragment size in an agarose gel using
ethidium bromide and ultraviolet fluorescence to visualize
the fragments.
RESULTS
We collected 547 fresh scats and successfully amplified DNA
from 432 of them (Table 1). Because we amplified DNA
samples L3 for each scat, we could estimate amplification
success and rates of allelic dropout when one of the 2
fragments failed to amplify in a particular reaction. Average
amplification success was 75.3% (range 73.3?77.3%) and we
found low rates of allelic dropout in January and February
(Table 1). We detected an increase in rates of allelic dropout
in the March samples, when 57 out of the 394 successful
PCR amplifications failed to amplify one of the 2 fragments.
Only 19 of the 57 reactions showed dropout for the 154-bp
fragment (Zfy) so most of the genotyping error (38/57 cases)
was due to dropout of the 195-bp fragment (Zfx). However,
if allelic dropout had introduced a bias against females in our
study, we should have observed a lower amplification success
in the month that had the most female scats (Jan) but this
was not the case.
We found similar numbers of scats each month but the sex
ratio varied across months (Table 1). In January, we found
58 male and 72 female scats, which was not different from
the expected 50:50 ratio (x2 5 1.66, P 5 0.280). In
February, we found almost 2 male scats for every female scat,
which was different than expected (x2 5 8.88, P 5 0.003),
and in March we found .8 male scats for every female scat,
which again was different than expected (x2 5 62.7, P 5 0).
Tabulating the number of male and female scats found on
each transect per month showed a high degree of
consistency in the trends over time across the 11 transects
(see Table S2, available at ,http://dx.doi.org/10.2193/
2009-401.s1.). We found more male scats on all 11
transects in March than in January (n 5 11, P , 0.001, sign
test) and we found fewer female scats on 10 of the 11
transects (n 5 10, P , 0.001, sign test).
DISCUSSION
We found and sexed approximately the same number of
scats each month, but the sex ratio changed markedly from
Table 1. Number of fresh kit fox scats we found and sexed in the Lokern Natural Area of California, USA, in 2008, number of male scats, number of female
scats, sex ratio, polymerase chain reaction amplification success, and allelic dropout rate each month.
Month No. found No. sexed M F Sex ratio % amplified Dropout
Jan 171 130 58 72 0.8:1 77.3 4.7
Feb 202 148 96 52 1.8:1 73.3 3.1
Mar 174 154 138 16 8.6:1 75.4 14.5
Ralls et al. N Changes in Sex Ratio of Fox Scats 1459
month to month, reflecting the expected equal sex ratio in
January but becoming increasingly male-biased in February
and March. As expected, the number of female scats we
found decreased each month, from 72 in January to 16 in
March. Unexpectedly, however, the number of male scats we
found increased each month, from 58 in January to 138 in
March. Because we collected only scats deposited by adults,
these results suggest that adults of both sexes showed
changes in fecal deposition patterns associated with the birth
of pups in late February or early March.
Male kit foxes bring food to females with young pups
(Moehrenschlager et al. 2004), and males likely spend more
time hunting when feeding their mates as well as
themselves. Males may deposit fewer scats near their den
and more scats in other areas of their home range, making
male scats more evenly dispersed and easier to find. In
contrast, females with young pups must change their
defecation behavior so that their scats are harder to find.
However, our suspicion that females might defecate near the
den during this period was incorrect. We continued to
monitor dens of the radiocollared females during the 2009
pupping season and found that there were no scats present at
dens when pups were still below ground. However, once
pups began to emerge aboveground at about 1 month of age
(as documented by direct observations or motion-triggered
cameras near dens), we found both pup and adult scats near
the den. Females with young pups may defecate in a latrine
chamber underground or in an aboveground latrine away
from the immediate vicinity of the den (Ralls and Smith
2004).
It is unlikely that our results can be explained by female
foxes depositing fewer scats during early lactation because of
fasting at this time. The use of maternal reserves as a
lactation strategy is only feasible in large mammals such as
bears, seals, and whales (Oftedal 2000). Small mammals
such as foxes expend energy at a much higher rate relative to
body mass than do large mammals; thus small mammals are
physically unable to store sufficient energy to cover the
energy expenditures associated with lactation for any length
of time (Oftedal 2000). In carnivores with litters, such as
foxes, lactation poses a large nutrient demand on mothers
and thus food intake increases with the onset of lactation
(Oftedal and Gittleman 1989); thus, one might expect that
more rather than fewer feces would be produced by lactating
females.
The effect of changes in fecal deposition patterns that we
observed on the results of surveys using fecal genotyping
would depend on the purpose of the survey. Contrary to our
initial hypothesis, surveys to determine distribution and
relative abundance of kit foxes, such as those by Smith et al.
(2006a) would not be affected, because the number of fresh
scats found per kilometer surveyed was similar across
months, ranging from 5.9 (130 scats/22 km) in January to
7 (154 scats/22 km) in March. However, detectability of
female scats in March was extremely low. Even though we
searched in areas known to be used by individual female
foxes, we found no scats in the home range of 3 of the 11
females and only one scat in the range of 4 others (see Table
S2, available at ,http://dx.doi.org/10.2193/2009-401.s1.).
Furthermore, the Lokern area has a high density of kit
foxes; Smith et al. (2006a) found about 25 scats/km
(counting both old and fresh scats) there during previous
surveys. We suspect that if we had conducted surveys in
March in an area with a low density of kit foxes, such as the
Ciervo-Panoche area where Smith et al. (2006a) found ,2
kit fox scats per kilometer in previous surveys, without
knowledge of the general areas used by individual females,
we would have failed to detect many females.
Although no noninvasive mark?recapture surveys for kit
foxes based on scats have been undertaken to date, such
surveys would be possible because kit fox scats can be
identified to the individual level based on microsatellite and
sex genotype (Smith et al. 2006b). Capture heterogeneity,
that is, differences in probability of finding scats of different
individuals, is an important consideration in mark?recapture
studies because it can lead to an underestimate of population
size (Otis et al. 1978). Substantial individual heterogeneity
in scat detection probability has been documented in bobcats
(Lynx rufus; Ruell et al. 2009) and wolves (Canis lupus;
Cubaynes et al. 2010). Capture heterogeneity can result
from individual differences in defecation rates, road use, or
territory marking, or variation in the quantity of DNA
found in scats of different individuals (Bellemain et al. 2005,
Eggert et al. 2005, Lukacs and Burnham 2005, Cubaynes et
al. 2010). Our results indicate that changes in individual
fecal deposition patterns associated with reproduction can be
an additional source of capture heterogeneity that should be
considered in the design of noninvasive surveys based on
scats. Even though detection heterogeneity can be modeled
if the survey design includes .2 sampling events, it is always
advisable to minimize it (Long and Zielinski 2008).
Detection heterogeneity associated with kit fox reproduction
could be avoided by scheduling sampling events for mark?
recapture surveys outside of the reproductive season. If
surveys are conducted during the reproductive season, mark?
recapture models that explicitly account for individual
detection heterogeneity, such as those developed by
Cubaynes et al. (2010), should be used to avoid underes-
timating population size. In noninvasive surveys for wolves,
models that ignored individual detection heterogeneity
underestimated population size by an average of 27%
(Cubaynes et al. 2010).
Changes in male and female defecation patterns during
the reproductive season may occur in other small canids,
such as swift foxes (Vulpes velox), in which males help care
for pups (Allardyce and Sovada 2003). Researchers collect-
ing scats of island foxes (Urocyon littoralis) on San Nicolas
Island, California, for diet studies found that scats were
much harder to find during the reproductive season, with
many fewer scats along roads than at other times of year,
which suggests that scats of male as well as female island
foxes are more difficult to find during the reproductive
season (C. Cory, The Nature Conservancy, personal
communication; F. Ferrara, Institute for Wildlife Studies,
personal communication). Changes may also occur in canid
species that live in larger social groups, because detection
1460 The Journal of Wildlife Management N 74(7)
probability of wolf scats was higher before than after the
breeding period (Cubaynes et al. 2010) and in females of
carnivore species that rear their young without male help.
For example, female mountain lions (Felis concolor) bury
their feces when they have young kittens (Seidensticker et al.
1973). More detailed studies of variation in defecation
patterns of other carnivore species during the reproductive
season may help improve accuracy of noninvasive surveys
based on feces.
MANAGEMENT IMPLICATIONS
Noninvasive survey methods are increasingly used to
determine animal presence and assess abundance. For
methods involving scats, heterogeneity in scat detection
rates among sex, age, or social classes could adversely affect
survey results. Around the time kit fox pups are born, both
parents appear to show changes in fecal deposition patterns
that make it easier to find male scats and harder to find
female scats. Effects of these changes on survey results will
vary depending on the purpose and design of the survey.
Surveys to determine distribution and relative abundance
would not be affected. However, if surveys to estimate
abundance are conducted during the reproductive season,
they could result in an underestimate of population size
unless the increased heterogeneity in scat detectability is
taken into account.
ACKNOWLEDGMENTS
We thank S. Phillips for preparing the figure, C. Asa, O.
Oftedal, and J. Seidensticker for helpful advice and
references, Rio for locating scats, and the Smithsonian
Institution?s Walcott Fund for financial support.
LITERATURE CITED
Allardyce, D., and M. A. Sovada. 2003. A review of the ecology,
distribution, and status of swift foxes in the United States. Pages 3?18 in
M. A. Sovada and L. Carbyn, editors. The swift fox: ecology and
conservation of swift foxes in a changing world. Canadian Plains
Research Center, Regina, Canada.
Bellemain, E., J. E. Swenson, D. Tallmon, S. Brunberg, and P. Taberlet.
2005. Estimating population size of elusive animals with DNA from
hunter-collected feces: four methods for brown bears. Conservation
Biology 19:150?161.
Cubaynes, S., R. Pradel, R. Choquet, C. Duchamp, J. Gaillard, J. Lebreton,
E. Marboutin, C. Miquel, A. Reboulet, C. Poillot, P. Taberlet, and O.
Gomenez. 2010. Importance of accounting for detection heterogeneity
when estimating abundance: the case of French wolves. Conservation
Biology 24:621?626.
Cypher, B. L., G. D. Warrick, M. R. M. Otten, T. P. O?Farrell, W. H.
Berry, C. E. Harris, T. T. Kato, P. M. McCue, J. H. Scrivner, and B. W
Zoellick. 2000. Population dynamics of San Joaquin kit foxes at the Naval
Petroleum Reserves in California. Wildlife Monographs 145.
Eggert, L. S., J. E. Maldonado, and R. C. Fleischer. 2005. Nucleic acid
isolation from ecological samples: animal scat and other associated
materials. Methods in Enzymology 395:73?87.
Egoscue, H. J. 1956. Preliminary studies of the kit fox in Utah. Journal of
Mammalogy 37:351?357.
Frantz, A. C., L. C. Pope, P. J. Carpenter, T. J. Roper, G. J. Wilson, and R.
J. Delahay. 2003. Reliable microsatellite genotyping of the Eurasian
badger (Meles meles) using faecal DNA. Molecular Ecology 12:1649?
1661.
Kohn, M. H., E. C. York, D. A. Kamradt, G. Haught, R. M. Sauvajot, and
R. K. Wayne. 1999. Estimating population size by genotyping faeces.
Proceedings of the Royal Society of London, Series B, Biological Sciences
266:657?663.
Long, R. A., P. MacKay, W. J. Zielinski, and J. C. Ray, editors. 2008.
Noninvasive survey methods for carnivores. Island Press, Washington,
D.C., USA.
Long, R. A., and W. J. Zielinski. 2008. Designing effective noninvasive
carnivore surveys. Pages 8?44 in R. A. Long, P. MacKay, W. J. Zielinski,
and J. C. Ray, editors. Noninvasive survey methods for carnivores. Island
Press, Washington, D.C., USA.
Lukacs, P. M., and K. P. Burnham. 2005. Review of capture-recapture
methods applicable to noninvasive genetic sampling. Molecular Ecology
14:3909?3919.
McKelvey, K. S., and M. K. Schwartz. 2004. Genetic errors associated with
population estimation using non-invasive molecular tagging: problems
and new solutions. Journal of Wildlife Management 68:439?448.
Miller, C. R., P. Joyce, and L. P. Waits. 2002. Assessing allelic dropout and
genotype reliability using maximum likelihood. Genetics 160:357?366.
Mills, L. S., J. J. Citta, K. P. Lair, M. K. Schwartz, and D. A. Tallmon.
2000. Estimating animal abundance using noninvasive DNA sampling:
promise and pitfalls. Ecological Applications 10:283?294.
Moehrenschlager, A., B. L. Cypher, K. Ralls, R. List, and M. A. Sovada.
2004. Comparative ecology and conservation priorities of swift and kit
foxes. Pages 185?198 in D. W. Macdonald and C. Sillero-Zubiri, editors.
Biology and conservation of wild canids. Oxford University Press,
Oxford, United Kingdom.
National Oceanic and Atmospheric Administration. 2009. National
Weather Service internet services team. Monthly precipitation for
Bakersfield, California. ,http://www.wrh.noaa.gov/hnx/bfl/normals/
bflrnyr.htm.. Accessed 7 Mar 2009.
Nelson, J. L., B. L. Cypher, C. D. Bjurlin, and S. Creel. 2007. Effects of
habitat on competition between kit foxes and coyotes. Journal of Wildlife
Management 71:1467?1475.
Oftedal, O. T. 2000. Use of maternal reserves as a lactation strategy in large
mammals. Proceedings of the Nutrition Society 59:99?106.
Oftedal, O. T. and J. L. Gittleman. 1989. Patterns of energy output during
reproduction in carnivores. Pages 355?378 in J. L. Gittleman, editor.
Carnivore behavior, ecology, and evolution. Cornell University Press,
Ithaca, New York, USA.
Ortega, J., M. R. Franco, B. A. Adams, K. Ralls, and J. E. Maldonado.
2004. A reliable, noninvasive method for sex determination in the
endangered San Joaquin kit fox (Vulpes macrotis mutica) and other canids.
Conservation Genetics 5:715?718.
Otis, D. L., K. P. Burnham, G. C. White, and D. R. Anderson. 1978.
Statistical inference from capture data on closed animal populations.
Wildlife Monographs 62.
Prugh, L. R., C. E. Ritland, S. M. Arthur, and C. J. Krebs. 2005.
Monitoring coyote population dynamics by genotyping faeces. Molecular
Ecology 14:1585?1596.
Ralls, K., B. Cypher, and L. K. Spiegel. 2007. Social monogamy in kit
foxes: formation, association, duration, and dissolution of mated pairs.
Journal of Mammalogy 88:1439?1446.
Ralls, K., and D. A. Smith. 2004. Latrine use by San Joaquin kit foxes
(Vulpes macrotis mutica) and coyotes (Canis latrans). Western North
American Naturalist 64:544?547.
Ruell, E. W., S. P. D. Riley, M. R. Douglas, J. P. Pollinger, and K. R.
Crooks. 2009. Estimating bobcat population sizes and densities in a
fragmented urban landscape using noninvasive capture-recapture sam-
pling. Journal of Mammalogy 90:129?135.
Schwartz, M. K., and S. L. Monfort. 2008. Genetic and endocrine tools for
carnivore surveys. Pages 238?262 in R. A. Long, P. MacKay, W. J.
Zielinski, and J. C. Ray, editors. Noninvasive survey methods for
carnivores. Island Press, Washington, D.C., USA.
Seidensticker, J. C. IV, M. G. Hornocker, W. V. Wiles, and J. P. Messick.
1973. Mountain lion social organization in the Idaho Primitive Area.
Wildlife Monographs 35.
Smith, D. A., K. Ralls, B. L. Cypher, H. O. Clark, Jr., P. A. Kelly, D. F.
Williams, and J. E. Maldonado. 2006a. Relative abundance of
endangered San Joaquin kit foxes (Vulpes macrotis mutica) based on
scat-detection dog surveys. Southwestern Naturalist 51:210?219.
Smith, D. A., K. Ralls, A. Hurt, B. Adams, M. Parker, B. Davenport, M.
C. Smith, and J. E. Maldonado. 2003. Detection and accuracy rates of
dogs trained to find scats of San Joaquin kit foxes. Animal Conservation
6:339?346.
Ralls et al. N Changes in Sex Ratio of Fox Scats 1461
Smith, D. A., K. Ralls, A. Hurt, B. Adams, M. Parker, and J. E.
Maldonado. 2006b. Assessing reliability of microsatellite genotypes from
kit fox faecal samples using genetic and GIS analyses. Molecular Ecology
15:387?406.
Spiegel, L. K. 1996. Studies of the San Joaquin kit foxes in undeveloped
and oil-developed areas. California Energy Commission, Sacramento,
USA.
Taberlet, P., S. Griffin, B. Goossens, S. Questiau, V. Manceau, N.
Escaravage, L. P. Waits, and J. Bouvet. 1996. Reliable genotyping of
samples with very low DNA quantities using PCR. Nucleic Acids
Research 24:3189?3194.
Zoellick, B. W., T. P. O?Farrell, P. M. McCue, C. E. Harris, and T. T.
Kato. 1987. Reproduction of the San Joaquin kit fox on Naval Petroleum
Reserve #1, Elk Hills, California, 1980?1985. U.S. Department of
Energy Topical Report No. EGG 102822144. EG&G Energy
Measurements, Goleta, CA.
Associate Editor: Latch.
1462 The Journal of Wildlife Management N 74(7)