Reducing the impacts of leg hold trapping on critically endangered foxes by modified traps and conditioned trap aversion on San Nicolas Island, California, USA

Padded leg-hold live traps were used as the primary removal technique in the successful eradication of feral cats Felis silvestris catus from San Nicolas Island, California, USA. Risk of injury to endemic San Nicolas Island foxes Urocyon littoralis dickeyi, a similarly sized and more abundant non-target species, was mitigated by using a smaller trap size, modifying the trap and trap set to reduce injuries, and utilising a trap monitoring system to reduce time animals spent in traps. Impacts to foxes during the eradication campaign were further reduced by having a mobile veterinary hospital on island to treat injured foxes. Compared to other reported fox trapping efforts, serious injuries were reduced 2-7 times. Trapping efforts exceeded animal welfare standards, with 95% of fox captures resulting in minor or no injuries. Older foxes were more likely to receive serious injury. Fox captures were also reduced through aversive conditioning, with initial capture events providing a negative stimulus to prevent recaptures. Fox capture rates decreased up to six times during seven months of trapping, increasing trap availability for cats, and improving the efficacy of the cat eradication program. No aspect of the first capture event was significantly linked to the chance of recapture

Estimates of Energy and Prey Requirements of Wolverines

Wolverine (Gulo gulo) populations have decreased throughout much of their North American range and there is interest in establishing recovery programs in the Sierra Nevada of California and the Rocky Mountains of Colorado. Determining the sufficiency of prey resources is an important consideration for initiating wolverine recovery, yet there are limited data on resource availability and needs. Our goal is to estimate prey requirements based on wolverine caloric needs and the caloric content of prey likely to be available. We achieve this goal by modifying existing models to account for wolverine biology. Models show a male wolverine requires 5096 kJ/day (2925-7462 kJ) and a female wolverine requires 3645 kJ/day (2158-5439 kJ). This translates to an annual energy budget for males of 1.9 million kJ/yr that could be met by consuming the equivalent of approximately 8 mule deer/yr (Odocoileus hemionus) and 1.4 million kJ/yr for females that could be met by consuming the equivalent of less than 6 mule deer/yr. In light of published records of prey availability, these results suggest populations of wolverines could be sustained where recovery programs are being considered in Colorado and California. We suggest incorporating energetic needs of focal species, such as those calculated here for wolverines, into the assessment of resource availability before implementing recovery programs. Further, these estimates can be applied to management and conservation of wolverines throughtout their range

Pathology and Epidemiology of Ceruminous Gland Tumors among Endangered Santa Catalina Island Foxes (Urocyon littoralis catalinae) in the Channel Islands, USA

In this study, we examined the prevalence, pathology, and epidemiology of tumors in free-ranging island foxes occurring on three islands in the California Channel Islands, USA. We found a remarkably high prevalence of ceruminous gland tumors in endangered foxes (Urocyon littoralis catalinae) occurring on Santa Catalina Island (SCA)--48.9% of the dead foxes examined from 2001-2008 had tumors in their ears, and tumors were found in 52.2% of randomly-selected mature (≥ 4 years) foxes captured in 2007-2008, representing one of the highest prevalences of tumors ever documented in a wildlife population. In contrast, no tumors were detected in foxes from San Nicolas Island or San Clemente Island, although ear mites (Otodectes cynotis), a predisposing factor for ceruminous gland tumors in dogs and cats, were highly prevalent on all three islands. On SCA, otitis externa secondary to ear mite infection was highly correlated with ceruminous gland hyperplasia (CGH), and tumors were significantly associated with the severity of CGH, ceruminous gland dysplasia, and age group (older foxes). We propose a conceptual model for the formation of ceruminous gland tumors in foxes on SCA that is based on persistent, ubiquitous infection with ear mites, and an innate, over exuberant inflammatory and hyperplastic response of SCA foxes to these mites. Foxes on SCA are now opportunistically treated with acaricides in an attempt to reduce mite infections and the morbidity and mortality associated with this highly prevalent tumor

Serologic survey of the island spotted skunk on Santa Cruz Island

Two rare endemic carnivores occur on California\u27s northern Channel Islands: island spotted skunks (Spilogale gracilis amphiala) and island foxes (Urocyon littoralis). As insular carnivores, both may be particularly vulnerable to novel pathogens. We tested sera from 31 island spotted skunks on Santa Cruz Island, where both skunks and foxes occur sympatrically, to establish their exposure to disease agents. One skunk (3%) tested positive for canine heartworm, and 3 skunks (10%) tested positive for canine parvovirus. None showed evidence of exposure to canine adenovirus, canine distemper virus, canine herpesvirus, Leptospira bacteria (serovars pomona, canicola, and icterohaemorrhagiae), or pseudorabies virus. Spotted skunks on Santa Cruz Island apparently have low susceptibility or exposure to these pathogens and are unlikely to be reservoirs of these diseases for island foxes

Evaluation of the effects of multiple capture methods and immobilization drugs on mountain lion welfare

Using a dataset of 591 capture events between 2001–2019 in California, USA, we examined the impact of capture methods and immobilization drugs on mountain lion (Puma concolor) welfare. The 3 methods used to capture mountain lions were cage traps, trained hounds, and cable restraints. The drugs used to immobilize mountain lions were either tiletamine/zolazepam (Telazol®), ketamine/medetomidine, or ketamine/xylazine. Mortality occurred in 1.4% of captures, with only one mortality out of 310 captures occurring since 2012. We used a logistic regression framework to compare morbidity and vital parameters of mountain lions among the different capture methods and immobilization drugs used. Vomiting (a risk factor for developing aspiration pneumonia) was the most common severe risk factor associated with cage trapping and was only seen with the use of ketamine/medetomidine or ketamine/xylazine. Morbidity scores were not well predicted by any of the variables we accounted for. Animals immobilized with Telazol® were more likely to experience abnormal heart and respiratory rates, as well as high body temperatures, than those immobilized with the other two combinations. Although there are risks associated with each of the capture methods and drug combinations commonly used in mountain lion captures in California, our analyses demonstrated they are all relatively safe when following appropriate animal welfare practices. Our analyses suggested that unaccounted for factors are equally or more important in explaining injury and physiological abnormality rates, and we urge that agencies train personnel in best practices and conservative decision-making in order to assure that the welfare of the animal takes precedence over collaring. We suggest training on how to choose between several capture techniques, immobilization drugs and monitoring methods and how to reduce both detrimental effects to mountain lions and danger to humans

A Functional Response in Resource Selection Links Multiscale Responses of a Large Carnivore to Human Mortality Risk

Theory suggests that animals make hierarchical, multiscale resource selection decisions to address the hierarchy of factors limiting their fitness. Ecologists have developed tools to link population-level resource selection across scales; yet, theoretical expectations about the relationship between coarse- and fine-scale selection decisions at the individual level remain elusive despite their importance to fitness. With GPS-telemetry data collected across California, USA, we evaluated resource selection of mountain lions (Puma concolor; n = 244) relative to spatial variation in human-caused mortality risk. With hierarchical resource selection, coarse-scale selection determines availability at finer scales. This simple relationship allowed us to demonstrate that functional responses in resource selection explicitly link individual-level resource selection decisions across scales. We show that individuals proactively avoiding risk when selecting home ranges are freed to relax this avoidance when making decisions within home ranges. However, individuals also exhibit reactive avoidance of risk at the finest scales along movement paths.</p

Adaptive divergence despite strong genetic drift: genomic analysis of the evolutionary mechanisms causing genetic differentiation in the island fox (\u3ci\u3eUrocyon littoralis\u3c/i\u3e)

The evolutionary mechanisms generating the tremendous biodiversity of islands have long fascinated evolutionary biologists. Genetic drift and divergent selection are pre- dicted to be strong on islands and both could drive population divergence and specia- tion. 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 Chan- nel Island. Analysis of 5293 SNP loci generated using Restriction-site Associated DNA (RAD) sequencing found support for genetic drift as the dominant evolutionary mech- anism driving population divergence among island fox populations. In particular, pop- ulations 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

The ecology of human-caused mortality for a protected large carnivore

Mitigating human-caused mortality for large carnivores is a pressing global challenge for wildlife conservation. However, mortality is almost exclusively studied at local (within-population) scales creating a mismatch between our understanding of risk and the spatial extent most relevant to conservation and management of wide-ranging species. Here, we quantified mortality for 590 radio-collared mountain lions statewide across their distribution in California to identify drivers of human-caused mortality and investigate whether human-caused mortality is additive or compensatory. Human-caused mortality, primarily from conflict management and vehicles, exceeded natural mortality despite mountain lions being protected from hunting. Our data indicate that human-caused mortality is additive to natural mortality as population-level survival decreased as a function of increasing human-caused mortality and natural mortality did not decrease with increased human-caused mortality. Mortality risk increased for mountain lions closer to rural development and decreased in areas with higher proportions of citizens voting to support environmental initiatives. Thus, the presence of human infrastructure and variation in the mindset of humans sharing landscapes with mountain lions appear to be primary drivers of risk. We show that human-caused mortality can reduce population-level survival of large carnivores across large spatial scales, even when they are protected from hunting

The reintroduction of bald eagles on Santa Catalina Island, California

In 1980 a program was initiated to reintroduce bald eagles (Haliaeetus leucocephalus) to the California Channel Islands. Bald eagles were historically found on all of the islands, and were numerous on the larger islands. From 1980 through 1984, 20 eagles were translocated to Santa Catalina Island and reared on hacking platforms until released. All released birds returned to the platforms to feed. Early flights by the birds were comparable to other reintroduction programs and to wild reared eagles. The eagles subsisted on food provided by the investigators for up to seven weeks of age. There were seven known cases of mortality. Causes of mortality included shooting, electrocution on high power lines, and intraspecific aggression. Birds in the first, second, and third year age classes, all used available habitats significantly different than expected from random (P 0.05). Birds in their first year used only the chaparral differently than expected between seasons. Habitats used differently than expected between seasons for second and third year birds were relict coastal sage, oak woodland and relict oak woodland (second year birds); relict oak woodland and grassland (third year birds). Availability of carrion during the fall and winter hunting seasons may effect the distribution of the eagles on the island. Female eagles were significantly more successful (P = 0.001) in supplanting male eagles from carcasses and perches. Females were 100 percent successful in supplanting same aged males. Males of the same age only attempted to supplant females in 21 percent of the interactions (n = 58) and were successful in 42 percent of their attempts. Age does not appear to play as important of a role as sex in determining the outcome of supplanting attempts