Urocyon Littoralis Research Articles

A landscape-based approach for delineating hotspots of wildlife-vehicle collisions

Imposing human perceptions about the scales of ecological processes can produce unreliable scientific inferences in wildlife research and possibly misinform mitigation strategies. An example of this disconnect occurs in studies of wildlife-vehicle collisions (WVCs). Subjective procedures are often used to delineate hotspots of WVCs, resulting in hotspots that are not spatially independent. We developed a new approach that identifies independent hotspots using attributes of the landscape to inform delineations instead of subjective measures. First, we generated a candidate set of grouping scenarios using unique combinations of kernel-density estimation parameterization (i.e., bandwidth and isopleth values). Next, we associated the groups of WVCs with attributes of the surrounding landscape. Finally, we identified the grouping scenario with the highest amount of variation in the landscape among the groups. The highest variation corresponded to hotspots that were most distinguishable from each other (i.e., most independent) based on the surrounding landscape. We tested our approach on 3 species of wildlife [island foxes (Urocyon littoralis) on San Clemente Island, CA; white-tailed deer (Odocoileus virginianus) in Onondaga County, NY; and moose (Alces alces) in western Maine] that exemplified varying degrees of space-use in different landscapes. We found that the landscape-based approach was able to effectively delineate independent hotspots for each species without using subjective measures. The landscape-based approach delineated fewer or larger hotspots than currently used methods, suggesting a reduction in spatial dependency among hotspots. Variation in the landscape indicated that hotspots may be larger than previously identified; therefore current mitigation strategies should be adjusted to include larger areas of high risk.

On the Fast Track to Recovery: Island Foxes on the Northern Channel Islands

The island fox (Urocyon littoralis) represents an unusual case of a species that achieved virtual recovery a mere 15 years after population declines were first discovered. Island fox subspecies on San Miguel, Santa Rosa, and Santa Cruz islands declined precipitously in the mid-1990s due to predation by Golden Eagles (Aquila chrysaetos), which had not historically bred on the islands. In 2008, a 10-year period of recovery action implementation ended. The recovery program had included captive breeding and reintroduction of island foxes and capture and relocation of Golden Eagles. Free-ranging fox populations have been monitored to assess recovery of each subspecies and to detect potential threats of disease and predation. Monitoring included (1) annual grid trapping to allow estimation of annual population size via capture-mark-recapture methods and (2) systematic surveillance of radio-collared foxes to allow estimation of mortality rates and causes. A comprehensive demographic modeling effort produced a population recovery tool that uses adult mortality and population size estimates from the monitoring programs to estimate extinction risks for each fox population. The tool allows managers to assess when threats are sufficiently mitigated to consider populations acceptably safe from extinction. Population monitoring indicates that island foxes on the northern Channel Islands have increased up to 30-fold from population lows and that annual survival has been 90% or better in most years. The San Miguel and Santa Cruz subspecies have approached or reached predecline population levels, and application of the recovery tool indicates they will be biologically recovered by 2013. Biological recovery of the Santa Rosa subspecies, hindered by predation which caused lower survival in 2010, will occur by 2017.

Evaluation of New Telemetry Technologies for Research on Island Foxes

Abstract. New telemetry technologies have recently become available for research on island foxes (Urocyon littoralis). These include GPS units, which collect location data, and proximity logger units, which record contacts between individuals. We evaluated these technologies on island foxes through 4 field studies. GPS collars were deployed on foxes on Santa Catalina during 2007–2008 (n = 20) and 2010–2011 (n = 5) and on Santa Rosa during 2009–2010 (n = 14). The GPS units had multiple issues including malfunctioning drop-off mechanisms, failure of some units to yield data, low location acquisition rates, improper factory programming, high rates of premature failure of VHF transmitters and GPS units, poor VHF signal strength, faulty mortality sensors, and breakage of the unit housing or antenna. Proximity loggers were deployed on foxes on San Miguel during 2009–2010 (n = 17). Performance was satisfactory and consistent with expectations. Both the GPS and proximity logger units yielded high-quality data whe...

Status of the Santa Catalina Island Fox Thirteen Years after Its Decline

Santa Catalina Island was home to an estimated 1342 adult island foxes (Urocyon littoralis catalinae) in 1990. Nine years later, fox sightings declined and reports of dead or dying foxes increased. An island-wide trapping effort was initiated after a fox carcass tested positive for Canine distemper virus (CDV). In 1999, only 10 foxes were captured east of the Two Harbors isthmus during 1046 trap-nights. A multifaceted conservation plan was implemented in 2000 to conserve the Santa Catalina population of island fox. Initial recovery actions took place from 2000 to 2005 and resulted in the translocation of 22 juvenile foxes from the unaffected West End of the island to the depopulated eastern portion, the production and release of 37 pups from the captive breeding facility, and the vaccination of >80% of the wild fox population against CDV. Since 2006, fox recovery activities have included an annual island-wide population survey, vaccination of 300 foxes per year, weekly mortality monitoring of 50 radio-collared individuals, blood sampling to monitor the prevalence of CDV, veterinary treatment of injured foxes, and public outreach. Low mortality rates, successful breeding in the wild, and mitigation of the original cause of decline allowed for Catalina's fox population to grow to an estimated 1115 adults by 2012 and to be considered biologically recovered. The outbreak of another virulent canine disease on Santa Catalina Island, such as CDV or rabies, continues to be the greatest threat to the long-term survival of U. l. catalinae due to the species' restricted distribution and small population size, as well as the continued presence of domestic dogs on the island.

Status, Distribution, and Conservation of Scripps's Murrelet at Santa Catalina Island, California

The small population of Scripps's Murrelets (Synthliboramphus scrippsi) at Santa Catalina Island, California, has been restricted for at least several millennia to isolated pairs nesting in cliff and shoreline habitats that are mostly inaccessible to island fox (Urocyon littoralis catalinae). Prior to 1994, the only evidence of murrelets breeding at Catalina was a single nest reportedly found on Bird Rock in 1967. In 1994–1995, a larger and more widespread population estimated at 25–75 pairs was indicated through vocal detection surveys of murrelets attending nocturnal at-sea congregations in nearshore waters near breeding areas. Murrelets were heard at 11 of 25 survey stations, with highest vocal activity between Land's End and Ribbon Rock (6–62 detections per survey). In 2004 and 2012, round-island spotlight surveys better assessed the distribution and abundance of murrelets in congregations, with 101 and 291 individuals, respectively, observed along the 82-km transect. Highest numbers in 2012 suggest a current breeding population of roughly 100–200 pairs at Catalina, the fourth largest colony in southern California. Congregations were strongly associated with coastal cliffs between (1) Isthmus Cove and Twin Rocks and (2) Iron Bound Bay and Catalina Harbor. In 2000–2013, night-lighting captures of 79 birds in congregations recorded 10 (13%) murrelets with brood patches, usually indicative of egg-laying. During captures in 2008 and spotlight surveys in 2012, three family groups (adults with small downy chicks) departing island nests were observed in nearshore waters. No nests were found during searches on offshore rocks (including Bird Rock) in 1991–1996, but 7 nests were discovered in 2012–2013 during searches of boataccessible shoreline cliffs between Isthmus Cove and Twin Rocks. Overall, 6 of 8 clutches (75%) with known fates were successful, but evidence of mammalian predators preying on murrelet eggs was also present. A long-term monitoring, research, and restoration program is needed at Catalina. Initial restoration efforts should focus on reducing predation by introduced mammals and reducing impacts from oil pollution and bright lights.

An Agent-Based Model of Santa Cruz Island Foxes (Urocyon littoralis santacruzae) which Exhibits an Allee Effect

An Agent-Based Model of Santa Cruz Island Foxes (Urocyon littoralis santacruzae) which Exhibits an Allee Effect

An Agent-Based Model of Santa Cruz Island Foxes (Urocyon littoralis santacruzae) which Exhibits an Allee Effect

In the early 1990s, the island of Santa Cruz off the coast of California experienced a rapid decline of the canid Urocyon littoralis santacruzae. The reasons behind this decline included disease, predation, competition with other species, and genetic bottlenecking. We present an individual-based model that simulates the population of Santa Cruz island foxes. Through our model we provide evidence of the Allee effect in the Santa Cruz island fox population which is exacerbated by selection for reduced reproductive probability.

Social relationships and reproductive behavior of island foxes inferred from proximity logger data

The social behavior of the smaller fox species is poorly known compared with that of larger and more gregarious canids that can be directly observed. We studied social relationships and reproductive behavior of island foxes (Urocyon littoralis) on San Clemente Island (SCI) and San Miguel Island (SMI), off the coast of Southern California, using proximity logging collars. On both islands, pair members interacted more frequently and spent more time together than other types of dyads. On SCI, a high contact rate identified the same 10 mated pairs that were identified by a high degree of home-range overlap. A high contact rate also identified 3 mated pairs on SMI, 2 of which were associated with large pups 9–10 months old. On SMI, the number of contacts and amount of time that mates spent together per day varied across months and peaked in February, when most conceptions occur. Mates spent much less time together in April to June, the pup-rearing season. More unpaired male–female and male–male dyads interacted during January and February than in subsequent months. Paired males appeared to guard their mate during the period when she was receptive. The average duration of estrus was approximately 40 h. Paired females were in contact with other males in addition to their mate near the time they were presumably in estrus, and paired males were in contact with other females in addition to their mate. The relatively short duration of estrus, combined with asynchrony of estrus among females, enabled paired males to leave their mate and seek extrapair copulations without risk of cuckoldry. Proximity logging collars provide a new opportunity to learn about these temporal aspects of social and reproductive behavior in canids.

Effect of anthropogenically developed areas on spatial distribution of island foxes

Virtually no information exists on the impacts of urban areas on island endemics. We examined the spatial distribution of island foxes (Urocyon littoralis clementae) associated with 3 small anthropogenically developed (i.e., “urban”) areas and nonurban areas on San Clemente Island, California. Annual home range size averaged 0.84 km2 (n = 25, SE = 0.07). Our top model indicated that foxes that spent a greater proportion of time in urban areas had significantly smaller home ranges (βPUrb = −0.009, 95% confidence interval [CI] = −0.0180–−0.0002). We found no effect of sex (βSex = 0.0135, 95% CI = −0.1430–0.1700), age (βAge = 0.0502, 95% CI = −0.2730–0.3734), or whether or not a fox was considered a “road” fox (βRoad = −0.0063, 95% CI = −0.2638–0.2513) on home range size. We noted considerable overlap of home ranges of foxes that used urban areas. Foxes used urban areas a greater proportion of time during the night than during the day (t24 = −6.13, P < 0.001); however, foxes did not spend a greater proportion of time in urban areas than expected overall (t24 = −0.59, P = 0.560). We observed 13 of 25 (52%) foxes that utilized urban areas feeding on anthropogenic food resources. Foxes that used urban areas were heavier (n = 35, X̄ = 1.98, SE = 0.05) than foxes that did not use urban areas (n = 26, X̄ = 1.81, SE = 0.04; t59 = −2.69, P = 0.009). Our study is the first to demonstrate the effects urban areas on islands may have on canid populations. Our findings were similar to those reported for urban canid populations on the mainland, suggesting that future conservation and management of carnivores on islands may benefit from strategies that have been successful with mainland species.

Capture success higher near roads for san clemente island foxes

Recently, island fox (Urocyon littoralis) populations on 4 of 6 California Channel Islands (USA) were greatly reduced by colonizing golden eagles (Aquila chrysaetos) and a suspected outbreak of disease, creating concern for subspecies on all islands. Consequently, efforts of live-trapping foxes for research, monitoring, and vaccination has increased. Despite increased trapping efforts, evaluation of factors that influence capture success has not been conducted. We examined capture success of island foxes at 85 random trapping locations on San Clemente Island during 170 trap-nights during 2006–2007. We captured 98 island foxes, and found that traps placed ≤10 m from primary roads had higher overall capture success (i.e., 1.52 times more likely to capture foxes) than traps placed at random locations throughout the study area. We found no evidence to suggest that the density of edges between land-cover types (i.e., sum length of edges per 100-m buffered area [m/m2]), nightly temperature, proportions of land-cover, or type of attractant tested (n = 3) affected capture success. All attractants captured similar proportions of sex and age classes of foxes. Our findings suggest that future trapping efforts would have the most success if conducted along roads. © 2013 The Wildlife Society.

Using Population Viability Criteria to Assess Strategies to Minimize Disease Threats for an Endangered Carnivore

Outbreaks of infectious disease represent serious threats to the viability of many vertebrate populations, but few studies have included quantitative evaluations of alternative approaches to the management of disease. The most prevalent management approach is monitoring for and rapid response to an epizootic. An alternative is vaccination of a subset of the free-living population (i.e., a "vaccinated core") such that some individuals are partially or fully immune in the event of an epizootic. We developed a simulation model describing epizootic dynamics, which we then embedded in a demographic simulation to assess these alternative approaches to managing rabies epizootics in the island fox (Urocyon littoralis), a species composed of only 6 small populations on the California Channel Islands. Although the monitor and respond approach was superior to the vaccinated-core approach for some transmission models and parameter values, this type of reactive management did not protect the population from rabies under many disease-transmission assumptions. In contrast, a logistically feasible program of prophylactic vaccination for part of the wild population yielded low extinction probabilities across all likely disease-transmission scenarios, even with recurrent disease introductions. Our use of a single metric of successful management-probability of extreme endangerment (i.e., quasi extinction)-to compare very different management approaches allowed an objective assessment of alternative strategies for controlling the threats posed by infectious disease outbreaks.

Does litter size variation affect models of terrestrial carnivore extinction risk and management?

BackgroundIndividual variation in both survival and reproduction has the potential to influence extinction risk. Especially for rare or threatened species, reliable population models should adequately incorporate demographic uncertainty. Here, we focus on an important form of demographic stochasticity: variation in litter sizes. We use terrestrial carnivores as an example taxon, as they are frequently threatened or of economic importance. Since data on intraspecific litter size variation are often sparse, it is unclear what probability distribution should be used to describe the pattern of litter size variation for multiparous carnivores.Methodology/Principal FindingsWe used litter size data on 32 terrestrial carnivore species to test the fit of 12 probability distributions. The influence of these distributions on quasi-extinction probabilities and the probability of successful disease control was then examined for three canid species – the island fox Urocyon littoralis, the red fox Vulpes vulpes, and the African wild dog Lycaon pictus. Best fitting probability distributions differed among the carnivores examined. However, the discretised normal distribution provided the best fit for the majority of species, because variation among litter-sizes was often small. Importantly, however, the outcomes of demographic models were generally robust to the distribution used.Conclusion/SignificanceThese results provide reassurance for those using demographic modelling for the management of less studied carnivores in which litter size variation is estimated using data from species with similar reproductive attributes.

Factors influencing reproductive success and litter size in captive island foxes

AbstractA severe decline of island foxes (Urocyon littoralis) on the northern Channel Islands in the 1990s prompted the National Park Service to begin a captive breeding program to increase their numbers. Using detailed records of all the fox pairs (N = 267) that were part of the program on San Miguel, Santa Rosa, and Santa Cruz Islands from its inception in 2000 through 2007, we identified factors influencing the breeding success of pairs in captivity in the interest of formulating strategies that could increase captive productivity. We compiled a database of variables including litter size, reproductive success, distance to nearest occupied pen during the breeding season, subspecies, exposure, female age, male age, age difference, female and male origin (wild vs. captive born), same versus different origin, years paired, previous reproductive success by the pair, previous reproductive success by the female, mate aggression‐related injuries, male previous involvement in a pair with mate aggression, and female previous involvement in a pair with mate aggression. We used multiple linear regression to identify factors predictive of litter size, and logistic regression to predict the probability of reproductive success. A larger inter‐pen distance, older male age, less exposure, and a smaller intra‐pair age difference positively affected litter size. The probabilities of reproductive success increased with fewer years paired and less exposure. Comparatively, pairs with wild born females (vs. captive born females), and previously successful pairs (vs. previously unsuccessful and new pairs) were most likely to be successful. These results indicate that the optimal situation was to pair wild‐caught females with older males in sheltered pens that were as far from other pens as possible, to maintain successful pairs and repair unsuccessful ones. Published 2013. This article is a U.S. Government work and is in the public domain in the USA.

Endemism in host–parasite interactions among island populations of an endangered species

AbstractAimImplicit in conserving interactions is the idea that species behave differently throughout their range, resulting in functionally dissimilar populations of the same species. Host–parasite interactions are a useful system to explore the pervasiveness of these ecological phenotypes. Here, we investigated whether the role of an endangered, endemic species to provide habitat for ectoparasites varies throughout the geographic distribution of the host.LocationChannel Islands, California.MethodsWe captured island foxes (Urocyon littoralis sp.) from three populations: Santa Catalina (n = 72), Santa Rosa (n = 79) and San Miguel (n = 83). We compared the extent to which variation in parasite attributes were due to differences among individuals or populations. As a measure of the latter, we used discriminant function analysis to determine whether individuals from the same population ‘cluster’ together when comparing patterns of intensity in various ectoparasites.ResultsWe identified eight ectoparasite species that included at least six new parasite records for island foxes. We found that ectoparasite attributes including diversity and intensity varied among host populations. More importantly, we show that knowing the parasite composition of the host can identify its population of origin, due to unique host–parasite interactions. Overall, we correctly ‘assigned’ 72% of island foxes to their actual, respective populations, although there were inconsistencies among populations.Main conclusionsIf foxes generally have the same parasite assemblage regardless of their respective populations, then conservation of a single population likely maintains all necessary species interactions and discriminate function analysis is uninformative in discerning population assignments of individuals. Our findings highlight the importance of conserving populations to maintain endemic interactions and caution against extrapolating the ecology (i.e. known species associations) of a species to other locations within their range.

Conservation Strategies for Species Affected by Apparent Competition

Apparent competition is an indirect interaction between 2 or more prey species through a shared predator, and it is increasingly recognized as a mechanism of the decline and extinction of many species. Through case studies, we evaluated the effectiveness of 4 management strategies for species affected by apparent competition: predator control, reduction in the abundances of alternate prey, simultaneous control of predators and alternate prey, and no active management of predators or alternate prey. Solely reducing predator abundances rapidly increased abundances of alternate and rare prey, but observed increases are likely short-lived due to fast increases in predator abundance following the cessation of control efforts. Substantial reductions of an abundant alternate prey resulted in increased predation on endangered huemul (Hippocamelus bisulcus) deer in Chilean Patagonia, which highlights potential risks associated with solely reducing alternate prey species. Simultaneous removal of predators and alternate prey increased survival of island foxes (Urocyon littoralis) in California (U.S.A.) above a threshold required for population recovery. In the absence of active management, populations of rare woodland caribou (Rangifer tarandus caribou) continued to decline in British Columbia, Canada. On the basis of the cases we examined, we suggest the simultaneous control of predators and alternate prey is the management strategy most likely to increase abundances and probabilities of persistence of rare prey over the long term. Knowing the mechanisms driving changes in species' abundances before implementing any management intervention is critical. We suggest scientists can best contribute to the conservation of species affected by apparent competition by clearly communicating the biological and demographic forces at play to policy makers responsible for the implementation of proposed management actions.

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.

Reproductive Ecology and Characteristics of Denning Sites of the San Clemente Island Fox

We monitored movements of 27 radiocollared females of the San Clemente Island fox (Urocyon littoralis clementae) during 2007 to determine the proportion that produced litters, number of offspring in weaned litters, chronology of reproduction, and characteristics of denning sites. Of 23 females, three or four produced a total of six pups. Of 13 recaptured and examined for reproductive status, most had lactated in previous years (n = 7) or had some evidence of lactating but not weaning pups (n = 4); two females had never lactated. Breeding and parturition occurred 2 months earlier than reported for other subspecies of island foxes in wild-born or captive-breeding populations since the 1970s. Females used two or three dens in succession and dens were almost exclusively in rock crevices. Five of 23 foxes had home ranges that included sources of supplemental food and human habitation, including all four females observed with pups, suggesting this could be a factor in reproductive success.Seguimos los movimientos de 27 hembras del zorros isleños (Urocyon littoralis clementae) con collares de radiotransmisores en el 2007 para determinar la proporción de las que parieron, el número de crías destetadas, la cronología de la reproducción, y las características de las madrigueras. Solamente tres o cuatro de las 23 hembras parieron un total de seis cachorros. De las 13 hembras que fueron recapturadas y examinadas para determinar su estado reproductor, la mayoría había lactado en años previos (n = 7) o mostraban evidencia de lactancia pero no de cachorros destetados (n = 4); y dos hembras no habían lactado. Apareamientos y partos ocurrieron 2 meses antes de lo reportado previamente para otras poblaciones de subespecies de zorros isleños de poblaciones silvestres o en cautiverio desde la década de los 1970. Las hembras usaron dos o tres madrigueras en sucesión y estas fueron situadas casi exclusivamente en grietas rocosas. Cinco de las 23 zorras tuvieron rangos de hogar que incluían fuentes de alimentos suplementarios y asentamientos humanos, incluyendo las cuatro hembras con cachorros, sugiriendo que esto puede ser un factor para el éxito reproductivo.

Impact of historical founder effects and a recent bottleneck on MHC variability in Commander Arctic foxes (Vulpes lagopus).

Populations of Arctic foxes (Vulpes lagopus) have been isolated on two of the Commander Islands (Bering and Mednyi) from the circumpolar distributed mainland population since the Pleistocene. In 1970–1980, an epizootic outbreak of mange caused a severe population decline on Mednyi Island. Genes of the major histocompatibility complex (MHC) play a primary role in infectious disease resistance. The main objectives of our study were to compare contemporary variation of MHC class II in mainland and island Arctic foxes, and to document the effects of the isolation and the recent bottleneck on MHC polymorphism by analyzing samples from historical and contemporary Arctic foxes. In 184 individuals, we found 25 unique MHC class II DRB and DQB alleles, and identified evidence of balancing selection maintaining allelic lineages over time at both loci. Twenty different MHC alleles were observed in mainland foxes and eight in Bering Island foxes. The historical Mednyi population contained five alleles and all contemporary individuals were monomorphic at both DRB and DQB. Our data indicate that despite positive and diversifying selection leading to elevated rates of amino acid replacement in functionally important antigen-binding sites, below a certain population size, balancing selection may not be strong enough to maintain genetic diversity in functionally important genes. This may have important fitness consequences and might explain the high pathogen susceptibility in some island populations. This is the first study that compares MHC diversity before and after a bottleneck in a wild canid population using DNA from museum samples.

Reproduction and denning by urban and rural San Clemente Island foxes (Urocyon littoralis clementae)

Island foxes ( Urocyon littoralis (Baird, 1858)) have experienced severe reductions in populations on 4 out of 6 California Channel Islands. Although numbers of foxes on San Clemente Island (SCLI; Urocyon littoralis clementae Merriam, 1903) have remained relatively stable, data on reproductive success in urban and rural areas are necessary to better understand population dynamics of foxes and manage the population if it sustains declines. Determining locations and characteristics of den sites will also assist in minimizing possible impacts of humans on foxes. We found that 10 female foxes produced at least 19 kits during 2008. Female foxes that spent a greater proportion of time within an urban area had greater probability of reproducing compared with foxes that infrequently utilized urban areas. However, these “urban” foxes often selected den sites nearer to roads, which may expose them to increased mortalities. We located 23 den sites on a mean of 17°–18° slopes with 40% having westerly facing aspects. We recommend avoiding human disturbance to these areas from February through June, which may minimize potential impacts on foxes. Our study should provide insight into managing island foxes, especially in respect to urban areas on other Channel Islands.

Effects of roads on survival of San Clemente Island foxes

AbstractRoads generate a variety of influences on wildlife populations; however, little is known about the effects of roads on endemic wildlife on islands. Specifically, road‐kills of island foxes (Urocyon littoralis) on San Clemente Island (SCI), Channel Islands, California, USA are a concern for resource managers. To determine the effects of roads on island foxes, we radiocollared foxes using a 3‐tiered sampling design to represent the entire population in the study area, a sub‐population near roads, and a sub‐population away from roads on SCI. We examined annual survival rates using nest‐survival models, causes of mortalities, and movements for each sample. We found the population had high annual survival (0.90), although survival declined with use of road habitat, particularly for intermediate‐aged foxes. Foxes living near roads suffered lower annual survival (0.76), resulting from high frequencies of road‐kills (7 of 11 mortalities). Foxes living away from roads had the highest annual survival (0.97). Road‐kill was the most prominent cause of mortality detected on SCI, which we estimated as killing 3–8% of the population in the study area annually. Based on movements, we were unable to detect any responses by foxes that minimized their risks from roads. The probabilities of road‐kills increased with use of the road habitat, volume of traffic, and decreasing road sinuosity. We recommend that managers should attempt to reduce road‐kills by deterring or excluding foxes from entering roads, and attempting to modify behaviors of motorists to be vigilant for foxes. © 2011 The Wildlife Society.