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Background: In 2007, a previously unrecorded disease, fur animal epidemic necrotic pyoderma (FENP), was detected in farmed mink (Neovision vision), foxes (Vulpes lagopus) and Finnraccoons (Nyctereutes procyonoides) in Finland. Symptoms included severe pyoderma with increased mortality, causing both animal welfare problems and economic losses. In 2011, an epidemiologic questionnaire was mailed to all members of the Finnish Fur Breeders' Association to assess the occurrence of FENP from 2009 through the first 6 months of 2011. The aim was to describe the geographical distribution and detailed clinical signs of FENP, as well as sources of infection and potential risk factors for the disease. Results: A total of 239 farmers (25%) returned the questionnaire. Clinical signs of FENP were observed in 40% (95% CI 34-46%) of the study farms. In addition, the survey clarified the specific clinical signs for different animal species. The presence of disease was associated with the importation of mink, especially from Denmark (OR 9.3, 95% CI 2.6-33.0). The transmission route between Finnish farms was associated with fur animal purchases. Some risk factors such as the farm type were also indicated. As such, FENP was detected more commonly on farms with more than one species of fur animal in comparison to farms with, for example, only foxes (OR 4.6, 95% CI 2.4-8.6), and the incidence was higher on farms with over 750 breeder mink compared to smaller farms (OR 3.8, 95% CI 1.6-9.0). Contact between fur animals and birds and other wildlife increased the risk of FENP on farms. Responses also indicated that blocking the entry of wildlife to the animal premises protected against FENP. Conclusions: FENP was most likely introduced to Finland by imported mink and spread further within the country via domestically purchased fur animals. Some potential risk factors, such as the type and size of the farm and contact with wildlife, contributed to the spread of FENP. Escape-proof shelter buildings block the entry of wildlife, thus protecting fur animals against FENP. [ABSTRACT FROM AUTHOR]

The muscles of herbivores commonly harbor sarcocysts of parasites belonging to species in the genus Sarcocystis, but such muscle parasites are rare in carnivores. Here, we report Sarcocystis arctica-like sarcocysts in muscles of Arctic foxes ( Vulpes lagopus) from Alaska, USA, for the first time. The tongues of 56 foxes were examined for Sarcocystis infection using several methods. Sarcocystis bradyzoites were detected in pepsin digests of 13 (23.2%), and sarcocysts were found in histological sections stained with hematoxylin and eosin (HE) of 9 (16.0%). By light microscopy, sarcocysts were up to 4 mm long and up to 245 μm wide. In HE-stained sections, the sarcocyst wall appeared smooth and up to 1.5 μm thick without visible protrusions. By transmission electron microscopy, the sarcocyst wall had a wavy parasitophorous vacuolar membrane (pvm) folded as pleomorphic villar protrusions (vp), sometimes with anastomoses of villar tips. The vp and the ground substance (gs) layer were smooth and without microtubules. The gs was up to 2.0 μm thick. The total width of the wall including vp and the gs was up to 4.0 μm. The vp were up to 3.0 μm long and most closely resembled 'type 9c.' All sarcocysts were mature and contained numerous 8.1 × 2.1 μm sized bradyzoites. Molecular characterization (at 18S rDNA , 28S rDNA, ITS-1, and cox1) showed the highest affinity for S. arctica of the Arctic fox ( V. lagopus) from Norway. In the present investigation, we provide evidence that sarcocysts are common in tongues of Alaskan Arctic foxes suggesting that these carnivores are serving as intermediate hosts, and we also provide ultrastructure of S. arctica from the Arctic fox for the first time. [ABSTRACT FROM AUTHOR]

Reproductive experience affects juvenile survival in a wide range of species with possible links to differences in foraging capacity and predation. Using supplementary feeding, we aimed to limit direct effect of prey abundance to investigate indirect effects of small-rodent availability and maternal experience on juvenile summer survival rates in an endangered population of arctic fox ( Vulpes lagopus (L., 1758)). We used data spanning 7 years, included a complete small-rodent cycle, comprising 49 litters and 394 cubs. The effect of small-rodent abundance on juvenile survival depended on maternal breeding experience. Cubs born by first-time-breeding females had lower survival rate when small-rodent abundance was low compared with juveniles born to experienced mothers who remained unaffected. It was unlikely due to starvation, as physical condition was unrelated to survival. Instead, we favour the explanation that intraguild predation was an important cause of mortality. There was a negative relationship between survival and amount of time cubs were left unattended, suggesting that parental behaviour affected predation. We propose that a prey switch related to small-rodent abundance caused fluctuations in intraguild predation pressure and that inexperienced females were less able to cope with predation when small rodents were scarce. [ABSTRACT FROM AUTHOR]

Three digestibility experiments on Arctic foxes were carried out. Control groups were fed standard diets (C1 and C2) composed of fresh or frozen animal by-products and steamed ground grain. Dry experimental diets (E1 and E2) contained animal meals, extracted meals and fat, were mixed with water prior to administration. In a preliminary experiment, the digestibility of dry diet E1 moistened with water for 15min and 24h was compared to determine the optimum moistening time during the experimental period proper. The preliminary experiment showed that moistening time had no significant effect on digestibility. In the main experiment, two independent digestibility trials were performed to compare the digestibility of diets fed to foxes during growth (C1 vs. E1) and fur development (C2 vs. E2). Better nutrient digestibility was noted for control diets, compared to experimental. The greatest differences were reported for total protein digestibility. Protein contained in meals undergoes denaturation during heat treatment, which reduces digestibility. It was found that the retention of nitrogen in relation to nitrogen digestion was higher in foxes fed experimental diets (E1 and E2).

• An ABM was used to identify drivers of contact risk among Arctic foxes. • Broad-scale fox movement strategies were simulated using hidden Markov models. • Arctic fox migration and dispersal are drivers of contact risk. • Time spent in each behavior state of migration and dispersal affected contact rates. • Implications for Arctic rabies management were discussed. Arctic rabies is an ongoing threat to human populations and domestic animals inpolar regions, where Arctic foxes (Vulpes lagopus) are the main reservoir hosts. Human-driven changes in resource availability are shifting the distribution of Arctic foxes and these changes may affect the risk of rabies transmission and spread. Our understanding of the effects of broad-scale movement strategies in Arctic foxes and spatial distribution of resources on contact patterns among Arctic foxes, and their consequences on the dynamics of rabies epidemiology remains limited, in part, due to the difficulty of obtaining contact data from such remote and expansive regions. In this perspective, we built a spatially explicit agent-based model coupled with hidden Markov models to explore how Arctic fox movement behavior, combined with Arctic fox population density, resource availability and rabies transmission dynamics, affects the risk of infectious contact between Arctic foxes across heterogeneous landscapes. The model was parameterized using a combination of unique field data collected in the Canadian High Arctic and published studies from other Arctic regions. A sensitivity analysis was performed to assess the effects of multiple model input parameters on contact rates among Arctic foxes. Our results showed that cumulative contact rates per fox were driven by predictors related to rabies transmission dynamics and fox carrying capacity, while unique contact rates per fox and unique infectious contact rates per rabid fox were best predicted by parameters associated with rabies transmission dynamics, fox movement behavior, and fox carrying capacity. Ultimately, our study provides new insights into the ecological drivers of rabies transmission and may inspire further research on modelling cost-effective rabies prevention strategies in the Arctic. [ABSTRACT FROM AUTHOR]

The life cycle of Mesocestoides tapeworms (Cestoda: Cyclophyllidea: Mesocestoididae) requires three hosts. The first intermediate host is unknown but believed to be an arthropod. The second intermediate host is a vertebrate. The primary definitive host is a carnivore mammal, or a bird of prey, that eats the tetrathyridium-infected second intermediate host. One representative of the genus, Mesocestoides canislagopodis, has been reported from Iceland. It is common in the arctic fox ( Vulpes lagopus) and has also been detected in domestic dogs ( Canis familiaris) and cats ( Felis domestica). Recently, scolices of a non-maturing Mesocestoides sp. have also been detected in gyrfalcon ( Falco rusticolus) intestines, and tetrathyridia in the body cavity of rock ptarmigan ( Lagopus muta). We examined the taxonomic relationship of Mesocestoides from arctic fox, gyrfalcon, and rock ptarmigan using molecular methods, both at the generic level (D1 domain LSU ribosomal DNA) and at the specific level (cytochrome c oxidase subunit I (COI) and 12S mitochondrial DNA). All stages belonged to Mesocestoides canislagopodis. Phylogenetic analysis of the combined 12S-COI at the specific level confirmed that M. canislagopodis forms a distinct clade, well separated from three other recognized representatives of the genus, M. litteratus, M. lineatus, and M. corti/ vogae. This is the first molecular description of this species. The rock ptarmigan is a new second intermediate host record, and the gyrfalcon a new primary definitive host record. However, the adult stage seemed not to be able to mature in the gyrfalcon, and successful development is probably restricted to mammalian hosts. [ABSTRACT FROM AUTHOR]

Identifying correctly trophic interactions is important for understanding population dynamics and ecosystem functioning. However, some predator-prey relationships may still remain undetected, due to the difficulty of observing rare predation events. We report the first observation of predation of arctic fox ( Vulpes lagopus) pups by common ravens ( Corvus corax). The predation event was witnessed on Bylot Island, Nunavut, Canada, through an automatic camera placed on a den. On June 8, 2013, the day following pup emergence from the den, the complete litter of four was killed and taken away by a pair of ravens despite the intermittent presence of the mother. This event lasted 2.5 h, occurred during a low lemming year, and resulted in the fox pair failing their reproduction. Only two other fox litters were present that summer in our 600 km study area, so this litter predated by ravens accounted for 25 % (4/16) of the pups produced. Our report shows how continuous monitoring of dens using automatic cameras can allow documentation of rare events. In addition to food competition and cache raiding, pup predation contributes to the antagonistic interactions between arctic foxes and ravens in the High Arctic, which may intensify during low lemming years. This observation allows a better understanding of species interactions within the Arctic predator guild. [ABSTRACT FROM AUTHOR]

We analysed the willingness of blue foxes ( Vulpes lagopus ) to work for and utilise five resources: a platform, wooden block, sand floor, nest box and empty space. Ten juvenile blue fox males were housed singly in apparatus consisting of three cages connected with one-way doors through the walls in between the cages and subjected to work for each of the five resources, one at a time. The resource was placed in one of the outermost cages of the apparatus. Force needed to open the door leading to the resource cage was increased daily by 0.25 or 0.5 kg. The number of daily entries, visit durations and interaction with the resource were recorded on workloads of 0, 0.5, 1.5, 2.5, 3.5, 5, 6.5, and 8 kg of extra weight. The latency to start interacting with the resource after entering the resource cage was measured on a workload of 3.5 kg. The mean number of daily entries in the resource and the other outermost, i.e. control cage varied from 7 to 28 and from 17 to 44, respectively. The increasing workload decreased the number of entries in the resource cage, increased those in the control cage (Linear Mixed Model: F 1,638 = 79.5, P < 0.001) and lengthened the visit durations in both cages ( F 1,642 = 7.2, P < 0.01). The foxes made most ( F 4,643 = 9.0, P < 0.001) and shortest ( F 4,641 = 2.8, P < 0.05) visits to the outermost cages when the available resource was either a platform or empty space. The visit durations were longest when the available resource was a nest box. The foxes interacted regularly with the wooden block, but five foxes were not observed interacting with the platform. The nest box was utilised approximately 50% of the time spent in the resource cage, while the platform was utilised only 1–6% and wooden block 2–17% of the time. The mean latency to start interacting with the resource after entering the resource cage was shortest for the sand floor (8 s) and longest for the platform (113 s, F 3,335 = 26.3, P < 0.001). The results show that the foxes re-scheduled their activities on increasing workloads in the apparatus. Based on the number of entries and visit durations, blue foxes valued the wooden block, nest box and sand floor more than the platform or an empty cage. After entering the resource cage, the foxes started interacting fastest with the sand floor, showing high motivation to interact. After entering the resource cage, the foxes make use of the roof of the nest box more urgently than the interior of the nest box. Long bouts in the cage with nest box indicate resting behaviour. [ABSTRACT FROM AUTHOR]

For pathogens that infect multiple species, the distinction between reservoir hosts and spillover hosts is often difficult. In Alaska, three variants of the arctic rabies virus exist with distinct spatial distributions. We tested the hypothesis that rabies virus variant distribution corresponds to the population structure of the primary rabies hosts in Alaska, arctic foxes ( Vulpes lagopus) and red foxes ( Vulpes vulpes) to possibly distinguish reservoir and spillover hosts. We used mitochondrial DNA (mt DNA) sequence and nine microsatellites to assess population structure in those two species. mt DNA structure did not correspond to rabies virus variant structure in either species. Microsatellite analyses gave varying results. Bayesian clustering found two groups of arctic foxes in the coastal tundra region, but for red foxes it identified tundra and boreal types. Spatial Bayesian clustering and spatial principal components analysis identified 3 and 4 groups of arctic foxes, respectively, closely matching the distribution of rabies virus variants in the state. Red foxes, conversely, showed eight clusters comprising two regions (boreal and tundra) with much admixture. These results run contrary to previous beliefs that arctic fox show no fine-scale spatial population structure. While we cannot rule out that the red fox is part of the maintenance host community for rabies in Alaska, the distribution of virus variants appears to be driven primarily by the arctic fox. Therefore, we show that host population genetics can be utilized to distinguish between maintenance and spillover hosts when used in conjunction with other approaches. [ABSTRACT FROM AUTHOR]

Background: The genus Vulpes (true foxes) comprises numerous species that inhabit a wide range of habitats and climatic conditions, including one species, the Arctic fox (Vulpes lagopus) which is adapted to the arctic region. A close relative to the Arctic fox, the red fox (Vulpes vulpes), occurs in subarctic to subtropical habitats. To study the genetic basis of their adaptations to different environments, transcriptome sequences from two Arctic foxes and one red fox individual were generated and analyzed for signatures of positive selection. In addition, the data allowed for a phylogenetic analysis and divergence time estimate between the two fox species. Results: The de novo assembly of reads resulted in more than 160,000 contigs/transcripts per individual. Approximately 17,000 homologous genes were identified using human and the non-redundant databases. Positive selection analyses revealed several genes involved in various metabolic and molecular processes such as energy metabolism, cardiac gene regulation, apoptosis and blood coagulation to be under positive selection in foxes. Branch site tests identified four genes to be under positive selection in the Arctic fox transcriptome, two of which are fat metabolism genes. In the red fox transcriptome eight genes are under positive selection, including molecular process genes, notably genes involved in ATP metabolism. Analysis of the three transcriptomes and five Sanger re-sequenced genes in additional individuals identified a lower genetic variability within Arctic foxes compared to red foxes, which is consistent with distribution range differences and demographic responses to past climatic fluctuations. A phylogenomic analysis estimated that the Arctic and red fox lineages diverged about three million years ago. Conclusions: Transcriptome data are an economic way to generate genomic resources for evolutionary studies. Despite not representing an entire genome, this transcriptome analysis identified numerous genes that are relevant to arctic adaptation in foxes. Similar to polar bears, fat metabolism seems to play a central role in adaptation of Arctic foxes to the cold climate, as has been identified in the polar bear, another arctic specialist. [ABSTRACT FROM AUTHOR]

The temporal occurrence, spatial distribution, spread, and prevalence of rabies in Arctic foxes, Vulpes lagopus, in Greenland were studied using historical observations from 1969 to 2011 and survey data collected in the winters 1992 and 1993. Regionally, the prevalence of rabies ranged between 0 and 7.1 %. Wavelet analysis was used to identify periodicities in the abundance of rabies cases based on the historical observations. No general length of the cyclic interval of rabies occurrences in Greenland could be demonstrated. The frequency of outbreaks was found to be variable but can be grouped as short (less than 5 years), medium (5-10 years), and long (more than 10 years). Moreover, rabies outbreaks in neighboring regions were found to be more closely correlated compared to regions further apart. In West Greenland, the temporal outbreaks of rabies were found to occur along a north-south trajectory. [ABSTRACT FROM AUTHOR]

After infection with Trichinella spp. was first demonstrated in the arctic fox population in Svalbard 30 years ago, there have been changes in the Svalbard ecosystem related to abundance of polar bear and walrus, both reservoir species for Trichinella. In order to update the assessment of the infection rate and search for differences between sex, age, trapping season and location of trapping sites, we examined arctic foxes from Svalbard in 1996-2004 ( n = 429) for antibodies against Trichinella spp. For support and muscle larvae (ML) identification, the diaphragm of a subsample of 330 of the foxes, 40 foxes from 2007 to 2008, and a polar bear ( Ursus maritimus) tongue sample, were examined for ML by an HCl-pepsin digestion method. The antibody assay (enzyme-linked immunosorbent assay, ELISA) demonstrated a seroprevalence of 11.7 %. The prevalence increased with age, was similar in females and males, and body condition was similar in seropositives and seronegatives. There were differences in prevalence between trapping seasons and sites. A previously reported spatial (north-south) difference appeared to be eliminated. The seroprevalence was significantly higher in males (50.0 %) than females (20.0 %) of age 4 years and older. An ML prevalence of 6.7 % was demonstrated for the foxes. This was probably an underestimate due to small sample weights. ML were found also in the polar bear. Multiplex PCR identified eleven ML isolates, ten from the arctic foxes and the polar bear isolate, as Trichinella nativa. [ABSTRACT FROM AUTHOR]

The red fox ( Vulpes vulpes) expanded its distribution over large parts of the Canadian Arctic during the twentieth century and is now considered a threat to the arctic fox ( Vulpes lagopus). Some authors have proposed that the European red fox, introduced in Eastern North America during the eighteenth century, may have spread and caused the species' expansion in the Arctic. Assessing the biological origin of red foxes in the Nearctic is critical to determine whether their presence constitutes a case of an invading exotic species. We analyzed genetic material obtained from four red foxes at Herschel Island (Yukon) and Bylot Island (Nunavut), at the northern expanding front of the species. Samples from Bylot provide the northernmost genetic information on red fox obtained worldwide. We identified mitochondrial DNA haplotypes in red foxes from both Arctic locations that were phylogenetically divergent from those in Eurasia, but shared with neighboring indigenous North American populations. Thus, our results indicate that the twentieth century expansion of red foxes in the Canadian Arctic involved nearby populations potentially benefiting from habitat changes, rather than an exotic species invading new habitats. [ABSTRACT FROM AUTHOR]

Understanding how climate change and increasing human impacts may exert pressure on ecosystems and threaten biodiversity requires efficient monitoring programs. Indicator species have been proposed as useful tools, and predators and their diet may be particularly suitable. The vast and remote arctic tundra represents a good case study as shifts in ecosystem states are presently occurring, and monitoring is a major challenge. Here we assess what stable isotopes reflecting the diet of the arctic fox, a widespread and highly flexible top predator, can contribute to effective monitoring of the vertebrate prey basis of Arctic tundra. We used data collected over 2-5 years from six sites in the Eurasian Arctic and Greenland. Stable isotope signatures of arctic fox winter fur reflected both spatial and temporal variability in the composition of the vertebrate prey basis. Clear contrasts were apparent in the importance of marine resources, as well as of small rodents and their multiannual density fluctuations. Some important resources could however not be separated because of confounding isotopic signatures. Moreover, except for preferred prey, the proportions of prey in the diet may not necessarily reflect the relative importance of species in the community of available prey. Knowing these limitations, we suggest that the arctic fox diet as inferred from stable isotopes could serve as one of several key targets in ecosystem-based monitoring programs. [ABSTRACT FROM AUTHOR]

Male-biased parasite loads are common in vertebrates, particularly in species with intense sexual selection, yet few studies have examined sex-biased parasite loads in monogamous species with low sexual selection and no differential investment in ornaments or other sexually selected traits. The circumpolar arctic fox ( Vulpes lagopus) is a socially monogamous predator with low sexual selection; both parents invest heavily in their young. To determine if parasite loads (abundance and intensity) in arctic foxes vary with sex, age, or diet, we identified and enumerated parasites in arctic fox carcasses collected in winter from local trappers at Churchill, Manitoba, Canada. We measured stable isotope ratios in muscle samples as a proxy for diet. Males had more cestodes, which are only transmitted through prey, but numbers of nematodes, which are acquired by direct transmission, did not differ between sexes. δ15N values were lower in males, suggesting greater reliance on small mammals. Age did not affect diet or the number of cestodes, but the species of cestodes differed by age; for example, Echinococcus multilocularis was present only in subadults (< 1 year old). Nematodes were more abundant in subadults, likely because pups spend more time at dens in high densities, increasing exposure. Intraspecific differences in arctic fox parasites are best explained by variation in diet and foraging patterns, rather than hormone-mediated reduction in immunity. These results suggest that in monogamous species, males may not suffer compromised immunity as seen in species with strong sexual selection. [ABSTRACT FROM AUTHOR]

Sarcocysts were detected in routinely processed histological sections of skeletal muscle, but not cardiac muscle, of two adult male otters ( Lutra lutra; Mustelidae) from northern Norway following their post-mortem examination in 1999 and 2000. The sarcocysts were slender, spindle-shaped, up to 970 μm long and 35-70 μm in greatest diameter. The sarcocyst wall was thin (∼0.5 μm) and smooth with no visible protrusions. Portions of unfixed diaphragm of both animals were collected at the autopsies and kept frozen for about 14 years pending further examination. When the study was resumed in 2013, the thawed muscle samples were examined for sarcocysts under a stereo microscope, but none could be found. Genomic DNA was therefore extracted from a total of 36 small pieces of the diaphragm from both otters, and samples found to contain Sarcocystidae DNA were used selectively for PCR amplification and sequencing of the nuclear 18S and 28S ribosomal (r) RNA genes and internal transcribed spacer 1 (ITS1) region, as well as the mitochondrial cytochrome b ( cytb) and cytochrome c oxidase subunit 1 ( cox1) genes. Sequence comparisons revealed that both otters were infected by the same Sarcocystis sp. and that there was no genetic variation (100 % identity) among sequenced isolates at the 18S and 28S rRNA genes (six identical isolates at both loci) or at cox1 (13 identical isolates). PCR products comprising the ITS1 region, on the other hand, had to be cloned before sequencing due to intraspecific sequence variation. A total of 33 clones were sequenced, and the identities between them were 97.9-99.9 %. These sequences were most similar (93.7-96.0 % identity) to a sequence of Sarcocystis kalvikus from the wolverine in Canada, but the phylogenetic analyses placed all of them as a monophyletic sister group to S. kalvikus. Hence, they were considered to represent a novel species, which was named Sarcocystis lutrae. Sequence comparisons and phylogenetic analyses based on sequences of the 18S and 28S rRNA genes and cox1, for which little or no sequence data were available for S. kalvikus, revealed that S. lutrae otherwise was most closely related to various Sarcocystis spp. using birds or carnivores as intermediate hosts. The cox1 sequences of S. lutrae from the otters were identical to two sequences from an arctic fox, which in a previous study had been assigned to Sarcocystis arctica due to a high identity (99.4 %) with the latter species at this gene and a complete identity with S. arctica at three other loci when using the same DNA samples as templates for PCR reactions. Additional PCR amplifications and sequencing of cox1 (ten sequences) and the ITS1 region (four sequences) using four DNA samples from this fox as templates again generated cox1 sequences exclusively of S. lutrae, but ITS1 sequences of S. arctica, and thus confirmed that this arctic fox had acted as intermediate host for both S. arctica and S. lutrae. Based on the phylogenetic placement of S. lutrae, the geographical location of infected animals (otters, arctic fox) and the distribution of carnivores/raptors which may have interacted with them, the white-tailed eagle ( Haliaeetus albicilla) seems to be a possible definitive host of S. lutrae. Some of the muscle samples from both otters were shown to harbour stages of Toxoplasma gondii through PCR amplification and sequencing of the entire ITS1 region (five isolates) and/or the partial cytb (eight isolates) and cox1 (one isolate). These sequences were identical to several previous sequences of T. gondii in GenBank. Thus, both otters had a dual infection with S. lutrae and T. gondii. [ABSTRACT FROM AUTHOR]

In Svalbard, Norway, the only intermediate host for Echinococcus multilocularis, the sibling vole, has restricted spatial distribution. A survey of feces from the main host, the arctic fox, showed that only the area occupied by the intermediate host is associated with increased risk for human infection.

This review addresses biological effects of anthropogenic organohalogenated compounds in the arctic fox ( Vulpes lagopus ). When considering the current levels, spatial and tissue distributions of selected organic pollutants in arctic fox subpopulations, especially the Svalbard based populations accumulate high levels. The dominating contaminant groups are the polychlorinated biphenyls (PCBs) and chlordanes (CHLs), which reach high levels in adipose tissues, adrenals and liver. Recent controlled exposure studies on domesticated arctic fox and Greenland sledge dogs, show adverse health effects associated with OC concentrations lower than those measured in free-ranging populations. This indicates that especially populations at Svalbard may be at risk of experiencing OC related effects. The arctic fox as such may be an overlooked species in the Arctic Monitoring and Assessment Programs and it would add further information about pollution in the Arctic to include this species in the monitoring program. [ABSTRACT FROM AUTHOR]

Red foxes ( Vulpes vulpes (L., 1758)) recently expanded into the oil fields at Prudhoe Bay, Alaska, USA, and we hypothesized that the availability of anthropogenic foods may contribute to their success and persistence there. This study assessed the importance of anthropogenic foods to the diets of red foxes and arctic foxes ( Vulpes lagopus (L., 1758)), and competition for food resources between the two species in Prudhoe Bay. We used stable isotope analysis of fox tissues to infer diet during summer and winter for both red and arctic foxes, and lifetime diet for red fox. While the contribution of anthropogenic foods in late summer for both species' diets was low (~10% to 15%), the contribution in late winter was higher and varied between species (red foxes = 49%; arctic foxes = 39%). Estimates of lifetime diet in red foxes suggest consistent use of anthropogenic foods. We found moderate overlap of fox diets, although red foxes appeared to be more specialized on lemmings, whereas arctic foxes had a more diverse diet. Availability and consumption of anthropogenic foods by red foxes, particularly in winter, may partially explain their year-round presence in Prudhoe Bay. [ABSTRACT FROM AUTHOR]

In the twentieth century, red fox ( Vulpes vulpes) expanded into the Canadian Arctic, where it competes with arctic fox ( Vulpes lagopus) for food and shelter. Red fox dominates in physical interactions with the smaller arctic fox, but little is known about competition between them on the tundra. On Hershel Island, north Yukon, where these foxes are sympatric, we focused on natal den choice, a critical aspect of habitat selection. We tested the hypothesis that red fox displaces arctic fox from dens in prey-rich habitats. We applied an approach based on model comparisons to analyse a 10-year data set and identify factors important to den selection. Red fox selected dens in habitats that were more prey-rich in spring. When red foxes reproduced, arctic fox selected dens with good springtime access, notably many burrows unblocked by ice and snow. These provided the best refuge early in the reproductive season. In the absence of red foxes, arctic foxes selected dens offering good shelter (i.e. large isolated dens). Proximity to prey-rich habitats was consistently less important than the physical aspects of dens for arctic fox. Our study shows for the first time that red foxes in the tundra select dens associated primarily with prey-rich areas, while sympatric arctic foxes do not. These results fit a model of red fox competitively interfering with arctic fox, the first detailed study of such competition in a true arctic setting. [ABSTRACT FROM AUTHOR]

With increased polar anthropogenic activity, such as from the oil and gas industry, there are growing concerns about how Arctic species will be affected. Knowledge of species' sensory abilities, such as auditory sensitivities, can be used to mitigate the effects of such activities. Herein, behavioral audiograms of two captive adult Arctic foxes ( Vulpes lagopus) were measured using a yes/no paradigm and descending staircase method of signal presentation. Both foxes displayed a typical mammalian U-shaped audiometric curve, with a functional hearing range of 125 Hz-16 kHz (sensitivity ≤ 60 dB re: 20 μPa) and average peak sensitivity of 24 dB re: 20 μPa at 4 kHz. The foxes had a lower frequency range and sensitivity than would be expected when compared to previous audiograms of domestic dogs ( Canis familiaris) and other carnivores. These differences indicate Arctic foxes ( V. lagopus) may have a lower frequency range than previously expected, which was similar to the only other fox species tested to date, kit foxes (Vulpes macrotis). Alternatively, differences may be due to testing constraints, such as masking of test signals by ambient noise and/or an unintentionally trained conservative response bias, which most likely resulted in underestimated hearing curves. While results of this study should be interpreted with caution due to its limitations, findings indicate that foxes have a narrower frequency range than formerly presumed. Anthropogenic activities near fox habitats can mitigate their impacts by reducing noise at frequencies within the functional hearing range and peak sensitivities of this species. [ABSTRACT FROM AUTHOR]

Food availability can impact group formation in Carnivora. Specifically, it has been suggested that temporal variation in food availability may allow a breeding pair to tolerate additional adults in their territory at times when food abundance is high. We investigate group occurrence and intraspecific tolerance during breeding in a socially flexible canid, the arctic fox ( Vulpes lagopus). We compare Iceland and Sweden where resource conditions differ considerably. A breeding pair was the most common social unit in both populations, but as predicted, groups were more frequent where food abundance varied substantially between years (Sweden: 6 %) than where food availability was stable (Iceland: ≤2 %). Within Sweden, supplemental feeding increased group occurrence from 6 to 21 %, but there was no effect of natural variation in lemming ( Lemmus lemmus) availability since group formation was rare also at lemming highs. Thus, additional factors appeared to influence the trade-off between intraspecific territoriality and tolerance. We report two cases where related females showed enduring social relationships with good-neighbour strategies. Related females also engaged in alloparental behaviour in a 'fox town' with 31 foxes (4 adults, 3 litters). In contrast, when unrelated foxes bred close to each other, they moved or split their litters during summer, presumably because of territorial conflict. We suggest that fluctuating food availability is linked to group formation in this Arctic carnivore, but also when food availability increases, additional factors such as relatedness, alloparental benefits, competition and predator defence appear necessary to explain group formation. [ABSTRACT FROM AUTHOR]

Highlights: [•] Few studies report the endoparasites of North American arctic foxes. [•] Conventional, immunological, and molecular techniques detected parasites in arctic foxes at Karrak Lake, Nunavut. [•] Karrak Lake foxes are infected with common parasites of foxes with a terrestrial diet. [•] This study provides a comparison for future studies from the central Canadian Arctic. [Copyright &y& Elsevier]

Small isolated populations often show lower genetic variability. Demographic bottlenecks lead to loss of genetic variation too. Arctic foxes ( Vulpes lagopus) have been isolated since the Pleistocene on Mednyi and Bering Islands ( Commander Islands). In 1970-1980, the Mednyi population passed through a severe bottleneck due to a mange outbreak. Previous studies showed lack of genetic diversity in the contemporary Mednyi population that could be due to the long history of isolation and/or the recent bottleneck. To test both factors, we analyzed the mt DNA D-loop fragment and five microsatellites in pre-bottleneck Mednyi museum samples. Also, contemporary Mednyi, Bering and mainland Alaskan Arctic foxes were analyzed. Registered genetic variability in historical Mednyi was higher than in contemporary Mednyi Arctic foxes, but lower than in contemporary the Bering population. Our data confirms that the bottleneck reduced an already depleted polymorphism in Mednyi Arctic foxes. Lack of genetic variability could be a reason why the Mednyi population did not recover following the outbreak of mange. [ABSTRACT FROM AUTHOR]

Canids display pronounced intraspecific variation in social organization, ranging from single breeding females to large and complex groups. Despite several hypotheses in this matter, little is understood about the ecological factors underlying this flexibility. We have used the arctic fox ( Vulpes lagopus (L., 1758)) to investigate how contrasting ecosystem conditions concerning resources and predation influence group formation. We predicted that complex groups are more common in resource-rich ecosystems with predators, whereas simple groups occur in more marginal ecosystems without predators. Samples from 54 groups were collected from four populations of arctic foxes with contrasting prey resources and predation and these samples were genotyped in 10 microsatellite loci. We found considerable variation between ecosystems and a significant relationship between resources and formation of complex groups. We conclude that sufficient amounts of food is a prerequisite for forming complex groups, but that defense against predation further increases the benefits of living in larger groups. We present a conceptual model suggesting that a trade-off between the cost of resource depletion and the benefits obtained for guarding against predators explain the differences in social organization. The variable ecology of the arctic foxes makes it is a plausible model species for understanding the connection between ecology and social organization also in other species. [ABSTRACT FROM AUTHOR]

During the last century, the red fox ( Vulpes vulpes) has expanded its distribution into the Arctic, where it competes with the arctic fox ( Vulpes lagopus), an ecologically similar tundra predator. The red fox expansion correlates with climate warming, and the ultimate determinant of the outcome of the competition between the two species is hypothesized to be climate. We conducted aerial and ground fox den surveys in the northern Yukon (Herschel Island and the coastal mainland) to investigate the relative abundance of red and arctic foxes over the last four decades. This region has undergone the most intense warming observed in North America, and we hypothesized that this climate change led to increasing dominance of red fox over arctic fox. Results of recent surveys fall within the range of previous ones, indicating little change in the relative abundance of the two species. North Yukon fox dens are mostly occupied by arctic fox, with active red fox dens occurring sympatrically. While vegetation changes have been reported, there is no indication that secondary productivity and food abundance for foxes have increased. Our study shows that in the western Arctic of North America, where climate warming was intense, the competitive balance between red and arctic foxes changed little in 40 years. Our results challenge the hypotheses linking climate to red fox expansion, and we discuss how climate warming's negative effects on predators may be overriding positive effects of milder temperatures and longer growing seasons. [ABSTRACT FROM AUTHOR]

Abstract: Examination of terminal Pleistocene-age fox remains from the Marmes archaeological site in southeastern Washington State (USA) reveals that a previous identification of one specimen as arctic fox (Vulpes lagopus) was incorrect. Of nearly four-dozen associated specimens, eleven, including the one originally identified as arctic fox, represent red fox (Vulpes vulpes). Cut-marked fox bones and associated stone artifacts and eyed bone needles suggest several foxes were butchered and perhaps hides sewn together. The modern environmental setting of the Marmes site is too warm for modern red fox; the prehistoric red fox remains suggest (summer) climate was cooler when those remains were deposited. [Copyright &y& Elsevier]

1. Flows of nutrients and energy across ecosystem boundaries have the potential to subsidize consumer populations and modify the dynamics of food webs, but how spatio-temporal variations in autochthonous and allochthonous resources affect consumers' subsidization remains largely unexplored. 2. We studied spatio-temporal patterns in the allochthonous subsidization of a predator living in a relatively simple ecosystem. We worked on Bylot Island (Nunavut, Canada), where arctic foxes ( Vulpes lagopus L.) feed preferentially on lemmings ( Lemmus trimucronatus and Dicrostonyx groenlandicus Traill), and alternatively on colonial greater snow geese ( Anser caerulescens atlanticus L.). Geese migrate annually from their wintering grounds (where they feed on farmlands and marshes) to the Canadian Arctic, thus generating a strong flow of nutrients and energy across ecosystem boundaries. 3. We examined the influence of spatial variations in availability of geese on the diet of fox cubs (2003-2005) and on fox reproductive output (1996-2005) during different phases of the lemming cycle. 4. Using stable isotope analysis and a simple statistical routine developed to analyse the outputs of a multisource mixing model (SIAR), we showed that the contribution of geese to the diet of arctic fox cubs decreased with distance from the goose colony. 5. The probability that a den was used for reproduction by foxes decreased with distance from the subsidized goose colony and increased with lemming abundance. When lemmings were highly abundant, the effect of distance from the colony disappeared. The goose colony thus generated a spatial patterning of reproduction probability of foxes, while the lemming cycle generated a strong temporal variation of reproduction probability of foxes. 6. This study shows how the input of energy owing to the large-scale migration of prey affects the functional and reproductive responses of an opportunistic consumer, and how this input is spatially and temporally modulated through the foraging behaviour of the consumer. Thus, perspectives of both landscape and foraging ecology are needed to fully resolve the effects of subsidies on animal demographic processes and population dynamics. [ABSTRACT FROM AUTHOR]

1. Input of external subsidies in the Arctic may have substantial effects on predator populations that otherwise would have been limited by low local primary productivity. 2. We explore life-history traits, age-specific fecundity, litter sizes and survival, and the population dynamics of an Arctic fox ( Vulpes lagopus) population to explore the influence of the spatial distribution and temporal availability of its main prey; including both resident and migrating (external) prey resources. 3. This study reveals that highly predictable cross-boundary subsidies from the marine food web, acting through seasonal access to seabirds, sustain larger local Arctic fox populations. Arctic fox dens located close to the coast in Svalbard were found to have higher occupancy rates, as expected from both high availability and high temporal and spatial predictability of prey resources (temporally stable external subsidies). Whereas the occupancy rate of inland dens varied between years in relation to the abundance of reindeer carcasses (temporally varying resident prey). 4. With regard to demography, juvenile Arctic foxes in Svalbard have lower survival rates and a high age of first reproduction compared with other populations. We suggest this may be caused by a lack of unoccupied dens and a saturated population. [ABSTRACT FROM AUTHOR]

Many species of colonial ground-nesting birds are known to be sensitive to predation by terrestrial predators. The response of prey under the pressure of predation can either be direct (depletion of prey) or indirect due to prey avoiding the predator. We studied the recolonization of arctic foxes into a large and growing breeding colony of lesser black-backed gulls. The gull colony reached the size of 20,000 pairs during the period of no foxes. The number of breeding gulls continued to increase after the colonization of foxes and reached a maximum of 40,000 pairs about 15 years later. During the same time period, the spatial coverage of the gull colony shrunk from 31.4 down to 18.6 km², and the change in distribution was closely linked with position of fox dens, which ranged in number from one to three annually. In 2005, the number of breeding gulls decreased slightly with an ongoing shrinkage in spatial coverage. Food analyses from fox scats and stomachs showed that birds of the order Charadriiformes, particularly gulls, were the key prey item. Survival rates of gull nests were higher in the middle of the colony than at the colony edge close to a fox den. The colony area lost could be explained solely by the number of eggs removed by foxes but is unlikely, e.g., due to reclutching. We suggest that intraspecific predation contributes additionally to the effects of direct fox predation although to an unknown degree. [ABSTRACT FROM AUTHOR]

Arctic foxes are highly mobile arctic predators with a very weak population genetic structure over large parts of their range. Less is, however, known about the more local genetic structure within regions. Here, we analyze genotypes at 12 microsatellite loci for 561 arctic foxes trapped in the high-arctic archipelago Svalbard and investigate the genetic structure in three different age classes. Significant linkage disequilibrium, deficit of heterozygotes, genetic differentiation, and a decrease in relatedness with distance among animals trapped in their first winter suggested that some litter mates remain in proximity of each other during the first winter. This pattern was stronger for females than for males, indicating male-biased juvenile dispersal, and weaker for older animals. There was no genetic differentiation among adult foxes harvested in different hunting areas. The foxes from the protected area around Hornsund were however more differentiated than expected based on geographic distance alone, suggesting a possible disrupting effect of harvest on the spatial genetic structure in the rest of Svalbard. Our results also indicated a possible kin structure among adult females, suggesting natal philopatry, but further investigations will be needed to reach firm conclusions concerning kin structure in arctic foxes. [ABSTRACT FROM AUTHOR]

Extrapair paternity (EPP) is described in many socially monogamous species, but within-population variability in its frequency is poorly documented. Availability and distribution of food may influence polyandrous behaviors, either directly by affecting the need for paternal care or indirectly via their effect on population density. We quantified the frequency of EPP in a population of arctic foxes (Vulpes lagopus), a predominantly socially monogamous species with high paternal investment. We then tested whether spatial (presence of a goose colony) and temporal (cycles of lemmings) variations in food availability were linked to variations in mating systems within the population. From 2003 to 2008, we studied the mating systems of arctic foxes on Bylot Island (Nunavut, Canada) by combining molecular analyses with behavioral observations during cub rearing. Although the dominant social mating system was monogamy, at least 31% of cubs with known social father were born from extrapair matings (in 10 of 38 litters sampled). Likelihood of EPP was associated with food availability. It was greatest (86%) at the center of the goose colony and decreased sharply with increasing distance from it. EPP can thus be frequent in the socially monogamous arctic fox, and intraspecific variability in extrapair matings is strongly correlated with food availability during cub rearing. [ABSTRACT FROM PUBLISHER]

Here, we report from the first direct observation of a red fox ( Vulpes vulpes) intrusion on an arctic fox ( Vulpes lagopus) breeding den from the southern Arctic tundra of Yamal Peninsula, Russia in 2007. At the same time, as a current range retraction of the original inhabitant of the circumpolar tundra zone the arctic fox is going on, the red fox is expanding their range from the south into arctic habitats. Thus, within large parts of the northern tundra areas the two species are sympatric which gives opportunities for direct interactions including interference competition. However, direct first-hand observations of such interactions are rare, especially in the Russian Arctic. In the present study, we observed one red fox taking over an arctic fox breeding den which resulted in den abandonment by the arctic fox. On July 19, eight arctic fox pups were observed on the den before the red fox was observed on the same den July 22. The pups were never seen at the den or elsewhere after the red fox was observed on the den for as long as we stayed in the area (until August 10). Our observation supports the view that direct interference with red fox on breeding dens may contribute to the range retraction of arctic foxes from the southern limits of the Arctic tundra in Russia. [ABSTRACT FROM AUTHOR]

Seven Arctic fox puppies were found to have an extra claw (resembling a canine dewclaw) on their thoracic limb. These individuals came from 2 litters born of 2 different females. The "dewclaw" comprised a claw loosely connected with the limb by soft tissue, and it had the third phalanx (PIII) and a vestigial phalanx. Our results show that the presence of an extra claw on one or both hands in some Arctic fox puppies may, but does not have to, be a dominant trait. The differences between the 2 analyzed litters support the hypothesis that the mode of inheritance of the investigated trait in Arctic foxes could be more complex. [ABSTRACT FROM AUTHOR]

Abstract: Adiponectin is a novel adipocyte-derived hormone with low circulating concentrations and/or mRNA expression in obesity and non-alcoholic fatty liver disease (NAFLD). The adiponectin mRNA of several Carnivora species was sequenced to enable further gene expression studies in this clade with potential experimental species to examine the connections of hypoadiponectinemia to hepatic lipidosis. In addition, adiponectin mRNA expression was studied in the retroperitoneal fat of the American mink (Neovison vison), as hepatic lipidosis with close similarities to NAFLD can be rapidly induced to the species by fasting. The mRNA expression was determined after overnight–7d of food deprivation and 28d of re-feeding and correlated to the liver fat %. The homologies between the determined carnivoran mRNA sequences and that of the domestic dog were 92.2–99.1%. As the mRNA expression was not affected by short-term fasting and did not correlate with the liver fat %, there seems to be no clear connection between adiponectin and the development of lipidosis in the American mink. In the future, the obtained sequences can be utilized in further studies of adiponectin expression in comparative endocrinology. [ABSTRACT FROM AUTHOR]

The article discusses a study on whether Arctic foxes can be fed dry diets containing animal meals moistened with water including an analysis of the effect of moistening time on nutrient digestibility. The experiment included ten clinically healthy female Arctic blue foxes averaging four-month-old. The study indicates that standard traditional diets are characterized by better nutrient digestibility and concludes that farmed Arctic foxes should still be fed traditional prepared diets.

In July 2008 we outfitted reproductively active adult arctic foxes with satellite tracking collars on Bylot Island, Nunavut, Canada and recorded their movements over a complete annual cycle. We present the tracking data from two individuals, one female and one male, who traveled extensively from February to July 2009, covering minimum distances of 4,599 and 2,193 km, respectively. We recorded high and sustained travel rates on both land and sea ice that reached 90 km/day for the female and 88 km/day for the male. Our data confirm that arctic foxes can move extensively and demonstrate sustained travel rates that are 1.5 times those previously measured for the species. Our study is the first presenting detailed year-round satellite tracking of adult arctic foxes and has implications for our understanding of navigational abilities, foraging ecology, trophic interactions with lemming populations, and genetic population structure of arctic foxes. [ABSTRACT FROM AUTHOR]

One obvious threat to the endangered arctic fox Vulpes lagopus population in Fennoscandia is competition with the larger red fox Vulpes vulpes, which may have expanded its range towards the alpine tundra because of increased food availability in the low-alpine and subalpine region. The steady increase in the number of vacation cabins and roads, and thus also in human garbage and road-killed animals, may subsidise easily available food resources and improve red fox survival in these otherwise marginal areas. In Børgefjell National Park, Norway, 14 of 27 known arctic fox dens were used by arctic fox during 2001-2005. The dens that were used were situated at higher altitudes, farther from natural red fox habitats, than unused dens. In the best of our logistic regression models, there was also a statistical negative effect of the number of cabins within 7×7 km squares around the den sites. Hence, our results support the prediction that the arctic fox is less likely to use areas where human activity might be benefiting red foxes. A successful conservation strategy for the arctic fox will probably require a reduction of the driving forces behind the red fox expansion in the alpine areas. [ABSTRACT FROM AUTHOR]

The benefits and challenges of integrating traditional ecological knowledge and scientific knowledge have led to extensive discussions over the past decades, but much work is still needed to facilitate the articulation and co-application of these two types of knowledge. Through two case studies, we examined the integration of traditional ecological knowledge and scientific knowledge by emphasizing their complementarity across spatial and temporal scales. We expected that combining Inuit traditional ecological knowledge and scientific knowledge would expand the spatial and temporal scales of currently documented knowledge on the arctic fox (Vulpes lagopus) and the greater snow goose (Chen caerulescens atlantica), two important tundra species. Using participatory approaches in Mittimatalik (also known as Pond Inlet), Nunavut, Canada, we documented traditional ecological knowledge about these species and found that, in fact, it did expand the spatial and temporal scales of current scientific knowledge for local arctic fox ecology. However, the benefits were not as apparent for snow goose ecology, probably because of the similar spatial and temporal observational scales of the two types of knowledge for this species. Comparing sources of knowledge at similar scales allowed us to gain confidence in our conclusions and to identify areas of disagreement that should be studied further. Emphasizing complementarities across scales was more powerful for generating new insights and hypotheses. We conclude that determining the scales of the observations that form the basis for traditional ecological knowledge and scientific knowledge represents a critical step when evaluating the benefits of integrating these two types of knowledge. This is also critical when examining the congruence or contrast between the two types of knowledge for a given subject. [ABSTRACT FROM AUTHOR]

Abstract: We measured how much adult blue fox males value access to a nest box and sand floor enrichments while a platform and activity object are available simultaneously. Ten blue fox males were solitary housed in test apparatuses with permanent access to a platform and wooden block (activity object) during the breeding season. The foxes could gain access to either a nest box, a sand floor or to empty space by passing through a weighted one-way door on workloads increasing every 24h. The foxes’ behaviour was recorded on workloads of 0, 1.5, 3, and 5kg of extra weight. The foxes were highly active during the study. As the workload increased, the number of visits and the time spent in the cage with the resource decreased. This trend was most evident in the case of the sand floor. However, the workload did not affect the actual time spent interacting with the nest box or sand floor. The foxes utilised the sand floor and nest box more than the permanently available platform and wooden block. The present results suggest that during the breeding season, adult blue fox males are highly motivated to explore the accessible area and they value access to both a sand floor and nest box. [Copyright &y& Elsevier]