Comparative nutrient digestibility of arctic foxes (Alopex lagopus) on Svalbard and farm-raised blue foxes (Alopex lagopus)

Arctic foxes from Svalbard (n=4) and farmed blue foxes (n=4) was used in a digestibility experiment with a high-carbohydrate feed to add more information to the nutritional physiology of the arctic fox, and to compare its digestive capacity with that of the farmed blue fox. The arctic fox has a diet containing mainly protein and fat from mammals and birds, while farmed blue foxes have been exposed to an omnivorous dietary regime for more than 80 generations. The experiment showed in general no difference in digestive capacity for protein and fat between the foxes (P>0.05), but for carbohydrates, including starch and glucose, the blue fox revealed higher digestibility values. The superior digestive capacity for carbohydrates in blue fox might be a result of a long-term selection of animals digesting dietary carbohydrates more efficiently, or that an early age exposition to dietary carbohydrates has given permanent improvement of the carbohydrate digestion in the gut.     

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.     

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.     

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.     

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.     

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.     

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.     

Growth rates and energy demands in captive juvenile arctic foxes Alopex lagopus in Svalbard

Four arctic fox Alopex lagopus pups (two males and two females) were caught at dens when about 25–53 days old and kept in outdoor pens at NyÅlesund, Svalbard. Their growth in body size (as measured by the length of a front foot), increase in weight, and food consumption were monitored from July to December, 1987. The pups grew rapidly and reached 97.5 ± 0.1% of their maximum adult size when they were 99–127 days old. Increase in body weight took longer (130 days). Food consumption generally increased until about 90 days old, after which it was highly variable. Pups consumed on average 266 kcal kg^–1 day^–1 growing 34g/day until 95 days old. Subsequently, until about 200 days old, they consumed 202 kcal kg^–1 day^–1 and grew 6.8 g/day.     

Genetic polymorphism of adenosine deaminase and mannose phosphate isomerase in blood of arctic foxes, Alopex lagopus

Blood samples of 70 foxes, including 10 families, have been investigated by horizontal starch gel electrophoresis for the enzymes adenosine deaminase (ADA) and mannose phosphate isomerase (MPI). The observed variation of the enzymes could be explained as a result of one locus with two codominant alleles and one with three respectively. The segregation in the families of the alleles assumed for the two loci is in accordance with this genetic model. The frequency of the two alleles at the Ada locus is about the same and the slowest anodic migrating allele at the Mpi locus is the most frequent.     

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.     

Seasonal variations in basal metabolic rate, lower critical temperature and responses to temporary starvation in the arctic fox (Alopex lagopus) from Svalbard

Metabolic rates of four resting, post-absorptive male adult summer- and winter-adapted captive arctic foxes (Alopex lagopus) were recorded. Basal metabolic rates (BMR) varied seasonally with a 36% increase from winter to summer, while body mass was reduced by 17% in the same period. The lower critical temperature (T _1c) of the winter-adapted arctic fox was estimated to −7°C, whereas T _lc during summer was 5°C. The similarity of these values, which are much higher than hitherto assumed (e.g. Scholander et al. 1950b), is mainly due to a significantly (P<0.05) lower BMR in winter than in summer. Body core (stomach) temperature was stable, even at ambient temperatures as low as −45°C, but showed a significant (P<0.05) seasonal variation, being lower in winter (39.3±0.33°C) than in summer (39.8±0.16°C). The thermal conductivity of arctic fox fur was the same during both seasons, whereas the thermal conductance in winter was lower than in summer. This was reflected in an increase in fur thickness of 140% from summer to winter, and in a reduced metabolic response to ambient temperatures below T _lc in winter. Another four arctic foxes were exposed to three periods of forced starvation, each lasting 8 days during winter, when body mass is in decline. No significant reduction in mass specific BMR was observed during the exposure to starvation, and respiratory quotient was unchanged at 0.73±0.02 during the first 5 days, but dropped significantly (P<0.05) to 0.69±0.03 at day 7. Locomotor activity and body core (intraperitoneal) temperature was unaltered throughout the starvation period, but body mass was reduced by 18.5±2.1% during these periods. Upon re-feeding, locomotor activity was significantly (P<0.05) reduced for about 6 days. Energy intake was almost doubled, but stabilised at normal levels after 11 days. Body mass increased, but not to the level before the starvation episodes. Instead, body mass increased until it reached the reduced body mass of ad libitum fed control animals. This indicates that body mass in the arctic fox is regulated according to a seasonally changing set point.     

Genetic polymorphism of Commander Islands polar foxes Alopex lagopus semenovi Ognev, 1931 and Alopex lagopus beringiensis Merriam, 1902

The polymorphism of the mitochondrial DNA (mtDNA) control region sequence was examined in 30 polar foxes from Bering Island and 30 polar foxes from Mednyi Island. Seven haplotypes were revealed in polar foxes from Bering Island, and one, in polar foxes from Mednyi Island. The age of divergence of these populations (12 000 +/- 600 years) was calculated based on a fragment of the D-loop. In Bering polar foxes, the sequence nucleotide diversity (pi) was 0.003 (S.D. = 0.002), the haplotype diversity h in Bering polar foxes was 0.835 (S.D. = 0.037). The effective number of females n the Bering Island population was estimated as 105 animals.     

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.     

Seasonal trends in body mass, food intake and resting metabolic rate, and induction of metabolic depression in arctic foxes (Alopex lagopus) at Svalbard

 Post-absorptive resting metabolic rates (RMRs), body mass and ad libitum food intake were recorded on an annual cycle in captive arctic foxes (Alopex lagopus) at Svalbard. During the light season in May and in the dark period in November, RMR during starvation and subsequent re-feeding were also measured. In contrast to earlier findings, the present study indicated a seasonal trend in post-absorptive RMR (in W · kg⁻¹ and W · kg^−0.75). The values in the light summer were 15% and 11% higher than the values in the dark winter, suggesting a physiological adaptation aiding energy conservation during winter in arctic foxes. Body mass and ad libitum food intake varied inversely through the year. A significant reduction in RMR (in W and W · kg^−0.75) with starvation (metabolic depression) was recorded both in May and November, indicating an adaptation to starvation in arctic foxes. The lack of metabolic depression during a period of starvation that was concomitant with extremely cold ambient temperatures in November 1994 indicates that metabolic responses to starvation may be masked by thermoregulatory needs. At very low ambient temperatures, arctic foxes may require increased heat production which cannot be achieved via below-average rates of metabolism. Accepted: 7 June 1999     

Endoparasites in the endangered Fennoscandian population of arctic foxes (Vulpes lagopus)

The Fennoscandian arctic fox (Vulpes lagopus) population is endangered due to overharvest and competition with the larger red fox (Vulpes vulpes). In this study, we have screened the population in Sweden for endoparasites by analysis of non-invasively faecal samples collected at reproductive dens during two summers, one with low food abundance (2008) and the other with high food abundance (2010). Eggs, larvae and oocysts of a total of 14 different endoparasites were identified with a species richness per inhabited den of 3.2 (CI95% ± 0.48) in 2008 and 2.7 (CI95% ± 0.72) in 2010. Capillariidae-like eggs was identified at 59% of the dens in 2008 and 57% in 2010 and Toxocara canis with 7% (2008) and 30% (2010); Toxascaris leonina with 93% (2008) and 65% (2010); Uncinaria stenocephala 65% (2008) and 39% (2010); Crenosoma vulpis 3% (2008) and 4% (2010); Trichuris sp. 7% (2008) and 4% (2010); Cystoisospora canis-like oocysts 28% (2008) and 26% (2010); Cystoisospora ohiensis-like oocysts 38% (2008) and 4% (2010); Eimeria sp. 7% (2008) and 9% (2010); Sarcocystis sp. 3% (2008) and 9% (2010); Taenia sp. 10% (2008) and 4% (2010); Mesocestoides sp. 3% (2008) and 0% (2010); Balantidium sp. 0% (2008) and 9% (2010) and Spiruroidea-like eggs 0% (2008) and 4% (2010). To our knowledge, Balantidium sp., Sarcocystis sp. and Trichuris sp. has never been described before in wild arctic foxes.     

Wooden blocks and straw as environmental enrichments for juvenile blue foxes (Alopex lagopus)

This study was designed to evaluate the enrichment value of a wooden block (30 cm long×4 cm in diameter) and straw for growing farm-bred male blue foxes (Alopex lagopus). Comparisons were made between animals provided with these enrichments at 7 weeks and 15 weeks of age. Various behavioural, physiological, and haematological variables as well as fur and teeth characteristics were assessed. The foxes showed significantly higher motivation to interact with the block than with the straw. The novelty response to block manipulation was higher when the block was given to foxes at 15 weeks than at 7 weeks of age. In straw groups no actual age effect was observed. Both the wooden block and the straw appeared to stimulate particularly the occurrence of play behaviour, which can be considered an indicator of good welfare. Significant differences were not found between the experimental groups in the novel object (ball) in-cage test. However, a slight tendency for increased explorative activity and shorter latency to object sniffing in the open field test were evident in the block animals. The wooden block was found effectively to prevent the accumulation of dental plaque and development of hypertrophia gingiva. However, both the block and the straw markedly increased the incidence of hyperaemia in the mucous membrane of the stomach and intestine. This may explain the lower weight development in these groups than in the controls. Significant differences were not found between the experimental groups in blood screen (haemoglobin, white blood cells, red blood cells, haematocrit) or in the cortisol:creatinine ratio analysed from 24-h urine. The body-weight-related adrenal weight, however, tended to be lowest in the block animals. Furthermore, the presence of a wooden block in a cage significantly reduced the amount of oral stereotypies during the latter part of the growing season. Significant differences did not exist in economically important fur characteristics (quality, mass, cover). It is suggested that further studies on alternative chewing objects should be conducted before introducing such environmental enrichments into farming practice. Electronic Publication     

Photoperiod and fur lengths in the arctic fox (Alopex lagopus L.)

Pelage is seasonally dimorphic in the Arctic fox. During the winter, fur lengths for this species are nearly double similar values taken during the summer season. Considerable site-specific differences in fur length are noted. In general, body sites which are exposed to the environment when an Arctic fox lies in a curled position show greater fur lengths in all seasons and greater seasonal variations than body sites that are more protected during rest. Well-furred sites may tend to conserve heat during periods of inactivity, and scantily furred sites may tend to dissipate heat during periods of exercise. The growth of winter fur may compensate for the severe cold of the arctic winter. Changes in fur lengths indicate a definite pattern in spite of individual variations. During the fall months, fur lengths seem to lag behind an increasing body-to-ambient temperature gradient. Both body-to-ambient temperature gradients and fur lengths peak during December through February. From March through June, gradual environmental warming is accompanied by a decrease in average fur lengths. Thus, there appears to be a remarkable parallel between the body-to-ambient temperature gradient and the fur lengths. The growth of fur in the Arctic fox parallels annual changes in ambient temperature and photoperiod.Presented at the Eighth International Congres of Biometerorology, 9–14 September 1979, Shefayim, Israel.