Physiological adaptations to fasting in an actively wintering canid, the Arctic blue fox (Alopex lagopus)

This study investigated the physiological adaptations to fasting using the farmed blue fox (Alopex lagopus) as a model for the endangered wild arctic fox. Sixteen blue foxes were fed throughout the winter and 32 blue foxes were fasted for 22 d in Nov-Dec 2002. Half of the fasted blue foxes were food-deprived again for 22 d in Jan-Feb 2003. The farmed blue fox lost weight at a slower rate (0.97-1.02% body mass d(-1)) than observed previously in the arctic fox, possibly due to its higher initial body fat content. The animals experienced occasional fasting-induced hypoglycaemia, but their locomotor activity was not affected. The plasma triacylglycerol and glycerol concentrations were elevated during phase II of fasting indicating stimulated lipolysis, probably induced by the high growth hormone concentrations. The total cholesterol, HDL- and LDL-cholesterol, urea, uric acid and total protein levels and the urea:creatinine ratio decreased during fasting. Although the plasma levels of some essential amino acids increased, the blue foxes did not enter phase III of starvation characterized by stimulated proteolysis during either of the 22-d fasting procedures. Instead of excessive protein catabolism, it is liver dysfunction, indicated by the increased plasma bilirubin levels and alkaline phosphatase, alanine aminotransferase and aspartate aminotransferase activities, that may limit the duration of fasting in the species.     

Prevalence and geographical distribution of the ear canker mite (Otodectes cynotis) among arctic foxes (Alopex lagopus) in Iceland

Three hundred forty five adult arctic foxes (Alopex lagopus) from all counties in Iceland were examined for excess cerumen and ear canker mites (Otodectes cynotis). Only 13 foxes (4%) from a single county in northwestern Iceland were infested, where the prevalence of otodectiasis was 38%. Whether or not this parasite is new to the arctic fox in Iceland is unknown. If it is recently introduced, possible sources of infestation are farmed silver foxes (Vulpes vulpes), domestic dogs, domestic or feral cats, and arctic foxes from Greenland. It appears that the rate of transmission between adult foxes is low; a more common route of transmission is probably from the mother to her offspring or between vixens breeding in the same dens in subsequent years by contamination of the dens. No correlation was found between the prevalence of mites in foxes and Samson character.     

Ileal and total tract nutrient digestibility in blue foxes (Alopex lagopus) fed extruded diets containing different protein sources

This study compared apparent ileal and total tract digestibility of macronutrients and amino acids in blue foxes (Alopex lagopus) fed dry extruded diets. The control diet contained fish meal as the main protein source, while in the other diets 50% of the fish meal protein was replaced by not de-hulled solvent-extracted soybean meal, meat meal or bacterial protein meal. Ileal digestibility was obtained with animals modified with ileorectal anastomosis (IRA method). There were no significant differences in the average digestibility of CP, Lys, Trp, Val, Ala or Glu between IRA modified and intact animals. Average ileal digestibilities of His, Thr, Asp, Cys, Gly, Hyp, Pro, Ser, starch and total carbohydrates (CHO) were significantly lower compared with total tract values. Average ileal digestibility of Arg, Ile, Leu, Met, Phe, Tyr and crude fat was significantly higher than total tract digestibility. Digestibility measured in IRA modified animals showed less variability compared with values from intact animals. There were significant differences among diets in ileal as well as total tract digestibility of orude protein, most amino acids, starch and CHO, and in ileal digestibility of crude fat. Ileal crude protein digestibility of the diets ranged from 81.0-86.4% and total tract digestibility from 82.5-86.4%. Ileal amino acid digestibilities ranged from 70.1 (Asp) to 93.3% (Arg) and total tract values ranged from 72.8 (Cys) to 92.2% (Arg). Both ileal and total tract digestibilities of crude protein and most amino acids were significantly lower for diets containing meat meal or bacterial protein meal compared with the control fish meal-based diet and the diet with soybean meal. Although ileal digestibility may be more accurate than total tract digestibility in estimating the protein and amino acid supply in blue foxes, total tract digestibility may be acceptable because of numerically small differences between ileal and total tract digestibilities for protein and most amino acids. It was further concluded that ileal digestibilities of starch and CHO in the blue fox are lower than corresponding total tract digestibilities.     

Inheritance of litter size at birth in farmed arctic foxes (Alopex lagopus, Canidae, Carnivora)

Natural populations of the arctic fox (Alopex lagopus, Canidae, Carnivora) differ drastically in their reproductive strategy. Coastal foxes, which depend on stable food resources, produce litters of moderate size. Inland foxes feed on small rodents, whose populations are characterized by cycling fluctuation. In the years with low food supply, inland fox populations have a very low rate of reproduction. In the years with high food supply, they undergo a population explosion. To gain insight into the genetic basis of the reproductive strategy of this species, we performed complex segregation analysis of the litter size in the extended pedigree of the farmed arctic foxes involving 20,665 interrelated animals. Complex segregation analysis was performed using a mixed model assuming that the trait was under control of a major gene and a large number of additive genetic and random factors. To check the significance of any major gene effect, we used Elston-Stewart transmission probability test. Our analysis demonstrated that the inheritance of this trait can be described within the frameworks of a major gene model with recessive control of low litter size. This model was also supported by the pattern of its familial segregation and by comparison of the distributions observed in the population and that expected under our model. We suggest that a system of balanced polymorphism for litter size in the farmed population might have been established in natural populations of arctic foxes as a result of adaptation to the drastic fluctuations in prey availability.     

Adiponectin and peptide YY in the fasting blue fox (Alopex lagopus)

Adiponectin (Acrp30) and peptide YY (PYY) are weight-regulatory hormones participating in the control of energy homeostasis. This study investigated the effects of long-term wintertime fasting on plasma Acrp30 and PYY levels in the carnivorous blue fox, a farm-bred variant of the arctic fox (Alopex lagopus). Plasma Acrp30 and PYY concentrations were determined with radioimmunoassays during a 22-day period of fasting, which led to a 20.3% reduction in body mass of the animals (n=32). Sixteen fed blue foxes served as the control group. Acrp30 and PYY were present in blue fox plasma at similar or lower levels as reported previously for other mammals. Fasting had no acute effects on Acrp30 or PYY concentrations of the blue foxes. However, the Acrp30 levels of the fasted blue foxes were 24%-48% higher than in the fed animals between days 8-22 of fasting. Fasted blue foxes also had 6.2-fold higher plasma PYY concentrations after 15 days of fasting. Acrp30 and PYY seem to play roles in the body weight-regulation of the blue fox during long-term fasting, but their specific functions and physiological significance remain to be determined.     

Two cysteine substitutions in the MC1R generate the blue variant of the Arctic fox (Alopex lagopus) and prevent expression of the white winter coat

We have characterized two mutations in the MC1R gene of the blue variant of the arctic fox (Alopex lagopus) that both incorporate a novel cysteine residue into the receptor. A family study in farmed arctic foxes verified that the dominant expression of the blue color phenotype cosegregates completely with the allele harboring these two mutations. Additionally to the altered pigment synthesis, the blue fox allele suppresses the seasonal change in coat color found in the native arctic fox. Consequently, these findings suggest that the MC1R/agouti regulatory system is involved in the seasonal changes of coat color found in arctic fox.     

Diet of arctic foxes (Alopex lagopus) in Iceland

Arctic foxes, Alopex lagopus , live in low productivity arctic and northern tundra habitats, where they generally prey heavily on lemmings. In Iceland, however, no lemmings are present, and the foxes have a very varied diet, including plants such as seaweed and black crowberries, a wide range of birds and invertebrates, and carcasses of large mammals such as seals, reindeer, and sheep. Marked seasonal, geographical and inter-annual differences confirm arctic foxes in Iceland as opportunistic feeders. There are coastal and inland foxes: coastal foxes feed mainly on prey derived directly or indirectly from the ocean, particularly various seabirds and seals, while inland foxes feed largely on migrant birds, such as geese, waders and passerines in summer, and ptarmigan in winter. Despite their reputation for killing lambs, in this study, lamb carcasses were found at only 19.4% of 1125 fox dens, 44% of which had only one carcass. The distance to the nearest farm and the physical condition of lambs were major determinants of the number of carcasses found at a den. We discuss the implications of arctic foxes' diet for population dynamics and group formation, and for management practices.     

Immunization of arctic foxes (Alopex lagopus) with oral rabies vaccine

Arctic foxes (Alopex lagopus) were successfully immunized against rabies using an orally-administered, liquid SAD-BHK21 live virus vaccine in a sausage bait. Immunization was determined by serologic response and by resistance to challenge with an arctic rabies virus strain. Virus was not shed in saliva following oral vaccination, indicating that arctic foxes would not infect other foxes after ingesting this vaccine. High antibody levels were present in all experimental foxes 2 wk following initial vaccination. A booster vaccination at 56 wk induced a significant serologic response within 1 wk, suggesting an anamnestic response but titers began to decline within 8 wk in most foxes. Foxes were observed for 16 mo following the challenge and exhibited no symptoms of rabies. The SAD-BHK21 rabies vaccine in a sausage bait system has a strong potential for vaccinating wild populations of arctic fox.     

Comparative aspects of sperm membrane fatty acid composition in silver (Vulpes vulpes) and blue (Alopex lagopus) foxes, and their relationship to cell cryopreservation

Cryogenic protocols have been developed for the storage of farmed silver fox (Vulpes vulpes) spermatozoa. However, these same protocols and modifications of these protocols have failed to satisfactorily preserve spermatozoa collected from farmed blue foxes (Alopex lagopus). Because cryogenic success has been linked to membrane composition, the plasma membrane lipid composition of farmed blue fox and silver fox spermatozoa was studied. Silver fox spermatozoal membranes have significantly higher levels of docosapentaenoic acid (DPA; 22:5, n-6) compared to blue fox spermatozoa, and blue fox spermatozoal membranes have significantly higher levels of stearic acid (18:0). Silver fox spermatozoal membranes not only have a higher ratio of unsaturated/saturated membrane fatty acids, but also higher levels of membrane desmosterol and cholesterol.     

Preference for various nest box designs in farmed silver foxes (Vulpes vulpes) and blue foxes (Alopex lagopus)

Nest box choice experiments were carried out outside the breeding season on adult silver and blue fox vixens with no previous permanent nest box experience. Nest boxes were varied in height of placement, number of rooms, presence of entrance room or platform and light conditions. Only one parameter was varied in any one experiment. Both fox species clearly preferred an elevated multi-room nest box; while silver foxes showed preference for boxes supplied with a platform, blue foxes preferred boxes with an entrance room. There was no significant box preference with respect to light conditions. The possible welfare implications of the preferences are discussed.     

First Characterization in China of Encephalitozoon cuniculi in the Blue Fox (Alopex lagopus)

Encephalitozoon cuniculi is a microsporidian parasite that infects a wide range of vertebrates, including primates. It has recently emerged as an opportunistic parasite of patients infected with the human immunodeficiency virus. The blue fox (Alopex lagopus; also known as the arctic fox) is one of the most susceptible species for encephalitozoonosis. Here, we report an outbreak of encephalitozoonosis at a fox farm in China. The isolated parasites displayed the typical morphology of E. cuniculi as assessed by Masson's trichrome staining. Analysis of the internal transcribed spacer sequence indicated that the isolated parasite is a genotype III strain of E. cuniculi. Furthermore, phylogenetic analysis of the PTP1 gene verifies classification of this new strain (termed LN‐1) with other genotype III E. cuniculi strains, though the PTP3 and SWP1 sequences diverge from the reference strain. This is the first report of encephalitozoonosis in farmed blue foxes in China.     

Survey for Encephalitozoon cuniculi in arctic foxes (Alopex lagopus) in Greenland

Wild arctic foxes (Alopex lagopus) from Greenland were tested for antibodies to Encephalitozoon cuniculi with an enzyme-linked immunosorbent assay and a carbon immunoassay. Of 230 tested foxes none was seropositive. This finding contrasts with observations from other arctic areas and absence of rodents in the diet of these arctic foxes is the most likely explanation for absence of E. cuniculi.     

Dietary variation in arctic foxes (Alopex lagopus)-an analysis of stable carbon isotopes

We used stable carbon isotopes to analyse individual variation in arctic fox diet. We extracted collagen from bones (the lower jaw), and measured stable carbon isotopes. The foxes came from three different localities: Iceland, where both microtines and reindeer are rare; west Greenland, where microtines are absent; and Sweden, where scat analyses showed the primary food to be microtine rodents and reindeer. The Icelandic samples included foxes from both coastal and inland habitats, the Swedish sample came from an inland area, and the Greenland sample from coastal sites. The spatial variation in the isotopic pattern followed a basic division between marine and terrestrial sources of protein. Arctic foxes from inland sites had ¹³C values of –21.4 (Iceland) and –20.4 (Sweden), showing typical terrestrial values. Coastal foxes from Greenland had typical marine values of –14.9, whereas coastal foxes from Iceland had intermediate values of –17.7. However, there was individual variation within each sample, probably caused by habitat heterogeneity and territoriality among foxes. The variation on a larger scale was related to the availability of different food items. These results were in accordance with other dietary analyses based on scat analyses. This is the first time that stable isotopes have been used to reveal individual dietary patterns. Our study also indicated that isotopic values can be used on a global scale.     

Inter- and intraspecific competition between the fox species Alopex lagopus and Vulpes vulpes: an evaluation trial under penned conditions

This study compared competition capacity and dominance relations between arctic foxes (Alopex lagopus) and red foxes (Vulpes vulpes). Experiments were carried out in semi-natural earthen floor enclosures using farm-bred colour types of both species (blue fox and silver fox) as subjects. Results of the dominance scoring and open field behaviour after weaning in August-September showed that blue foxes dominated over silver foxes. Thereafter, the situation gradually became reversed and silver foxes were dominant during the breeding and whelping seasons. Housing both species together from weaning produced more curious animals as compared to when these species were placed in common quarters after the autumn equinox. In the case of blue foxes, the male dominated highly over all females. In silver foxes, the difference in dominance between the sexes was, however, less pronounced. The most dominant individuals in the study groups were typically among the heaviest. Breedings and whelpings succeeded better in silver than in blue foxes. However, none of litters born survived more than one week. The present results support the conclusion that when both fox species are housed together, Vulpus vulpus tends to dominate over Alopex lagopus. Received: 22 March 1996/Accepted: 30 June 1996     

Effects of fasting and exogenous melatonin on annual rhythms in the blue fox (Alopex lagopus)

The arctic fox (Alopex lagopus) is a winter-active inhabitant of the high arctic with extreme fluctuations in photoperiod and food availability. The blue fox is a semi-domesticated variant of the wild arctic fox reared for the fur industry. In this study, 48 blue foxes were followed for a year in order to determine the effects of exogenous melatonin and wintertime food deprivation on their reproductive and thyroid axes. Half of the animals were treated with continuous-release melatonin capsules in July 2002, and in November-January, the animals were divided into three groups and either fed continuously or fasted for one or two 22-day periods. Food deprivation decreased the plasma triiodothyronine and thyroxine concentrations probably in order to preserve energy due to a decreased metabolic rate. The same was observed in the plasma testosterone levels of the males but not in the plasma estradiol concentrations of the females. Exogenous melatonin advanced the autumn moult and seasonal changes in the voluntary food intake. It also advanced the onset of the testosterone peak in the males. The plasma estradiol levels of the females were unaffected, but the progesterone levels peaked more steeply in the sham-operated females. Melatonin exerted a strong influence not only on the reproductive axis of the males but also on the seasonal food intake. The species seemed quite resistant to periodic involuntary food deprivation.     

Prevalence of Toxoplasma gondii infection diagnosed by PCR in farmed red foxes, arctic foxes and raccoon dogs

The aim of this study was to compare Toxoplasma gondii infection in three canid species: red fox Vulpes vulpes, arctic fox Vulpes lagopus and raccoon dog Nyctereutesprocyonoides kept at the same farm. Anal swabs were taken from 24 adult and 10 juvenile red foxes, 12 adult arctic foxes, three adult and seven juvenile raccoon dogs. Additionally, muscle samples were taken from 10 juvenile red foxes. PCR was used to detect T. gondii DNA. T. gondii infection was not detected in any of the arctic foxes; 60% ofraccoon dogs were infected; the prevalence of the parasite in material from red fox swabs was intermediate between the prevalence observed in arctic foxes and raccoon dogs. It is possible that susceptibility and immune response to the parasite differ between the three investigated canid species. T. gondii DNA was detected in muscle tissue of five young foxes. The results of this study suggest that T. gondii infection is not rare in farmed canids.     

Genotyping of Enterocytozoon bieneusi in Farmed Blue Foxes (Alopex lagopus) and Raccoon Dogs (Nyctereutes procyonoides) in China

Enterocytozoon bieneusi is the most common species of microsporidia found both in humans and animals. Farmed animals, particularly closely associated to humans, may play an important role of zoonotic reservoir in transmitting this disease to humans. The fur industry is a major economic component in some parts of China. To understand the prevalence, genotype variety and zoonotic risk of E. bieneusi in farmed foxes and raccoon dogs, two species of fur animals, fecal specimens of 110 blue foxes and 49 raccoon dogs from Heilongjiang and Jilin provinces in China were examined by internal transcribed spacer (ITS)-based PCR. E. bieneusi was detected in 16.4% (18/110) blue foxes and 4.1% (2/49) raccoon dogs. Altogether, four genotypes of E. bieneusi were identified, including two known genotypes D (n = 13) and EbpC (n = 5), and two novel genotypes named as CHN-F1 (n = 1) in a fox and CHN-R1 (n = 1) in a raccoon dog. Phylogenetic analysis revealed that all the four genotypes were the members of zoonotic group 1. Genotypes D and EbpC were found in humans previously. The findings of zoonotic genotypes of E. bieneusi in the foxes and raccoon dogs suggest these animals infected with E. bieneusi may pose a threat to human health.     

Predator–prey relationships: arctic foxes and lemmings

1. The number of breeding dens and litter sizes of arctic foxes Alopex lagopus were recorded and the diet of the foxes was analysed during a ship-based expedition to 17 sites along the Siberian north coast. At the same time the cyclic dynamics of co-existing lemming species were examined.
2. The diet of arctic foxes was dominated by the Siberian lemming Lemmus sibiricus (on one site the Norwegian lemming L. lemmus ), followed by the collared lemming Dicrostonyx torquatus .
3. The examined Lemmus sibiricus populations were in different phases of the lemming cycle as determined by age profiles and population densities.
4. The numerical response of arctic foxes to varying densities of Lemmus had a time lag of 1 year, producing a pattern of limit cycles in lemming–arctic fox interactions. Arctic fox litter sizes showed no time lag, but a linear relation to Lemmus densities. We found no evidence for a numerical response to population density changes in Dicrostonyx .
5. The functional or dietary response of arctic foxes followed a type II curve for Lemmus , but a type III response curve for Dicrostonyx .
6. Arctic foxes act as resident specialist for Lemmus and may increase the amplitude and period of their population cycles. For Dicrostonyx , on the other hand, arctic foxes act as generalists which suggests a capacity to dampen oscillations.     

Home range and movements of arctic foxes Alopex lagopus in Svalbard

Summary Movements and home ranges of arctic foxes Alopex lagopus were studied in two regions of Svalbard by means of radio tracking (n= 17), ear tagging (n= 192) and visual observations. The movements of radio collared foxes were highly variable, and most foxes roamed over wide areas at least during periods of the year. Home range size was estimated for 11 foxes when more stationary and for three other less stationary foxes, and were in the range 5–120km². During non-stationary periods several foxes roamed over areas 500–1000 km² or more. These movements may more correctly be classified as nomadic, and should not be termed home ranges. Only 3 of 12 radio collarec. foxes that disappeared from an area, returned later. Seven of the 17 foxes were relocated to the same area in more than one season. Overlap of home ranges was extensive, even more so when a number of non-tagged foxes in the regions were included. The heavier juveniles and adults were more sedentary than those of weight lower than median.     

Dominance relations in captive groups of adult and juvenile arctic blue foxes (Alopex lagopus)

Dominance relationships were studied in captive Arctic blue fox (Alopex lagopus) groups comprising adults (four males, five females) and juveniles (four males, five females). The results showed that Arctic blue foxes easily formed a social organization with an observable hierarchy, in which adults typically dominated over juveniles. Within the same age group, males usually dominated over females. Dominance correlated most significantly with body weight in autumn, but later that correlation decreased. Urine marking activity was very low during autumn and early winter, but increased significantly prior to and during the breeding season when aggressive encounters were also most pronounced. In addition to several adults, the social status of some juveniles was high at breeding time. Altogether 7 out of 11 females (63.6%) whelped, but the survival rate of litters was low and kits of only two adult females survived (18.2%). It can be concluded that hierarchical development and reproduction in Arctic blue fox groups are markedly influenced by dominance relationships.