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Predator-prey dynamics in the Arctic are being altered with changing sea ice phenology. The increasing frequency of predation on colonial nesting seabirds and their eggs by the polar bear (Ursus maritimus) is a consequence of bears shifting to terrestrial food resources through a shortened seal-hunting season. We examined antipredator responses in a colony of nesting Common Eiders (Somateria mollissima) on East Bay Island, Nunavut, Canada, which is exposed to established nest predators, such as arctic fox (Vulpes lagopus), but also to recent increases in polar bear nest predation due to the bears’ lost on-ice hunting opportunities. Given eiders’ limited eco-evolutionary experience with bears, we aimed to experimentally contrast eider responses to the recent predation pressure by polar bears to those induced by their more traditional mammalian predator, the arctic fox. Our goal was to characterize whether this population of eiders was vulnerable to a changing predator regime. Using simulated approaches of visual stimuli of both predator types, we measured eider heart rate and flight initiation distance as physiological and behavioral metrics, respectively, to characterize the perceived risk of and subsequent response to imminent threat posed by these two predators that differ in historical encounter rates. Eider heart rates were more responsive to impending visual cues of arctic foxes compared to polar bears, but birds responded behaviorally to all simulated threats with similar flight initiation distances. Results suggest eiders may not perceive the full risk that bears pose as egg and adult predators, and are therefore expected to suffer negative fitness consequences from this ongoing and increasing interaction. Eiders may therefore require conservation intervention to aid in their management.

Prey handling processes are considered a dominant mechanism leading to short‐term positive indirect effects between prey that share a predator. However, a growing body of research indicates that predators are not necessarily limited by such processes in the wild. Density‐dependent changes in predator foraging behavior can also generate positive indirect effects but they are rarely included as explicit functions of prey densities in functional response models. With the aim of untangling proximate mechanisms of species interactions in natural communities and improving our ability to quantify interaction strength, we extended the multi‐prey version of the Holling disk equation by including density‐dependent changes in predator foraging behavior. Our model, based on species traits and behavior, was inspired by the vertebrate community of the arctic tundra, where the main predator (the arctic fox) is an active forager feeding primarily on cyclic small rodent (lemming) and eggs of various tundra‐nesting bird species. Short‐term positive indirect effects of lemmings on birds have been documented over the circumpolar Arctic but the underlying mechanisms remain poorly understood. We used a unique data set, containing high‐frequency GPS tracking, accelerometer, behavioral, and experimental data to parameterize the multi‐prey model, and a 15‐year time series of prey densities and bird nesting success to evaluate interaction strength between species. We found that (1) prey handling processes play a minor role in our system and (2) changes in arctic fox daily activity budget and distance traveled can partly explain the predation release on birds observed during lemming peaks. These adjustments in predator foraging behavior with respect to the main prey density thus appear as the dominant mechanism leading to positive indirect effects commonly reported among arctic tundra prey. Density‐dependent changes in functional response components have been little studied in natural vertebrate communities and deserve more attention to improve our ability to quantify the strength of species interactions. [ABSTRACT FROM AUTHOR]

A statistical analysis of the secondary (at birth) sex ratio in the farming population of the American mink (Neovison vison Schr.) of the standard dark brown breed was carried out. The study was done on the materials of the Pushkin breeding farm in Moscow oblast according to the pedigree books. A total of 1550 litters of 999 mink females were analyzed. The total sample size for 5 years was 10 372 kits. On the basis of the results of the analysis in the expected population, the birth rate of males is estimated to be 0.492 ± 0.0067 with a 95% confidence interval of 0.473 ≤ P(A) ≤ 0.511. Unlike other main species of farming fur-bearing animals, namely, arctic foxes, foxes, and sables, in the American mink, the secondary sex ratio is characterized by inconstancy and heterogeneity with a variable predominance of females or males in the offspring, depending on paratypic factors (mother's age and litter size). At the same time, as mothers age, the deviation of the sex ratio shifts toward the predominance of males in the offspring and, with an increase in the size of the litter, toward an increase in the number of females. [ABSTRACT FROM AUTHOR]

Anthropogenic debris, including plastic pollution, is a growing concern in the Arctic and negatively impacts both marine and coastal organisms. The aim of this study was to investigate the potential for using Arctic fox (Vulpes lagopus) faeces as a monitoring tool for plastic pollution in the Arctic environment. Arctic fox faeces were collected in different regions of Iceland and analysed for anthropogenic debris presence larger than 300 µm, and diet composition. In total, 235 faecal samples from 1999, 2017, 2018 and 2020 were analysed. The overall frequency of occurrence of plastic and other anthropogenic material was 5.11% and was found in samples across all regions and years. There were no statistical differences in anthropogenic debris ingested, depending on year or region. There were no obvious differences in diet composition between samples that contained anthropogenic debris and samples without. The suitability of Arctic fox faeces as a method to monitor plastic and anthropogenic debris levels in the Arctic environment remains debatable: Whilst the vast distribution range of the Arctic fox and the non-invasive collection methodology of faecal samples could be utilised as a good monitoring tool, the overall low uptake and unclear source of plastic and anthropogenic debris (marine or terrestrial) makes the interpretation of the data difficult. Nevertheless, debris ingestion by Arctic foxes remains a concern and warrants further studies. [ABSTRACT FROM AUTHOR]

Getah virus (GETV) is a zoonotic virus transmitted by mosquitoes, belonging to the Togaviridae family, Alphavirus genus. It was first isolated from mosquitoes in Malaysia in 1955, being widespread in island countries in the South Pacific region. Since the beginning of the 21st century, GETV expanded its range and geographical distribution from low-latitude tropical regions to 60° north latitude, being isolated from 17 different species of mosquitoes belonging to five genera of Culicidae (Culex, Anopheles, Armigeres, Aedes and Mansonia), as well as from midges in Eurasia. Molecular genetic evolution analysis revealed large molecular differences between the mosquitoes currently circulating Eurasia and those in the South Pacific in 1950s. The number of disease outbreaks caused by GETV in animals is increasing alongside the types of animals infected, from horses and pigs to cattle, blue foxes and red pandas. The disease burden is severely underestimated, and the economic cost to livestock production remains unknown. Herein, we review GETV temporal and spatial distribution, molecular genetic evolution, transmission and data on disease outbreaks. This work provides a reference for public health workers engaged in GETV research and zoonotic disease prevention and control. [ABSTRACT FROM AUTHOR]

Simple Summary: Nutrient requirements have previously been established for minks and foxes, but not specifically for blue foxes. Over the past thirty years, an increase in body size was observed in the farmed blue fox because of the development of modern breeding technology. Hence, it is necessary to study the interaction mechanisms and requirements of calcium (Ca) and vitamin D3 (VD3) according to the body weights and conditions of farmed blue foxes to guide modern farms. The objective of the present study was to study the influence of dietary Ca and VD3 supplemental levels on the nutrient digestibility, growth performance, and serum biochemical indices of growing blue foxes. The results indicated that the Ca and VD3 doses showed promising effects on growth performance and nutrient digestibility in growing blue foxes and could reduce fecal nitrogen (N) and phosphorus (P) via improvement in protein and P utilization. Based on the randomized design, a 3 × 3 factorial experiment was designed to examine the effects of dietary calcium (Ca), phosphorus (P), and vitamin D3 (VD3) supplemental levels with a fixed 1.5/1 ratio of Ca to P on the growth performance, nutrient digestibility, and serum biochemical indices blue foxes' growth. In total, 135 male blue foxes with the age of 60 days were randomly divided into 9 groups each with 15 blue foxes. The blue foxes belonging to the nine treatment groups were fed Ca supplementation (0%, 0.4%, or 0.8%) and VD3 supplementation (1000, 2000, or 4000 IU/kg DM). The base diet contained 0.8% Ca and 327 IU/kg VD3. The dosage of VD3 in blue foxes showed a significant impact on their growth performance (p < 0.05). The Ca dosage had a linear effect on the digestibility of the CP and carbohydrates (CHO) (p < 0.05). In conclusion, the results indicated that the Ca and VD3 doses showed promising effects on growth performance and nutrient digestibility in growing blue foxes and could reduce fecal N and P via improvement in protein and P utilization. [ABSTRACT FROM AUTHOR]

Rabies is an important zoonotic disease with high fatality rates in animals and humans. In the Arctic, the Arctic fox (Vulpes lagopus) is regarded as the principal reservoir, but there is considerable debate about how the disease persists at the low population densities that are typical for this species. We describe an outbreak of rabies among Arctic foxes and Svalbard reindeer (Rangifer tarandus platyrhynchus) during 2011–12 on the remote Arctic archipelago of Svalbard, an area with a very low and relatively stable Arctic fox density. The aim of the research was to increase knowledge of Arctic rabies in this ecosystem and in the presumed spillover host, the Svalbard reindeer. Phylogenetic analysis of rabies virus (RABV) RNA isolates from Arctic fox and reindeer was performed, and clinical observations and histologic and immunohistochemical findings in reindeer were described. An ongoing capture-mark-recapture project allowed collection of serum samples from clinically healthy reindeer from the affected population for detection of rabies virus–neutralizing antibodies. The outbreak was caused by at least two different variants belonging to the RABV Arctic-2 and Arctic-3 clades, which suggests that rabies was introduced to Svalbard on at least two different occasions. The RABV variants found in Arctic fox and reindeer were similar within locations, suggesting that Arctic foxes and reindeer acquired the infection from the same source(s). The histopathologic and immunohistochemical findings in 10 reindeer were consistent with descriptions in other species infected with RABV of non-Arctic lineages. Evidence of RABV was detected in both brain and salivary gland samples. None of 158 examined serum samples from clinically healthy reindeer had virus-neutralizing antibodies against RABV. [ABSTRACT FROM AUTHOR]

Simple Summary: Given the shortage of fish meal, other animal protein replacements are actively being researched. One such alternative is fly maggot protein—a highly nutritious insect protein containing chitin, lysozyme, and other biologically active substances. The purpose of this study was to examine how the replacement of fish meal with fly maggot protein affects growth, immune indexes, antioxidant levels, and fecal microflora in blue foxes (Alopex lagopus) during weaning. The results showed that fly maggot protein replacement had no adverse effects on the growth, immune indexes, and antioxidant levels of blue foxes at weaning. Further, it could modulate the fecal microflora. This indicates that fly maggot protein can serve as a novel animal protein alternative to fish meal for feeding blue foxes. Dietary protein is a key nutritional parameter and warrants special attention in animal husbandry. This study aimed to evaluate the effect of replacing fish meal (F) with fly maggot protein (M) on the growth performance, antioxidant levels, immune indexes, and fecal microflora in weaned blue foxes (Alopex lagopus). Twenty weaned blue foxes were randomly assigned to the control (F diet; 6% of F) or experimental (M diet; F substituted by M) group (10 blue foxes per group). The duration of the trial was 28 days. The results showed that there was no significant difference in average daily gain between group M and group F during the experiment (p = 0.473). Moreover, the diarrhea index was similar between group M and group F during the entire experimental period (p = 0.112). At the end of the experiment, the levels of IL-6 and IgG in group M at 28 d were significantly higher than that in group F (p = 0.004, p = 0.025, respectively), but not IL-1β, IL-2, SIgA, IgM, and TNF-α. The levels of SOD in group M at 28 d were significantly higher than those in group F (p = 0.001), and no difference of MDA and T-AOC was found between group F and M (p = 0.073, p = 0.196, respectively). In both groups, the diversity of fecal microbes first increased and then decreased with the progress of the experimental period. Initially, there were differences in the composition of microbial communities between the two groups. However, this difference was attenuated at later stages of the experimental period. In conclusion, fly maggot protein can replace fish meal as a source of animal protein in feed material for blue foxes during the weaning period. [ABSTRACT FROM AUTHOR]

Colonial nesting is associated with numerous costs and benefits that may either increase or decrease fitness of individuals in colonies. Fitness can vary as a function of the location within colonies and individuals may attempt to improve their fitness by changing their nesting location between years. We used a 24 year data set on nest locations within the Tutakoke River Black Brant (Branta bernicla nigricans) colony on the Yukon-Kuskokwim Delta in western Alaska and multi-state capture-mark-recapture models to study the movement of individuals between 2 spatial strata in the colony separated by the Tutakoke River. We found that individuals nesting in a stratum that experienced higher levels of predation by arctic foxes (Vulpes lagopus) were 3 times more likely to move to the other stratum than vice versa, despite slightly higher risk of tidal flooding in the second stratum. These results suggest that Black Brant changed nest locations in an attempt to maximize reproductive fitness and they are consistent with a long-term shift in nest density over the course of the study. La anidación en colonias está asociada con numerosos costos y beneficios que pueden aumentar o reducir la sobrevivencia de individuos en colonias. La sobrevivencia puede variar en función de la localización del nido al interior de la colonia y los individuos pueden intentar mejoras en su sobrevivencia mediante el cambio de sitio de anidación en diferentes años. Usamos un juego de datos de localización de nidos de 24 años en la colonia de gansos Branta bernicla nigricans del río Tutakoke en el delta del Yukon-Kuskokwin en el occidente de Alaska y modelos multiestado de capura-marcado-recaptura para estudiar el movimiento de individuos entre 2 estratos espaciales en la colonia separados por el río Tutakoke. Encontramos que los individuos anidando en un estrato que experimentó mayores niveles de depredación por zorros del Ártico (Vulpes lagopus) tenían una probabilidad 3 veces mayor de moverse al otro estrato que viceversa, aún pese a un ligeramente mayor riesgo de inundación por mareas en el segundo estrato. Estos resultados sugieren que estos gansos cambiaron la ubicación de sus nidos para intentar maximizar su sobrevivencia reproductiva y son consistentes con un cambio a largo plazo en la densidad de nidos a largo plazo a lo largo del periodo de este estudio. Palabras clave: ártico, colonialidad, dispersión, ganso, información privada, información pública, multi-estado. [ABSTRACT FROM AUTHOR]

This article discusses the penetration of fox and human skulls into granular matter, specifically focusing on the study of the artic fox's ability to dive into snow to catch prey. The authors compare their own study of a human skull sinking into granular matter to the study of the fox skull, noting that nonsymmetric objects tend to rotate and depart from vertical plunge. They also mention the need for further experiments to fully understand the biomechanics of mousing in real life. Overall, the article highlights the complexity of studying the penetration of objects into granular beds and the challenges of investigating realistic objects. [Extracted from the article]

"We are shaped, to a greater extent than almost any other species, by contact with others. [...] Yet what counts now is to win. [...] And for this, we have ripped the natural world apart" (Monbiot). This quote stems from a Guardian article that is also printed as an epigraph in Tanya Ronder's 2015 play Fuck the Polar Bears, and it reveals the connection between the Capitalocene, as described by Jason W. Moore, and contemporary eco-drama: both thematise the "Age of Loneliness" (Monbiot) in which everyone fights against each other. In contemporary drama, this behaviour is frequently reflected in the depiction of isolation and alienation from nature that is expressed in the form of disgust, for instance, by making objects that are associated with nature literally or metaphorically disgusting.To various degrees, the depiction of the Capitalocene in combination with disgust and abjection can be found in Fuck the Polar Bears as well as in Dawn King's 2011 play Foxfinder. In both plays, disgust is depicted as degrading the relationship between humans and nonhuman nature. The dichotomy of nature and culture then lines up to "a seemingly endless series of human exclusions" (Moore, Introduction 2) and alienates humans from nature. In these plays, a random disgusting object functions as substitute for the border between humans and nature. By making toy polar bears or foxes disgusting, the border between humans and nature, and to some extent between humans and other humans, is redrawn, which leads to an increased sense of isolation and alienation. Therefore, both plays use disgust as a technique to extrapolate the lack of interconnection between humans and nature, which comments on the competitive, isolating, and destructive nature of the Capitalocene. [ABSTRACT FROM AUTHOR]

Background: In changing northern ecosystems, understanding the mechanisms of transmission of zoonotic pathogens, including the coccidian parasite Toxoplasma gondii, is essential to protect the health of vulnerable animals and humans. As high-level predators and scavengers, foxes represent a potentially sensitive indicator of the circulation of T. gondii in environments where humans co-exist. The objectives of our research were to compare serological and molecular assays to detect T. gondii, generate baseline data on T. gondii antibody and tissue prevalence in foxes in northern Canada, and compare regional seroprevalence in foxes with that in people from recently published surveys across northern Canada. Methods: Fox carcasses (Vulpes vulpes/Vulpes lagopus, n = 749) were collected by local trappers from the eastern (Labrador and Québec) and western Canadian Arctic (northern Manitoba, Nunavut, and the Northwest Territories) during the winters of 2015–2019. Antibodies in heart fluid were detected using a commercial enzyme-linked immunosorbent assay. Toxoplasma gondii DNA was detected in hearts and brains using a magnetic capture DNA extraction and real-time PCR assay. Results: Antibodies against T. gondii and DNA were detected in 36% and 27% of foxes, respectively. Detection of antibodies was higher in older (64%) compared to younger foxes (22%). More males (36%) than females (31%) were positive for antibodies to T. gondii. Tissue prevalence in foxes from western Nunavik (51%) was higher than in eastern Nunavik (19%). At the Canadian scale, T. gondii exposure was lower in western Inuit regions (13%) compared to eastern Inuit regions (39%), possibly because of regional differences in fox diet and/or environment. Exposure to T. gondii decreased at higher latitude and in foxes having moderate to little fat. Higher mean infection intensity was observed in Arctic foxes compared to red foxes. Fox and human seroprevalence showed similar trends across Inuit regions of Canada, but were less correlated in the eastern sub-Arctic, which may reflect regional differences in human dietary preferences. Conclusions: Our study sheds new light on the current status of T. gondii in foxes in northern Canada and shows that foxes serve as a good sentinel species for environmental circulation and, in some regions, human exposure to this parasite in the Arctic. [ABSTRACT FROM AUTHOR]

Vulpesare widely distributed throughout the world and have undergone drastic physiological and phenotypic changes in response to their environment. However, little is known about the underlying genetic causes of these traits, especially Vulpes corsac. In this study, RNA‐Seq was used to obtain a comprehensive dataset for multiple pooled tissues of corsac fox, and selection analysis of orthologous genes was performed to identify the genes that may be influenced by the low‐temperature environment. More than 6.32 Gb clean reads were obtained and assembled into a total of 173,353 unigenes with an average length of 557 bp for corsac fox. Selective pressure analysis showed that 16 positively selected genes (PSGs) were identified in corsac fox, red fox, and arctic fox. Enrichment analysis of PSGs showed that the LRP11 gene was enriched in several pathways related to the low‐temperature response and might play a key role in response to environmental stimuli of foxes. In addition, several positively selected genes were related to DNA damage repair (ELP2 and CHAF1A), innate immunity (ARRDC4 and S100A12), and the respiratory chain (NDUFA5), and these positively selected genes might play a role in adaptation to harsh wild fox environments. The results of common orthologous gene analysis showed that gene flow or convergent evolution might be an important factor in promoting regional differentiation of foxes. Our study provides a valuable transcriptomic resource for the evolutionary history of the corsac fox and the adaptations to the extreme environments. [ABSTRACT FROM AUTHOR]

For the conservation and management of the Arctic regions vulnerable to climate change, it is important to elucidate the trophic relations and food sources for consumers in the ecosystems. We analyzed DNA extracted from feces to understand the summer diets of the major terrestrial animals and their trophic relations in tundra ecosystems near Kongsfjorden, Svalbard. Feces of Svalbard reindeer (Rangifer tarandus platyrhynchus), Barnacle Goose (Branta leucopsis), Arctic fox (Vulpes lagopus), and Rock Ptarmigan (Lagopus muta) were collected during the summer seasons of 2014, 2015, 2018, and 2019. Plant DNA was detected in the feces of herbivores (reindeer, goose, and ptarmigan) and vertebrate DNA was detected in the feces of carnivore (Arctic fox) by amplifying, cloning, and Sanger sequencing. In case of Arctic fox, VulpesB, the blocking primer preventing from amplifying Arctic fox DNA, was used to improve the detection of their prey DNA. Salix was the most detected genus in feces of Svalbard reindeer and Barnacle Goose, which were described as feeding on graminoids, forbs, and prostrate as well as bryophyte. Bryophyte was added as an important food source for all herbivores. Arctic fox preferred birds such as geese (Anatidae) and gulls (Laridae), showing that interpretation between Arctic foxes and gulls may have occurred at the same predator level. Our results suggest that cloning-based DNA analysis using fecal sample contributes to understanding the tundra terrestrial food web near Kongsfjorden. [ABSTRACT FROM AUTHOR]

We evaluated patterns of herbivory and predation/scavenging by a small mammal, the arctic ground squirrel (Urocitellus parryii), as an indicator of biological diversity, vegetation structure, and ecological integrity on two contrasting islands in the vast and remote Alaska Maritime National Wildlife Refuge. Using DNA metabarcoding techniques, we assessed the taxonomic composition of vertebrates, vascular plants, and bryophytes at family and growth form levels in arctic ground squirrel fecal samples collected on the ecologically intact island of Chowiet, which supports diverse seabird and vegetation communities, and the degraded island of Chirikof, which has incurred centuries of disturbance from introduced arctic fox (Vulpes lagopus) and cattle (Bos taurus taurus). We also evaluated whether fecal samples collected across the growing season (May—August) could act as indicators of herbivore-plant phenology. We did not detect any vertebrate taxa, however, observed herbivory patterns closely matched known differences in island plant diversity based on independent surveys. Diets from the ecologically intact island exhibited higher taxonomic richness, greater evenness, and higher shrub content than the ecologically degraded island, which is a grass- and forb-dominated ecosystem. On Chowiet Island, diets changed seasonally, likely in response to changing availability, nutritional quality, and toxin content associated with primary production. Small mammal diet served as an effective indicator of plant diversity, vegetation structure, and ecological integrity when compared against known composition and status of these remote island ecosystems. Non-invasive fecal sampling and dietary analyses using genetic techniques may provide a useful strategy for monitoring biological diversity, particularly in remote areas where widespread intensive sampling is unfeasible. [ABSTRACT FROM AUTHOR]

Parasitic zoonotic nematodes of the genus Trichinella circulate in wildlife and domestic hosts worldwide through the ingestion of infected meat. Due to their role as scavengers and predators in terrestrial and marine arctic ecosystems, Arctic foxes (Vulpes lagopus) are ideal sentinels for the detection of Trichinella spp. In this study, we determined the prevalence, larval intensity, and species of Trichinella from 91 trapped Arctic foxes collected around the northern Canadian communities of Sachs Harbour (Ikaahuk) on Banks Island (n = 23), and Ulukhaktok and Cambridge Bay (Ikaluktutiak) on Victoria Island (n = 68). Using pepsin-HCl digestion, larvae of Trichinella spp. were recovered from the left forelimb muscle (flexor carpi ulnaris) in 19 of the 91 foxes (21% prevalence, 95% CI: 14–30%). For the first time in Arctic foxes in Canada, Trichinella species were identified using multiplex PCR that was followed up with PCR-RFLP to distinguish between T. nativa and T. chanchalensis. All infected foxes harbored T. nativa, and one fox was co-infected with Trichinella T6; the latter is a new host record. Age of the fox was significantly associated with Trichinella spp. infection and the odds of being infected were three times higher in foxes ≥2 years of age (p = 0.026), indicating cumulative exposure with age. While Arctic foxes are seldom harvested for human consumption, they serve as sentinel hosts of Trichinella spp., confirming the presence of the parasite in wildlife in the region.

In socially flexible species, the tendency to live in groups is expected to vary through a trade-off between costs and benefits, determined by ecological conditions. The Resource Dispersion Hypothesis predicts that group size changes in response to patterns in resource availability. An additional dimension is described in Hersteinsson's model positing that sociality is further affected by a cost–benefit trade-off related to predation pressure. In the arctic fox (Vulpes lagopus), group-living follows a regional trade-off in resources' availability and intra-guild predation pressure. However, the effect of local fluctuations is poorly known, but offers an unusual opportunity to test predictions that differ between the two hypotheses in systems where prey availability is linked to intra-guild predation. Based on 17-year monitoring of arctic fox and cyclic rodent prey populations, we addressed the Resource Dispersion Hypothesis and discuss the results in relation to the impact of predation in Hersteinsson's model. Group-living increased with prey density, from 7.7% (low density) to 28% (high density). However, it remained high (44%) despite a rodent crash and this could be explained by increased benefits from cooperative defence against prey switching by top predators. We conclude that both resource abundance and predation pressure are factors underpinning the formation of social groups in fluctuating ecosystems. [ABSTRACT FROM AUTHOR]

We propose an ecogenetic model of "prey–predator" community with predator fitness determined genetically by a single autosomal diallelic pleiotropic locus in the case of diploid population. Predator genotypes with different reproductive potential are unequally adapted to food resource limitation; therefore, the fitness of a predator's genotype is determined by not only its own genotype but also the prey numbers. We use discrete-time equations for modeling, which allows considering features of the community species lifecycle. The paper extends our previous studies modeling evolution of a local population to explain existing genetic diversity by litter size in various (natural and farmed) populations of Arctic foxes (Alopex lagopus). Direct inclusion of prey population dynamics in the model of community allows analyzing polymorphism maintenance in arctic fox populations under more realistic conditions. As in simpler models, the direction of evolution of the predator population is shown to be generally determined by the relative position of its genotype fitnesses, whereas the parameter set characterizing birth rates of the prey and the predator, as well as the characteristics of interspecific interaction, determines the dynamic mode of interacting species numbers. However, even without overdominance, a predator can maintain a stable polymorphism owing to large-amplitude fluctuations in the number of prey, which change the direction of natural selection in the predator population. Different dynamics in the genetic composition of the predator can lead to a change in the dynamic mode of the prey numbers. [ABSTRACT FROM AUTHOR]

Arctic foxes (Vulpes lagopus) are susceptible to smooth Brucella (s-Brucella) infection and may be exposed to such bacteria through the consumption of infected marine mammals, as implied by the finding of s-Brucella antibodies in polar bears (Ursus maritimus). Arctic foxes in Svalbard have not previously been investigated for s-Brucella antibodies, but such antibodies have been detected in Arctic foxes in Iceland, Alaska (USA) and Russia. We investigated blood from Svalbard Arctic foxes for s-Brucella antibodies using an indirect enzyme-linked immunosorbent assay (iELISA). The animals (0-13 years old) were either caught by fur trappers (1995-2003, n = 403) or found dead (1995 and 2003, n = 3). No seropositive animals were detected. Morbidity and mortality due to the infection cannot be ruled out. However, no known, large disease outbreaks of unknown aetiology have been reported. Furthermore, it is unlikely that the Svalbard Arctic fox is resistant to infection as Arctic foxes from other populations are susceptible, and there is circumpolar connectivity between populations. The discrepancy between the findings in Iceland and Svalbard is surprising as both populations are on islands with no known local sources of exposure to s-Brucella other than marine mammals. However, our negative findings suggest that marine mammals may not be a major source of infection for this species. Comparative investigations are needed in order to draw conclusions regarding the epizootiology of s-Brucella in Arctic foxes in Svalbard and Iceland. [ABSTRACT FROM AUTHOR]

The Arctic foxes, Vulpes lagopus, from the Commander Islands are known to be well differentiated in skull morphology from the mainland population. Our study is the first to compare this differentiation with interspecies variations in the family Canidae. The level of skull variations between the Arctic foxes of the Commander Islands and the mainland Arctic fox was compared with skull variations between (1) the gray fox, Urocyon cinereoargenteus, and the island fox, U. littoralis; and (2) three closely related species of the Arctic fox: the swift fox, V. velox, and the kit fox, V. macrotis. The skull variations between the Arctic foxes of the Commander Islands and the mainland Arctic fox were shown to correspond to the interspecies level of skull variation in sister species of the genera Vulpes and Urocyon. No general trend in skull variation has been found between the species studied and isolated populations. The craniological data presented support the separation of foxes from the Commander Islands as a distinct species, V. beringensis Merriam 1902, with two subspecies: V. b. semenovi Ognev 1931 (Medny Island) and V. b. beringensis Merriam 1902 (Bering Island). The Arctic foxes of the Commander Islands are a unique part of the biological diversity and must be strictly protected. [ABSTRACT FROM AUTHOR]

Climate-caused changes in prey abundance may alter predator–prey dynamics in the Arctic food web. Lemmings (Dicrostonyx spp.) are important prey for Arctic foxes (Vulpes lagopus) and their annual population fluctuations drive fox reproduction, creating strongly linked predator–prey population cycles. Winter diet directly impacts Arctic fox reproductive success, but winter prey diversity on the tundra is low. Strategies such as using the marine environment to scavenge seals have allowed Arctic foxes to persist during years of low lemming abundance. However, warming winters have decreased snowpack quality, preventing lemmings from reaching their previous high abundances, which may reduce their impact on predator dynamics. We investigated Arctic fox dietary response to lemming abundance by reconstructing Arctic fox winter diet in the low Arctic. Next-generation sequencing of fecal DNA, from samples (n = 627) collected at dens in winters of 2011–2018, identified prey both from terrestrial and marine environments. Despite lemming cycle damping, Arctic foxes still increased lemming consumption during years of higher lemming abundance. Alternative prey such as marine resources were consumed more during years of low lemming abundance, with up to 45% of samples containing marine resources in low lemming years. In addition, Arctic foxes consumed high proportions of meadow voles (Microtus pennsylvanicus), which may represent a new alternative prey, suggesting climate change may be creating new foraging opportunities. Changes in prey abundance illustrate how climate-caused disturbances are altering Arctic food-web dynamics. Dietary flexibility and availability of alternative prey may become increasingly important for Arctic predators as the Arctic continues to change. [ABSTRACT FROM AUTHOR]

The present study investigated the effects of lysine supplementation in low-protein diets on nutrients digestibility, growth performance and healthy status of growing female blue foxes (Alopex lagopus). Control animals were fed a diet containing normal protein level (32% of dry matter, DM). Animals in the treatment groups were challenged with lowprotein diets supplemented with 0.00%, 0.20%, 0.40%, 0.60%, 0.80% and 1.00% lysine, corresponding to 0.87%, 1.07%, 1.27%, 1.47%, 1.67% and 1.87% total lysine of DM, respectively. Results showed that 1.47% lysine supplementation exerted beneficial effects (P < 0.05) on blue foxes, as evidenced by improved digestibility of crude protein (CP) and several amino acids (aspartic acid, glycine, methionine, isoleucine and tyrosine). Similar effect was observed in N retention (P < 0.05) and the growth performance (P < 0.05). Additionally, the 0.87% lysine group exhibited a significant decrease in blood albumin (ALB) as opposed to the other groups (P < 0.01). Collectively, these findings indicate that quality of low-protein diet can be improved by supplemented lysine without influencing health of female blue foxes at the growing phase. The optimum lysine for maximum performance and low N emission of the growing female blue foxes in approximately 1.47% of DM. [ABSTRACT FROM AUTHOR]

Predation shapes communities through consumptive and non‐consumptive effects. In the latter case, prey respond to perceived predation risk through proactive or reactive risk management strategies occurring at different spatial and temporal scales. The predator–prey space race and landscape of fear concepts are useful to better understand how predation risk affects prey behavioral decisions and distribution. We assessed predation risk effects in a terrestrial Arctic community, where the arctic fox is the main predator of ground‐nesting birds. Using high‐frequency GPS data, we estimated a predator activity landscape corresponding to fox space use patterns and validated with an artificial prey experiment that this predator activity landscape correlated with the predation risk landscape. We then investigated the effects of the fox activity landscape on multiple prey species, by assessing the anti‐predator behavior of a main prey (snow goose) actively searched for by foxes, and the nest distribution of several incidental prey species. We first found that snow geese showed a stronger level of nest defense in areas highly used by foxes, possibly responding with a reactive strategy to variation in predation risk. Then, nests of incidental prey reproducing in habitats easily accessed by foxes had a lower probability of occurrence in areas highly used by foxes, suggesting these birds may use a proactive risk management strategy by shifting their distribution away from risky areas. For incidental prey species nesting in microhabitat refuges difficult to access by foxes, probability of nest occurrence was independent of predation risk in the surrounding area, as they avoid risk at a finer spatial scale. By tracking all individuals of the dominant predator species in our study area, we demonstrated the value of using predator space use patterns to infer spatial variation in predation risk. Overall, we highlight the diversity of risk management strategies in prey sharing a common predator, hence refining our understanding of the mechanisms driving species distribution and community structure. [ABSTRACT FROM AUTHOR]

Selecting the right location for a den during the breeding season is a type of habitat selection in the Arctic fox (Vulpes lagopus) that is likely to affect its reproductive success. A den's suitability likely depends on its ability to provide shelter, as well as its proximity to prey resources. Depending on the different relative risks that Arctic foxes may face across their broad circumpolar range, Arctic foxes may place different emphases on selection for shelter and prey resources in different ecosystems. Understanding the different requirements for reproduction under different ecological conditions is highly relevant to conservation efforts in areas where Arctic foxes are threatened by rapid environmental changes. Here, we investigated the relative selection for shelter and prey resources in southern Yamal Peninsula (Russia) using data from 45 dens collected over a 13-year period. Arctic foxes preferred to breed in dens with more den entrances; an indicator of shelter quality. Arctic foxes also preferred dens surrounded by more prey resources (quantified by the amount of river valley habitat), but this result was less conclusive. These results complement the findings reported from other study areas, illustrating that Arctic foxes in ecosystems with diverse predator communities may put emphasis on selection for shelter quality. In less productive ecosystems, Arctic foxes may rather put emphasis on selection for prey resources. As tundra ecosystems become more productive and generalist predators move north, the reproductive requirements and habitat selection of Arctic foxes may change accordingly, depending on the species' ability to adapt. [ABSTRACT FROM AUTHOR]

Abstract Background In a warmer and more globally connected Arctic, vector-borne pathogens of zoonotic importance may be increasing in prevalence in native wildlife. Recently, Bartonella henselae, the causative agent of cat scratch fever, was detected in blood collected from arctic foxes (Vulpes lagopus) that were captured and released in the large goose colony at Karrak Lake, Nunavut, Canada. This bacterium is generally associated with cats and cat fleas, which are absent from Arctic ecosystems. Arctic foxes in this region feed extensively on migratory geese, their eggs, and their goslings. Thus, we hypothesized that a nest flea, Ceratophyllus vagabundus vagabundus (Boheman, 1865), may serve as a vector for transmission of Bartonella spp. Methods We determined the prevalence of Bartonella spp. in (i) nest fleas collected from 5 arctic fox dens and (ii) 37 surrounding goose nests, (iii) fleas collected from 20 geese harvested during arrival at the nesting grounds and (iv) blood clots from 57 adult live-captured arctic foxes. A subsample of fleas were identified morphologically as C. v. vagabundus. Remaining fleas were pooled for each nest, den, or host. DNA was extracted from flea pools and blood clots and analyzed with conventional and real-time polymerase chain reactions targeting the 16S-23S rRNA intergenic transcribed spacer region. Results Bartonella henselae was identified in 43% of pooled flea samples from nests and 40% of pooled flea samples from fox dens. Bartonella vinsonii berkhoffii was identified in 30% of pooled flea samples collected from 20 geese. Both B. vinsonii berkhoffii (n = 2) and B. rochalimae (n = 1) were identified in the blood of foxes. Conclusions We confirm that B. henselae, B. vinsonii berkhoffii and B. rochalimae circulate in the Karrak Lake ecosystem and that nest fleas contain B. vinsonii and B. henselae DNA, suggesting that this flea may serve as a potential vector for transmission among Arctic wildlife.