The evolutionary mechanisms generating the tremendous biodiversity of islands have long fascinated evolutionary biologists. Genetic drift and divergent selection are predicted to be strong on islands ...and both could drive population divergence and speciation. Alternatively, strong genetic drift may preclude adaptation. We conducted a genomic analysis to test the roles of genetic drift and divergent selection in causing genetic differentiation among populations of the island fox (Urocyon littoralis). This species consists of six subspecies, each of which occupies a different California Channel Island. Analysis of 5293 SNP loci generated using Restriction‐site Associated DNA (RAD) sequencing found support for genetic drift as the dominant evolutionary mechanism driving population divergence among island fox populations. In particular, populations had exceptionally low genetic variation, small Nₑ (range = 2.1–89.7; median = 19.4), and significant genetic signatures of bottlenecks. Moreover, islands with the lowest genetic variation (and, by inference, the strongest historical genetic drift) were most genetically differentiated from mainland grey foxes, and vice versa, indicating genetic drift drives genome‐wide divergence. Nonetheless, outlier tests identified 3.6–6.6% of loci as high FST outliers, suggesting that despite strong genetic drift, divergent selection contributes to population divergence. Patterns of similarity among populations based on high FST outliers mirrored patterns based on morphology, providing additional evidence that outliers reflect adaptive divergence. Extremely low genetic variation and small Nₑ in some island fox populations, particularly on San Nicolas Island, suggest that they may be vulnerable to fixation of deleterious alleles, decreased fitness and reduced adaptive potential.
Disease, predation, and genetic isolation resulted in 4 of 6 island fox (Urocyon littoralis) subspecies being listed as endangered in 2004. Potential for disease outbreaks continues to pose a major ...threat to the persistence of these isolated, endemic populations. We examined how roads influence the spatial ecology of San Clemente Island foxes (U. l. clementae), particularly in regard to spread of disease, to provide management recommendations for preventing or minimizing a disease outbreak on San Clemente Island, California, USA. Home range areas (x̄ = 0.75 km²) and core areas (x̄ = 0.19 km²) of foxes on San Clemente Island were 0.36–1.23 and 2.17 times larger, respectively, than estimates from Santa Cruz Island foxes (U. l. santacruzae). Home ranges and core areas were 78% larger and 73% larger, respectively, for foxes near roads than for foxes away from roads. Home ranges were also largest when foxes were not caring for offspring (i.e., seasons of pup-independence and breeding). We did not detect any dispersal movements, but foxes living near roads moved 33% farther in 2-hour periods than foxes not living near roads. Foxes near roads move faster, range more widely, and could more rapidly spread a pathogen throughout the island; therefore, roads might serve as transmission corridors. We recommend reducing this risk by increasing widths of vaccination firewalls (areas where vaccination is used to induce a disease-resistant or immune population of foxes), ensuring these areas deliberately intersect roads, and vaccinating a higher proportion of foxes living near roads. Disease risk models incorporating these strategies could inform the lowest risk scenarios.
Channel Island foxes (Urocyon littoralis) live on six of the eight California Channel Islands, and each island is inhabited by a distinct subspecies. Until recently, four of these subspecies were ...listed under the Endangered Species Act as endangered. Although three of the four subspecies have been delisted, and one subspecies was downlisted to threatened, all subspecies are still vulnerable because of small population sizes and potential threats from predation and disease. Consequently, information on reproductive behavior for each subspecies, including the San Clemente Island fox (Urocyon littoralis clementae), is important for understanding fox population dynamics. We determined reproductive status of 28 island foxes through observations of radio collared yearlings and adults with or without juveniles between 25 February and 8 October 2009. We found a greater number of adult foxes than yearling foxes and a greater number of female foxes than male foxes observed with juveniles. Also, there was a significantly greater probability of observing adult female foxes with juveniles than yearling males with juveniles. Only 1 of 28 radio collared foxes exhibited either polygamous or “helper” behaviors. Parturition started approximately 2 months earlier than historically recorded for other Channel Island fox subspecies. Our results suggest that in future studies of reproductive success more effort should be placed on monitoring adult females than yearling males. If emergence from dens continues to occur earlier than previously recorded, the current recommended time period for trapping (20 June–31 January) might need revision to exclude January to reduce stress to pregnant females. If all foxes have similar probabilities of transmitting disease on a given contact with juveniles, our data suggest that it may be appropriate to focus more vaccination efforts on females than males and adults than yearlings because they contact juveniles more frequently.
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.
The potential role of rock pigeons (Columba livia) in the epidemiology of shiga toxin– producing Escherichia coli (STEC) and Salmonella enterica is unclear. Our objective was to determine the ...prevalence of STEC and S. enterica in pigeons at urban and dairy settings as a function of season. Prevalence of STEC and S. enterica was estimated by bacteriologic culture of cloacal swabs collected from pigeons trapped at urban and dairy locations in and around Fort Collins, Colorado from January to November 2003. Presumptive E. coli isolates were tested for the presence of virulence genes SLT-1, SLT-2, eae, hlyA, K1, CNF-1, CNF-2, and LT using polymerase chain reaction. Shiga toxins were not isolated from any of 406 samples from pigeons, but virulence genes typically associated with disease in humans were identified in isolates from 7.9% (95% CI: 5.5% to 10.9%) of captured pigeons. S. enterica were detected in 3.2% of 277 samples from pigeons, with all positive samples originating from dairy locations (nine of 106 8.5%; 95% CI: 4.0–15.5%). The results suggest that although pigeons may acquire S. enterica from cattle and play a role in recirculation and persistence of the microorganism at dairies, pigeons are not important carriers of STEC.
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.
Because coyotes (Canis latrans) show an aversion to novel objects, we examined the effects of the presence and removal of repellent and attractive stimuli on coyote behavior. We found a greater ...proportion of captive coyotes investigated 10-cm-tall cones (0.95) compared to 90-cm-tall cones (0.68) and control sites (0.81), and spent longer periods (P < 0.001 in all instances) investigating small cones (𝑥̄ = 465 sec), compared to large cones (𝑥̄ = 212 sec) and control sites (𝑥̄ = 45 sec). However, investigation times at sites following removal of large cones were 1.6 and 2.3 times greater than investigation times at sites following removal of small cones and the control, respectively. Results from pen studies were supported by a field study. Wild coyotes in south Texas visited 43% of small cones but did not visit large cones. Following removal of cones, visits to small cone stations decreased to 29%, whereas coyotes visited 43% of large cone stations. Thus, we observed a direct relationship between aversion toward large novel objects and subsequent attraction to sites following their removal among both captive and wild coyotes. Based upon our results, we suggest that placing large novel objects over traps that are set and removing such objects after a few days, with the subsequent addition of an olfactory attractant, may increase exploratory behavior and capture of coyotes.
Woodpeckers cause severe damage to utility poles and crossarms, resulting in substantial economic losses to utility companies. We evaluated effectiveness of a polyurea elastomer coating material for ...reducing damage by captive pileated woodpeckers (Dryocopus pileatus) to utility pole crossarms. Because woodpeckers inflicted essentially no damage to the fully coated crossarms, we infer that the coating material holds substantial promise for protecting utility pole crossarms. Additional research should be conducted to evaluate the coating under field conditions.
Mule deer (Odocoileus hemionus) fawn:doe (f:d) ratios in December have declined by 0.015 fawns/doe/year from 1972 through 1995 in Colorado, USA. To determine whether lower pregnancy or fetal ...production was the cause of low December f:d ratios, we estimated mule deer pregnancy rates in the Poudre River drainage during January 1998 and pregnancy and fetal rates on the Uncompahgre Plateau during February 1999. Twenty-seven (93.1%) of 29 yearling and adult does in the Poudre River drainage were detected pregnant with pregnancy-specific protein-B (PSPB). This proportion did not differ (P > 0.2) from the proportion of yearling and adult does that were pregnant when collected by various methods in previous studies in Colorado. Thirty-six (90%) of 40 adult does were detected pregnant with PSPB, and 37 (93%) of these 40 does on the Uncompahgre Plateau were detected pregnant with ultrasound. Proportion of adult does detected pregnant with ultrasound did not differ (P > 0.07) from pregnancy rate of adult does collected by various methods in previous studies. Average number of fetuses per doe for all adult does (pregnant and nonpregnant) on the Uncompahgre Plateau (n = 40, x̄ = 1.70, SE = 0.109) was not less (P > 0.06) than for adult does collected by various methods in previous studies. We concluded that failure to breed or maintain pregnancy through at least early January or early February does not appear to be the cause of low f:d ratios observed in Colorado.
Areas occupied by white-tailed prairie dogs (WTPD; Cynomys leucurus) and Gunnison's prairie dogs (GPD; C. gunnisoni) are not well-known in Colorado (USA) and elsewhere. Suitable methodology for ...monitoring changes in populations of WTPD and GPD over broad areas also has not been well established. We evaluated occupancy modeling methodology to establish baseline occupancy rates for WTPD and GPD in Colorado. We estimated that WTPD occupied 24.1% (SE = 12.8) of 47,710 0.25-km2 plots and GPD occupied 7.5% (SE = 1.3) of 158,225 0.25-km2 plots in Colorado during 2004 and 2005. Areas reported as colonies in the Colorado Division of Wildlife's database were not good predictors of WTPD and GPD occupancy. Occupancy rates were highest for GPD at intermediate elevations. We estimated detection probabilities for surveys from the ground of 0.760 (SE = 0.042) for WTPD and 0.786 (SE = 0.060) for GPD. Probability of detection for WTPD improved with lower temperature and earlier Julian date, whereas no covariates improved detection rates for GPD. We recommend that wildlife managers use occupancy monitoring to establish status and trends in populations of WTPD and GPD across their range.
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