Farmed arctic foxes on the Fennoscandian mountain tundra: implications for conservation

Hybridization between wild and captive-bred individuals is a serious conservation issue that requires measures to prevent negative effects. Such measures are, however, often considered controversial by the public, especially when concerning charismatic species. One of the threats to the critically endangered Fennoscandian arctic fox Alopex lagopus is hybridization with escaped farm foxes, conveying a risk of outbreeding depression through loss of local adaptations to the lemming cycle. In this study, we investigate the existence of escaped farm foxes among wild arctic foxes and whether hybridization has occurred in the wild. We analysed mitochondrial control region sequences and 10 microsatellite loci in samples from free-ranging foxes and compared them with reference samples of known farm foxes and true Fennoscandian arctic foxes. We identified the farm fox specific mitochondrial haplotype H9 in 25 out of 182 samples, 21 of which had been collected within or nearby the wild subpopulation on Hardangervidda in south-western Norway. Genetic analyses of museum specimens collected on Hardangervidda (1897–1975) suggested that farm fox genotypes have recently been introduced to the area. Principal component analysis as well as both model- and frequency-based analyses of microsatellite data imply that the free-ranging H9s were farm foxes rather than wild arctic foxes and that the entire Hardangervidda population consisted of farm foxes or putative hybrids. We strongly recommend removal of farm foxes and hybrids in the wild to prevent genetic pollution of the remaining wild subpopulations of threatened arctic foxes.     

Detection of farm fox and hybrid genotypes among wild arctic foxes in Scandinavia

In Scandinavia, farmed arctic foxes frequently escape from farms, raising concern about hybridization with the endangered wild population. This study was performed to find a genetic marker to distinguish escaped farm foxes from wild Scandinavian foxes. Microsatellite and mitochondrial control region variation were analyzed in 41 farm foxes. The results were compared with mitochondrial and microsatellite data from the wild population in Scandinavia. The farm foxes were genetically distinct from the wild foxes (F _ST=0.254, P < 0.00001) and all farm foxes had a single control region haplotype different from those observed in the wild population. We developed a method based on Restriction Fragment Length Polymorphism (RFLP) on the mitochondrial control region to differentiate between farmed and wild arctic foxes. This test was subsequently successfully used on 25 samples from free-ranging foxes, of which four had a suspected farm origin. All four of the suspected foxes, and none of the others, carried the farm fox haplotype. Three of these were successfully genotyped for all eleven microsatellite loci. A population assignment test and a Bayesian Markov Chain Monte Carlo analysis indicated that two of these individuals were escaped farm foxes, and that the third possibly was a hybrid between a farmed and a wild arctic fox.     

First report of Trichinella nativa in red foxes (Vulpes vulpes schrencki) from Otaru City, Hokkaido, Japan.

Forty-three red foxes (Vulpes vulpes schrencki) and nine raccoon dogs (Nyctereutes procyonoides viverrinus) were captured in Otaru City, Hokkaido, Japan and examined by muscle digestion for the presence of Trichinella sp. larvae. Of the foxes, five (11.6%) were positive for larvae of Trichinella nativa while none of the raccoon dogs were found to be positive. This finding suggests that the red foxes are important reservoir hosts of sylvatic trichinellosis in Otaru, Hokkaido. This is the first report on Trichinella nativa in wild red foxes of Hokkaido, Japan.     

Do wild dogs exclude foxes? Evidence for competition from dietary and spatial overlaps

Abstract The management of wild canids (wild dogs/dingoes and foxes) presents a conservation dilemma for land managers across Australia. These canids are predators of wildlife and domestic stock but dingoes are considered native and anecdotal reports suggest that they may suppress foxes such that dingo/dog conservation may have a net benefit to wildlife. This study examines dietary and spatial interactions between wild dogs and foxes in the Greater Blue Mountains region of NSW to address the possibility of suppression through competitive exclusion by dogs on foxes. Predator diets were compared using faecal analysis as well as an analysis of 19 dietary studies from similar forest habitats in eastern Australia. Spatial relationships were examined using data from an extensive canid control programme. Diets of wild dogs and foxes showed a high degree of overlap in species taken, indicating potential for competition. But there was also evidence of resource partitioning with the size and arboreality of mammalian prey differing between the two predators. Wild dogs and foxes responded to different landscape‐scale variation in the physical environment, but there was no clear evidence of large‐scale differences in their distribution. At the fine scale there was a negative association between these predators that indicated possible temporal avoidance or localized habitat shifts. Therefore, there is evidence for dietary competition and fine‐scale exclusion, but no support for landscape‐scale exclusion of foxes by wild dogs in the Blue Mountains.     

The Fox (Vulpes vulpes) as a Reservoir for Canine Angiostrongylosis in Denmark

Until recently, Angiostrongylus vasorum was not considered to be an endogenous Danish parasite, since demonstration of this worm had been confined to necropsy findings in 2 dogs, both of which had visited France. During the last 2 years, however, clinical cases have been diagnosed among a considerable number of Danish dogs, none of which had ever been outside Denmark. All these cases have occurred north of Copenhagen, where an endemic focus seems to exist. In this field survey A. vasorum was found for the first time in wild Danish red foxes. Furthermore, experimental infections showed that the parasite can be transferred between foxes and dogs. Consequently, the wild fox population must be considered a potential reservoir for transfer of A. vasorum to domestic dogs.     

Survey of antibodies to Trypanosoma cruzi and Leishmania spp. in gray and red fox populations from North Carolina and Virginia

American trypanosomiasis and leishmaniasis are caused by related hemoflagellate parasites, Trypanosoma cruzi and Leishmania spp., which share several common host species. Both zoonotic protozoans are endemic in the United States. Canines, including domestic and wild canids, are reservoir hosts for human infections with T. cruzi and Leishmania spp. The present study examined the seroprevalence of T. cruzi and Leishmania spp. in wild canids from North Carolina and Virginia. Wild canine species tested in this work included 49 gray foxes (Urocyon cinereoargenteus) and 5 red foxes (Vulpes vulpes). Overall, sera samples from 54 foxes (North Carolina = 43; Virginia = 11) were tested by immunochromatographic strip assays (ICT). Antibodies to T. cruzi were found in 4 (9%) gray foxes from North Carolina and 2 (18%) gray foxes from Virginia. Antibodies to Leishmania spp. were detected in 1 (2%) gray fox from North Carolina. Our results indicate that wild canids are exposed more frequently to T. cruzi in North Carolina than Leishmania spp. and only T. cruzi in Virginia.     

Rabies of wild mammals in Russia at the turn of the 20th and 21st centuries

Analysis of the incidence of animal rabies in Russia (1960–2006) and assessment of the abundance of wild canids and rabies infection prevalence among them (1981–2006) have been made. The results provide evidence for the dominant role of red foxes in the spread of rabies among wild animals (91.67%), which is confirmed by a strong correlation between the abundance of this predator and the numbers of infected animals (r = 0.73). In 2004 to 2006, the prevailing incidence of animal rabies in one or another territory was determined mainly (74.7%) by the pooled population density of red and corsac foxes and wolves. Natural and economic features of the landscape determined the incidence of rabies indirectly, via changes in the numbers of wild animals (by 68.9%). A comparative analysis of the recorded and potentially possible rabies incidence rates among wolves, red and corsac foxes, and raccoon dogs over the period from 1996 and 2006 is presented.     

Diets of sympatric native and introduced carnivores in the Barrington Tops,eastern Australia

Invasive predators have severe impacts on global biodiversity, and their effects in Australia have been more extreme than on any other continent. The spotted‐tailed quoll (Dasyurus maculatus), an endangered marsupial carnivore, coexists with three eutherian carnivores, the red fox (Vulpes vulpes), feral cat (Felis catus) and wild dog (Canis lupus ssp.) with which it did not coevolve. No previous study has investigated dietary overlap between quolls and the suite of three eutherian carnivores. By analysing scats, we aimed to quantify dietary overlap within this carnivore assemblage in eastern Australia, and to detect any differences that may facilitate coexistence. We also sought evidence of intraguild predation. Dietary overlap between predators was extensive, with the greatest similarity occurring between foxes and cats. However, some differences were apparent. For example, cats mainly consumed smaller prey, and wild dogs larger prey. Quolls showed greater dietary overlap with foxes and cats than with dogs. Intraguild predation was evident, with fox remains occurring in 3% of wild dog scats. Our results suggest wild dogs competitively dominate invasive foxes, which in turn are likely to compete with the endangered quoll.     

Prevalence of antibodies against canine distemper virus among red foxes in Luxembourg

Canine distemper virus (CDV) has a wide host spectrum, and during the past years, distemper has been observed in species that were previously not considered to be susceptible. In this study, we investigated the prevalence of CDV-specific antibodies in red foxes (Vulpes vulpes) sampled between May and November 1997. About 9 to 13% of the Luxembourg red fox population is positive for antibodies against CDV. Thus a sizeable proportion of red foxes has been exposed to CDV in the wild. The significance of CDV in red foxes is discussed.     

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.     

Interspecific and Geographic Variation in the Diets of Sympatric Carnivores: Dingoes/Wild Dogs and Red Foxes in South-Eastern Australia

Dingoes/wild dogs (Canis dingo/familiaris) and red foxes (Vulpes vulpes) are widespread carnivores in southern Australia and are controlled to reduce predation on domestic livestock and native fauna. We used the occurrence of food items in 5875 dingo/wild dog scats and 11,569 fox scats to evaluate interspecific and geographic differences in the diets of these species within nine regions of Victoria, south-eastern Australia. The nine regions encompass a wide variety of ecosystems. Diet overlap between dingoes/wild dogs and foxes varied among regions, from low to near complete overlap. The diet of foxes was broader than dingoes/wild dogs in all but three regions, with the former usually containing more insects, reptiles and plant material. By contrast, dingoes/wild dogs more regularly consumed larger mammals, supporting the hypothesis that niche partitioning occurs on the basis of mammalian prey size. The key mammalian food items for dingoes/wild dogs across all regions were black wallaby (Wallabia bicolor), brushtail possum species (Trichosurus spp.), common wombat (Vombatus ursinus), sambar deer (Rusa unicolor), cattle (Bos taurus) and European rabbit (Oryctolagus cuniculus). The key mammalian food items for foxes across all regions were European rabbit, sheep (Ovis aries) and house mouse (Mus musculus). Foxes consumed 6.1 times the number of individuals of threatened Critical Weight Range native mammal species than did dingoes/wild dogs. The occurrence of intraguild predation was asymmetrical; dingoes/wild dogs consumed greater biomass of the smaller fox. The substantial geographic variation in diet indicates that dingoes/wild dogs and foxes alter their diet in accordance with changing food availability. We provide checklists of taxa recorded in the diets of dingoes/wild dogs and foxes as a resource for managers and researchers wishing to understand the potential impacts of policy and management decisions on dingoes/wild dogs, foxes and the food resources they interact with.     

Presence of rabies neutralizing antibodies in wild carnivores following an outbreak of bovine rabies.

In an outbreak of bovine rabies in Argentina, a study was made of vampire bats (Desmodus rotundus) and wild carnivores. Rabies antibody rates of high prevalence were found in the bats, foxes (Dusicyon gymnocercus) and skunks (Conepatus chinga). The outbreak was part of an extensive continuing epizootic of vampire transmitted bovine rabies which may have also involved other vectors in the area of this study. Consumption of dead and dying bats by the carnivores is the suggested means of passage of rabies virus from vampire bats to foxes and skunks. Given optimum conditions it is conceivable that some outbreaks in carnivores may begin in this way.     

Echinococcus multilocularis identified in Michigan with additional records from Ohio

Echinococcus multilocularis was identified in a coyote in Indiana in January 1990, prompting an investigation of the distribution and prevalence of the parasite in wild canids in Indiana and surrounding states. In 1990-1991, the parasite was found throughout northern and central Indiana, in northwestern Ohio, and in east-central Illinois. In 1993-1994, 162 wild canids (97 red foxes, 54 coyotes, 11 gray foxes) were collected from Michigan, and an additional 75 (55 red foxes, 7 coyotes, 13 gray foxes) from Ohio, and examined for this parasite. Of these, 15 wild canids (6.3%) were found to be infected with E. multilocularis , including 4 of 97 (4.1%) red foxes from Michigan and 9 of 55 (16.4%) red foxes and 2 of 7 (28.6%) coyotes from Ohio. In Michigan, all infected animals were from the central and southwestern parts of the state. No infected animals were found in northern Michigan, including the Upper Peninsula. In Ohio, infected animals were limited to the northwestern and west-central portions of the state. These findings constitute new state and distribution records for E. multilocularis in the midwestern United States and indicate that the parasite continues to spread eastward and into Michigan from the south.     

The effects of red fox Vulpes vulpes faecal odours on the feeding behaviour of Orkney voles Microtus arvalis

Orkney voles Microtus arvalis show avoidance of red fox Vulpes vulpes faecal odours, both in the laboratory and in the wild. Since these voles have been isolated from foxes since Neolithic times it is likely that these responses are innate rather than learned.
When applied to young Scots pine saplings, the fox odour inhibited feeding by voles when alternative foods were available.     

Sylvatic trichinellosis in southwestern Spain

The epidemiology of Trichinella spp. in their main sylvatic hosts, wild boar (Sus scrofa ferus and red fox (Vulpes vulpes), in Extremadura (southwestern Spain) was studied. We examined 88 Trichinella spp.-positive wild boar muscle-tissue samples from a total of 29,333 killed animals, referred to the Veterinary Parasitology Department (University of Extremadura, Spain) by the Extremadura Veterinary Service. Additionally, 227 red foxes killed during the hunting season and thus not subject to veterinary controls were examined for trichinellosis. Trichinella spp. larvae were found in six (3%) of the red foxes. All samples were examined using direct diagnostic techniques, including trichinoscopy and artificial digestion. The mean intensity of infection was 74.8 larvae/g (LPG) of muscle tissue in wild boars, compared to 30.6 LPG in foxes. Trichinella spiralis (sensu stricto) predominated over T. britovi in wild boars. Random amplified polymorphic DNA (RAPD) and alloenzyme typing showed that 74% of infected wild boars had only T. spiralis, 21% had only T. britovi, and 5% showed mixed infections. In contrast, 33% of infected foxes were infected only with T. spiralis, while 67% had T. britovi, suggesting a clear predominance of the latter in foxes. We suspect the existence of a paranthropic or sylvatic cycle in large areas of this region; given the ease of transfer between sylvatic and domestic or semi-domestic animals, this implies a high epidemiological risk.     

Levamisole can reduce bait monopolization in wild red foxes Vulpes vulpes

1. Baits are used worldwide to deliver vaccines, contraceptives and poison to wild animal species. In carnivores, multiple bait uptake and bait monopolization by dominant individuals may reduce baiting effectiveness. This study investigated whether a conditioned‐taste‐aversion agent, levamisole, can be used to decrease bait consumption by individual wild foxes Vulpes vulpes. 2. The results indicated that after consuming levamisole‐treated baits, foxes avoided eating treated baits but consumed untreated baits. We concluded that the reduction in bait consumption was achieved through learned aversion to levamisole rather than via conditioned‐taste‐aversion to baits. Adding levamisole to baits could potentially be used to reduce bait monopolization by individual wild foxes.     

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.     

Antibodies to Borrelia sp. in wild foxes and coyotes from Wisconsin and Minnesota

Serum samples from 93 red foxes (Vulpes vulpes) and nine gray foxes (Urocyon cinereoargenteus) trapped in Wisconsin and 23 coyotes (Canis latrans) trapped in Wisconsin and Minnesota were tested for antibodies to Borrelia sp. with an indirect fluorescent antibody test which used Borrelia burgdorferi as the whole-cell antigen. Seven red foxes (8%) and two coyotes (9%) had antibody titers greater than or equal to 1:64. All the positive samples were from areas known to be endemic for human Lyme disease. Implications for the epizootiology of Lyme borreliosis in wild canids are not well understood, but even if these species are not actual reservoirs of B. burgdorferi they could serve to increase the range of the vector and establish new endemic foci of the spirochete.     

Xylazine hydrochloride-ketamine hydrochloride immobilization of free-living red foxes (Vulpes vulpes) in Spain.

A combination of xylazine hydrochloride-ketamine hydrochloride was used to immobilize 83 wild red foxes (Vulpes vulpes) (15 pups and 68 adults) at Do?ana National Park (Spain). Mean ketamine hydrochloride doses were 17.1 mg/kg (SE = 1.53) and 12.3 mg/kg (SE = 0.4) for pups and adults, respectively, and mean xylazine hydrochloride doses for the same groups were 6.2 mg/kg (SE = 0.63) and 4.7 mg/kg (SE = 0.14), respectively. Mean induction times and first reaction times were 1.6 minutes and 22.5 minutes for pups and 3.8 minutes and 39.4 minutes for adults, respectively. Recommended doses for wild adult foxes of unknown weight are 75 mg of ketamine hydrochloride and 20 mg of xylazine hydrochloride.     

Diseases and parasites of red foxes, gray foxes, and coyotes from commercial sources selling to fox-chasing enclosures.

Fifty-six red foxes (Vulpes vulpes), 18 gray foxes (Urocyon cinereoargenteus), and 13 coyotes (Canis latrans) obtained by the South Carolina Wildlife and Marine Resources Department during an investigation of suspected illegal wildlife translocation were examined for diseases and parasites. Red foxes and coyotes were confiscated from an animal dealer based in Ohio (USA), and gray foxes were purchased from an animal dealer in Indiana (USA). Emphasis was placed on detection of pathogens representing potential health risks to native wildlife, domestic animals, or humans. All animals were negative for rabies; however, 15 gray foxes were incubating canine distemper at necropsy. Serologic tests disclosed antibodies to canine parvovirus, canine distemper virus, canine adenovirus, canine coronavirus, canine herpesvirus, and canine parainfluenza virus in one or more host species. Twenty-three species of parasites (two protozoans, three trematodes, four cestodes, eleven nematodes, and three arthropods) were found, including species with substantial pathogenic capabilities. Echinococcus multilocularis, a recognized human pathogen not enzootic in the southeastern United States, was found in red foxes. Based on this information, we conclude that the increasingly common practice of wild canid translocation for stocking fox-chasing enclosures poses potential health risks to indigenous wildlife, domestic animals, and humans and, therefore, is biologically hazardous.