Effects of Roads on Endangered San Joaquin Kit Foxes

ABSTRACT San Joaquin kit foxes (Vulpes macrotis mutica) occur in central California, USA, and are endangered due to habitat loss and degradation. As the human population of California grows, more roads are being constructed in remaining kit fox habitat. We examined effects of 2-lane roads on demographic and ecological patterns of kit foxes on the Lokern Natural Area (LNA) from August 2001 to June 2004. Of 60 radiocollared kit foxes, only one was struck by a vehicle. Foxes were assigned to 1 of 3 risk categories (high, medium, or low) based on proportion of time spent in road-effect zones, which were defined by the probability of a fox encountering a road during nocturnal movements. Fox survival probabilities, reproductive success, litter size, nocturnal movements, and den placement all were similar among risk categories. Nocturnal locations of foxes were closer to roads than were den locations, and den fidelity was lowest for medium-risk foxes and highest for low-risk foxes but intermediate for high-risk foxes. Food availability and use were not affected by proximity to roads. We were unable to detect any significant detrimental effects from 2-lane roads on kit fox demography and ecology. Our results suggest that standard mitigation strategies, such as crossing structures and exclusionary fencing, would not benefit kit foxes on the LNA.     

Lynx (Lynx lynx) killing red foxes (Vulpes vulpes) in boreal Sweden – frequency and population effects

We studied the frequency and pattern of lynx Lynx lynx predation on red foxes Vulpes vulpes in boreal Sweden by the radio tracking of foxes and the snow tracking of lynx. We also assessed the population trend of red foxes after the re-establishment of lynx in the region, based on various population indices. Fifty per cent of recorded fox mortalities in the radio-tracking study (four of eight) were lynx kills. Adult-sized foxes killed by lynx during radio tracking were in normal condition and of prime age, and were killed after the assumed annual population bottleneck. Albeit based on a small number of kills, this pattern may suggest that lynx predation, at least to some extent, is additive to other mortality in foxes. The annual lynx predation rate was 14% on radio-tracked foxes and 4% on snow-tracked foxes. The population indices of foxes in the main study area decreased by about 10% annually during the study period. The population decrease could potentially be explained by lynx predation alone, but we acknowledge some alternative explanations. Our results point out the possibility that red fox populations can be significantly limited by allowing lynx populations to recover.     

Ecological and biological factors involved in the transmission of Echinococcus multilocularis in the French Ardennes

In order to identify the respective importance of the ecological and biological factors involved in the transmission of Echinococcus multilocularis, we estimated grassland vole intermediate host (Microtus sp. and Arvicola terrestris) population densities, in relation to the diet of the definitive host (red fox, Vulpes vulpes) and with the prevalence of E. multilocularis in the fox population. The study was conducted in the Ardennes, north-eastern France, which is an area with a high incidence of alveolar echinococcosis. Surface index methods showed that Microtus was the most abundant intermediate host in the area. Furthermore, Microtus was present in one-third of the 144 faeces and 98 stomach content samples examined and represented more than two-thirds of the rodent occurrences. Red fox predation on Microtus was significantly correlated with Microtus relative abundance. In contrast, the relative abundance of A. terrestris was very low. This species, as well as Clethrionomys glareolus and Apodemus sp., was little consumed. E. multilocularis prevalence in foxes was determined from carcasses and reached 53% (95% confidence interval 45-61%). Intensity of infection varied from 2 to 73,380 worms per fox, with 72% of the sampled worm burden harboured by 8% of the sampled foxes. The selected explanatory variables (sex, year, age class, health and nutritional condition, and season) failed to predict prevalence rate and worm burden. The high prevalence rate in foxes indicates the possibility of intense E. multilocularis transmission, apart from periods, or in landscapes, favourable to large population outbreaks of grassland rodents.     

Distribution, habitat utilization and age structure of a suburban fox (Vulpes vulpes) population

The occurrence of wild foxes in suburbia is discussed. It is shown that in London breeding populations of foxes are found 5 km from the city centre, and in the last 3 years foxes have been recorded in the very centre of the city. The fox population in London is shown to be heavily dependent on residential habitats for both daytime harbourage and when selecting sites for natal earths. The fox population is unevenly distributed in London, with a marked clumping of the adult population during most of the year. The age structure of the population is presented, and these data are compared with data for other canid populations. Conclusions are drawn as to the effects of conventional control techniques on the age structure of a fox population.     

High genetic diversity and low population structure in red foxes (Vulpes vulpes) from Croatia

The red fox (Vulpes vulpes) is a highly adaptable omnivorous mammal distributed across all continents on the northern hemisphere. Although the red fox is present throughout Europe, where it plays an important ecological and socio-economic role not only as a game species but also as a rabies reservoir, few studies have examined its population-level mitochondrial DNA variability. In this study, 27 mitochondrial DNA control region haplotypes were identified in 229 red fox samples taken from four regions in Croatia. Haplotype diversity of Croatian red foxes (0.901) was found to be among the highest of all European red fox populations studied to date. Genetic differentiation among regions was quite low, and statistically significant estimates of differentiation were obtained only when comparing the population from the peninsular region of Istria with the three continental populations. It seems that landscape barriers like rivers and small mountains do not restrict gene flow among foxes in the continental part of Croatia, while the combination of a narrow land bridge and altitudes exceeding 1000 m limit fox migration between Istria and the rest of the continent. Better understanding of small-scale population structure will require analysis of highly variable nuclear markers like microsatellites.     

Biochemical and hematologic reference intervals for the endangered island fox (Urocyon littoralis)

Hematologic and serum biochemical data collected must be interpreted by comparison with normal reference intervals generated from healthy animals, within a similar population, because many blood parameters are influenced by diet, environment, and stress. Species-specific reference intervals for the endangered island fox (Urocyon littoralis) are not available. We reviewed hematology and serum biochemistry panels from 280 island foxes sampled from 1999-2008 and established normal reference intervals from clinically healthy foxes using a nonparametric approach. Blood parameters were analyzed for differences in age, sex, island of origin, and captivity status. Alkaline phosphatase, alanine aminotransferase, aspartate aminotransferase, and creatine kinase activities, as well as calcium and phosphorus concentrations, were significantly higher in juveniles than in adults, but total protein and globulin concentration was lower for juveniles than for adults. Lymphocyte and eosinophil counts, and blood urea nitrogen (BUN) concentration, in foxes from the northern Channel islands of California, USA (Santa Cruz, Santa Rosa, and San Miguel) were higher when compared with foxes from Santa Catalina Island to the south. Higher lymphocyte and eosinophil numbers in the northern island foxes may be associated with increased levels of parasitism on the northern islands. Differences in BUN concentration in both free-ranging and captive foxes may reflect dietary differences among islands. Although aggressive conservation programs have been enacted, island foxes are still susceptible to infectious and neoplastic diseases and, potentially, to toxins. Island fox species-specific reference intervals will enable managers and veterinarians to better care for sick and injured foxes and will contribute to future population health monitoring.     

Exclusion by interference competition? The relationship between red and arctic foxes

The distribution of many predators may be limited by interactions with larger predator species. The arctic fox in mainland Europe is endangered, while the red fox is increasing its range in the north. It has been suggested that the southern distribution limit of the arctic fox is determined by interspecific competition with the red fox. This has been criticised, on the basis that the species co-exist on a regional scale. However, if the larger red fox is superior and interspecific competition important, the arctic fox should avoid close contact, especially during the breeding season. Consequently, the distribution of breeding dens for the two species would be segregated on a much smaller spatial and temporal scale, in areas where they are sympatric. We tested this hypothesis by analysing den use of reproducing arctic and red foxes over 9 years in Sweden. High quality dens were inhabited by reproducing arctic foxes more often when no red foxes bred in the vicinity. Furthermore, in two out of three cases when arctic foxes did reproduce near red foxes, juveniles were killed by red foxes. We also found that breeding arctic foxes occupied dens at higher altitudes than red foxes did. In a large-scale field experiment, red foxes were removed, but the results were not conclusive. However, we conclude that on the scale of individual territories, arctic foxes avoid areas with red foxes. Through interspecific interference competition, the red fox might thus be excluding the arctic fox from breeding in low altitude habitat, which is most important in years when food abundance is limited and competition is most fierce. With high altitude refuges being less suitable, even small-scale behavioural effects could scale up to significant effects at the population level.     

On food preference in the Red fox

• 1 Foxes treat different prey species in a variety of ways, eating, burying, or discarding them on the basis of preference.
• 2 Because foxes often utilize cached food and because they can remember which prey species is in a given cache the preference effect can be longstanding.
• 3 Evidence from the literature suggests that comparable effects of preference for different species of small mammals affects the diet of wild foxes and their behaviour in the same way as demonstrated in these experiments.
• 4 Certain distastes appear common to all foxes and most carnivores, for instance, insectivore and carnivore meat, in particular that of their own species.
• 5 An incidence of active cannibalism by a fox is reported.
• 6 The effect of food preference is shown to change during the course of one individual's life perhaps as a consequence of such factors as rearing cubs and competition for food.
• 7 One effect of the behavioural consequences of food preference is to defer the decision of what to eat.
• 8 That the fox will kill animals that it does not eat means that populations of animals that are not strictly fox prey are still at risk from fox predatory activity.

     

Do Exotic Vertebrates Structure the Biota of Australia? An Experimental Test in New South Wales

From 1993 to 2001, we conducted a series of experiments in a mixed grassland–woodland system in central New South Wales (NSW) to quantify the interactions between red foxes and their prey and competitors. Foxes were removed from two areas around the perimeter of Lake Burrendong, and data were collected from these areas and a nearby untreated area before, during, and after the period of fox control. The arrival of rabbit hemorrhagic disease (RHD) in 1996 provided an opportunity to examine the interactive effects of controlling foxes and rabbits. In this landscape, typical of central NSW, (a) the fox population was not affected by a large reduction in the abundance of rabbits, or vice versa; (b) the cat population declined in areas where foxes were removed after the large RHD-induced reduction in rabbit numbers, but there was no consistent response to the removal of foxes; (c) the abundance of some macropod species increased in response only to the combined removal of rabbits and foxes; (d) there were no consistent changes in the abundances of bird species in response to the removal of either foxes or rabbits, but there were clear habitat differences in bird species richness; and (e) there was likely to be an increase in woody plant species after the large reduction in rabbit populations by RHD. We conclude that (a) long-term field experiments (more than 3 years) are required to quantify the indirect consequences of controlling foxes and rabbits, and (b) single manipulations, such as fox control or rabbit control, are not necessarily sufficient for the conservation of remnant woodland communities in southeastern Australia.     

Genetic diversity in a reintroduced swift fox population

Swift fox (Vulpes velox) were historically distributed in southwestern South Dakota including the region surrounding Badlands National Park (BNP). The species declined during the mid-1800s, largely due to habitat loss and poisoning targeted at wolves (Canis lupus) and coyotes (Canis latrans). Only a small population of swift foxes near Ardmore, which is located in Fall River County, South Dakota, persisted. In 2003, a reintroduction program was initiated at BNP with swift foxes translocated from Colorado and Wyoming. Foxes released in the years 2003, 2004 and 2005 were translocated from Colorado (BNP-Colorado) whereas in 2006, released foxes were translocated from Wyoming (BNP-Wyoming). Our objective was to evaluate genetic diversity and structure of the restored swift fox population in the area surrounding BNP compared to source fox populations in an area of Colorado and Wyoming, as well as the local swift fox population neighboring BNP near Ardmore in Fall River County, South Dakota. A total of 400 swift foxes (28 released in 2003, 28 released in 2004, 26 released in 2005, 26 released in 2006, 252 wild-born foxes, 40 individual foxes from the Ardmore area of South Dakota) was genotyped using twelve microsatellite loci. We report mean gene diversity values of 0.778 (SD = 0.156) for the BNP-Colorado population, 0.753 (SD = 0.165) for the BNP-Wyoming population, 0.751 (SD = 0.171) for the BNP population, and 0.730 (SD = 0.166) for the Fall River population. We also obtained F_st values ranging from 0.014 to 0.029 for pair-wise comparisons of fox populations (BNP, Fall River, BNP-Wyoming, BNP-Colorado). We conclude that the reintroduced fox population around BNP has high genetic diversity comparable to its source populations in Colorado and Wyoming. Although genetic diversity indicates that the reintroduction was successful, additional time is necessary to fully evaluate long-term genetic maintenance and interconnectivity among these populations.     

Survival and Cause-Specific Mortality of Corsac and Red Foxes in Mongolia

ABSTRACT The corsac fox (Vulpes corsac) and red fox (Vulpes vulpes) range widely across northern and central Asia and may be declining in many regions due to overhunting and other causes. However, details of the fundamental causes of survival and mortality of both species remain largely unquantified, but may be crucial for understanding interspecific relationships and developing effective conservation actions. We studied a radiomarked population of sympatric corsac and red foxes in central Mongolia to quantify survival and cause-specific mortality rates from April 2005 to April 2007. Survival probability was 0.34 for corsacs (n = 18) and 0.46 for red foxes (n = 17) and did not vary by year within or between each species. Among both foxes, mortality occurred mainly from hunting by humans, but also from predation by larger canids and unknown causes. Our results suggest that illegal human hunting represents the principal source of mortality for both species and that a recently initiated ranger patrol program in the study area did not affect fox survival. As such, more stringent protective measures will likely be necessary to halt declines of both foxes. Our results also suggest that interference competition occurs between species as red foxes killed but did not consume corsacs. Our results will be useful for developing science-based management strategies to protect foxes in Mongolia, and in understanding the competitive relationships between them.     

Effects of Coyote Population Reduction on Swift Fox Demographics in Southeastern Colorado

ABSTRACT The distribution and abundance of swift foxes (Vulpes velox) has declined from historic levels. Causes for the decline include habitat loss and fragmentation, incidental poisoning, changing land use practices, trapping, and predation by other carnivores. Coyotes (Canis latrans) overlap the geographical distribution of swift foxes, compete for similar resources, and are a significant source of mortality amongst many swift fox populations. Current swift fox conservation and management plans to bolster declining or recovering fox populations may include coyote population reduction to decrease predation. However, the role of coyote predation in swift fox population dynamics is not well-understood. To better understand the interactions of swift foxes and coyotes, we compared swift fox population demographics (survival rates, dispersal rates, reproduction, density) between areas with and without coyote population reduction. On the Piñon Canyon Maneuver Site, Colorado, USA, we monitored 141 swift foxes for 65,226 radio-days from 15 December 1998 to 14 December 2000 with 18,035 total telemetry locations collected. Juvenile swift fox survival rate was increased and survival was temporarily prolonged in the coyote removal area. Adult fox survival patterns were also altered by coyote removal, but only following late-summer coyote removals and, again, only temporarily. Coyote predation remained the main cause of juvenile and adult fox mortality in both areas. The increase in juvenile fox survival in the coyote removal area resulted in a compensatory increase in the juvenile dispersal rate and an earlier pulse in dispersal movements. Adult fox dispersal rate was more consistent throughout the year in the coyote removal area. Coyote removal did not influence the reproductive parameters of the swift foxes. Even though juvenile survival increased, swift fox density remained similar between the areas due to the compensatory dispersal rate among juvenile foxes. We concluded that the swift fox population in the area was saturated. Although coyote predation appeared additive in the juvenile cohort, it was compensatory with dispersal.     

Evolutionary and climatic factors affecting tooth size in the red foxVulpes vulpes in the Holarctic

Research into the geographical pattern of tooth size in the red fox,Vulpes vulpes (Linnaeus, 1758) in the Holarctic was conducted on a sample of 3806 skulls belonging to 41 fox populations. The Nearctic was represented by 948 specimens (249 females, 359 males, 340 specimens of unknown sex) belonging to 13 populations, whereas the Palearctic was represented by 2858 red foxes (1034 females, 1256 males, 568 specimens of unknown sex) from 32 populations. In the Nearctic, the largest foxes live on Kodiak Island (V. v. harrimani) and the Kenai Peninsula (V. v. kenaiensis), while the smallest ones live in California (V. v. necator) and Georgia (V. v. fulvus). In the Palearctic, the largest foxes come from the Far East (V. v. jakutensis, V. v. beringiana, V. v. tobolica), while the smallest are from the southern borders of the Eurasian range (V. v. pusilla, V. v. barbara, V. v. arabica). In both the Palearctic and Nearctic, tooth size in the fox varies depending on the geo-climatic factors. The fox’s tooth size confirms the general basis of Bergmann’s rule. In the Palearctic, specimens with larger teeth occur in cooler habitats with greater seasonality. These are first and foremost Northern and Far Eastern populations. In the Nearctic, tooth size in red foxes depends on the temperature and humidity of their habitat. Competition within the species and between species has important impact on the variation and dimorphism of tooth size in the red fox. Both in the Nearctic and Palearctic, red foxes from regions of sympatric co-occurrence with other closely relatedVulpes species, are more sexually dimorphic in terms of tooth size than red foxes from allopatric regions. Analysis of morphological distance on the basis of the size of dental characteristics shows, that in the Palearctic, the foxes from India (V. v. pusilla), while in the Nearctic, the population from Kodiak Island (V. v. harrimani) are most distant from the remaining populations. Geographic barriers such as the Bering Strait, Parry Channel, Mackenzie River, Kolyma and Omolon River systems have had a critical impact on red fox evolution. The most likely place for the evolution and diversification of the phyletic lineVulpes vulpes seems to be the Middle East region.     

Genetic tagging reveals a significant impact of poison baiting on an invasive species

Globally, invasive predators are major pests of agriculture and biodiversity and are the focus of comprehensive control programs. Because these species are typically elusive, wary of traps, and occur at low densities, their fundamental population dynamics are difficult to determine and quantitative evaluations of control programs are rarely conducted. Noninvasive DNA analysis has the potential to resolve this long-standing limitation to pest management. We carried out a landscape-scale experiment to quantify reduction in the abundance of a red fox (Vulpes vulpes) population when baited with sodium fluoroacetate (1080) poison (the most widely used method of fox control in Australia). We collected fox hairs with hair snares during 4 4-day sessions over the course of 6 months at a site in semi-arid Western Australia. The first session took place in late summer just prior to when juvenile foxes typically disperse, and the final session followed aerial baiting with 1080 poison. We obtained consensus microsatellite genotypes from 196 samples, and used them to conduct both spatially explicit and open model capture–recapture analysis. Twenty-eight percent of trap nights yielded hair samples suitable for identification of individual foxes, which is more than an order of magnitude greater than trapping rates reported with conventional techniques. Fox density changed little during 3 pre-baiting sessions and averaged 0.73 foxes/km² (±0.33 SE), which is less than most previous trap-based estimates for Australian foxes. Density dropped significantly in response to baiting to 0.004 foxes/km². Prior to baiting, the apparent survival of foxes remained static (0.72 ± 0.14 SE), but in response to baiting it dropped precipitously and was effectively zero. This experiment provides the first quantitative assessment of the effectiveness of 1080 poison baiting for reducing fox density, and in this case demonstrates it to be a highly effective method for culling foxes from a region. Further, it demonstrates that noninvasive DNA analysis will provide significantly more data than conventional trapping methods. This method is likely to provide greater precision and accuracy than conventional methods and therefore result in more robust evaluations of management strategies for the fox in Australia, and for cryptic species elsewhere. © 2011 The Wildlife Society.     

Genetic footprints reveal geographic patterns of expansion in Fennoscandian red foxes

Population expansions of boreal species are among the most substantial ecological consequences of climate change, potentially transforming both structure and processes of northern ecosystems. Despite their importance, little is known about expansion dynamics of boreal species. Red foxes (Vulpes vulpes) are forecasted to become a keystone species in northern Europe, a process stemming from population expansions that began in the 19th century. To identify the relative roles of geographic and demographic factors and the sources of northern European red fox population expansion, we genotyped 21 microsatellite loci in modern and historical (1835–1941) Fennoscandian red foxes. Using Bayesian clustering and Bayesian inference of migration rates, we identified high connectivity and asymmetric migration rates across the region, consistent with source‐sink dynamics, whereby more recently colonized sampling regions received immigrants from multiple sources. There were no clear clines in allele frequency or genetic diversity as would be expected from a unidirectional range expansion from south to north. Instead, migration inferences, demographic models and comparison to historical red fox genotypes suggested that the population expansion of the red fox is a consequence of dispersal from multiple sources, as well as in situ demographic growth. Together, these findings provide a rare glimpse into the anatomy of a boreal range expansion and enable informed predictions about future changes in boreal communities.     

Assessment of rabbit hemorrhagic disease in controlling the population of red fox: A measure to preserve endangered species in Australia

Predator's management requires a detailed understanding of the ecological circumstances associated with predation. Predation by foxes has been a significant contributor to the Australian native animal reduction. This paper mainly focuses on the dissemination of rabbit hemorrhagic disease in the rabbit population and its subsequences on red fox (Vulpes vulpes) population, by qualitative and quantitative analyses of a designed eco-epidemiological model with simple law of mass action and sigmoid functional response.Existence of solution has been analyzed and shown to be uniformly bounded. The basic reproduction number (R₀) is obtained and the occurrence of a backward bifurcation at R₀ = 1 is shown to be possible using central manifold theory. Global stability of endemic equilibrium is established by geometric approach. Criteria for diffusion-driven ecological instability caused by local random movements of European rabbits and red fox are obtained. Detailed analyses of Turing patterns formation selected by reaction-diffusion system under zero flux boundary conditions are presented. We found that transmission rate, self and cross-diffusion coefficients have appreciable influence on spatial spread of epidemics. Numerical simulation results confirm the analytical finding and generate patterns which indicate that population of red foxes might be controlled if rabbit hemorrhagic disease (RHD) is introduced into the rabbit population and thus ecological balance can be maintained.     

When the Ghost of Predation has Passed: Do Rodents from Islands with and without Fox Predators Exhibit Aversion to Fox Cues?

Anti‐predator behavior can alter the dynamics of prey populations, but little is known about the rate at which anti‐predator behavior is lost from prey populations following predator removal. The Channel Islands differ in whether they have historically contained a top predator, the Island Fox (Urocyon littoralis), in evolutionary time (approximately 6200–10 000 yr). On a historically fox‐containing island and two historically fox‐free islands in 2007, I deployed live traps that contained olfactory cues of fox predators (fox feces), olfactory cues of an herbivore (horse feces) or a no‐feces control. Due to a captive breeding program, foxes on the historically fox‐containing island were effectively removed from 1998 to 2004. Rodents from one of the historically fox‐free islands did not respond to fox cues, whereas rodents on the historically fox‐containing island were more likely to be captured in a control trap and less likely to be captured in a fox‐cue trap. Results from the other historically fox‐free island that experienced a recent population bottleneck and period of captive rearing exhibited a preference for horse‐scented traps. These results suggest that, on islands where foxes are the primary predators, anti‐predator behavior in response to olfactory cues is not likely to be rapidly lost by short‐term removals of foxes, although the nature of anti‐predator behavior may depend upon founder events and recent population dynamics (e.g. population bottlenecks or several generations in captivity).     

Spatial and temporal variation in the seroprevalence of canine heartworm antigen in the island fox

Island foxes (Urocyon littoralis) are endemic to six of the eight California Channel Islands (USA). The island fox is classified as a threatened species by the State of California, and recently three of the six subspecies have experienced abrupt population declines. As part of a continuing effort to determine the cause of the declines, we tested island fox serum samples collected in 1988 (n = 176) and 1997-98 (n = 156) over the entire geographic range of the species for seroprevalence of canine heartworm (Dirofilaria immitis) antigen. Using a commercially available enzyme-linked immunosorbent assay (PetChek, Idexx Laboratories, Westbrook, Maine, USA) we detected heartworm antigen in four of the six populations of island foxes. On San Miguel and Santa Rosa Islands, seroprevalence in adult foxes was >85% (n = 62) in 1988 and increased to 100% (n = 24) in 1997-98. On Santa Cruz Island, seroprevalence in adult foxes decreased from 83% (n = 30) to 58% (n = 26), whereas on San Nicolas Island, seroprevalence increased from 25% (n = 32) to 77% (n = 30) during the same period. All of the pups assayed (n = 33) were seronegative. The seroprevalences of heartworm reported herein for the four populations of island foxes are the highest yet reported for a fox species. However, additional demographic data reported elsewhere suggests that heartworm has not been a major factor in the recent declines of island fox populations.     

The city-fox phenomenon: genetic consequences of a recent colonization of urban habitat

The red fox (Vulpes vulpes) is one of the best-documented examples of a species that has successfully occupied cities and their suburbs during the last century. The city of Zurich (Switzerland) was colonized by red foxes 15 years ago and the number of recorded individuals has increased steadily since then. Here, we assessed the hypothesis that the fox population within the city of Zurich is isolated from adjacent rural fox populations against the alternative hypothesis that urban habitat acts as a constant sink for rural dispersers. We examined 11 microsatellite loci in 128 foxes from two urban areas, separated by the main river crossing the city, and three adjacent rural areas from the region of Zurich. Mean observed heterozygosity across individuals and the number of detected alleles were lower for foxes collected within the city as compared with their rural conspecifics. Genetic differentiation was significantly lower between rural than between rural and urban populations, and highest value of pairwise FST was recorded between the two urban areas. Our results indicate that the two urban areas were independently founded by a small number of individuals from adjacent rural areas resulting in genetic drift and genetic differentiation between rural and urban fox populations. Population admixture and immigration analysis revealed that urban-rural gene flow was higher than expected from FST statistics. In the five to seven generations since colonization, fox density has dramatically increased. Currently observed levels of migration between urban and rural populations will probably erode genetic differentiation over time.