Attracting Arctic Foxes to Relocate a Gull Colony at Keflavik International Airport (Poster)

The Lesser Black-backed Gull (Larus fuscus) colony at Keflavik International Airport has grown from around 1,000 pairs in 1975 to over 20,000 pairs in the early 1990s and to around 30,000 pairs in 2000. The colony is considered a serious hazard to both military and civil air traffic. The population of arctic foxes (Alopex lagopus), the only predator in Iceland capable of preying on these gulls, was very small in this area from the late 1950s until the mid-1980s. A decade ago we noted that the location of the colony had shifted away from an arctic fox breeding den near the airport. As there were no natural arctic fox breeding dens at the location of the gull colony and as the geography was not suitable for such dens, we constructed an artificial den there in autumn 2000 to attract arctic foxes to breed there. The design of the den was based on that of a natural arctic fox den excavated elsewhere. Between January and April 2001, bird carcasses were placed at the artificial den on a regular basis to attract the foxes’ attention to the den. Tracks in snow showed that foxes visited the den and removed the gull carcasses. Two vixens, one pregnant and the other lactating, were killed in the vicinity of the den in May and June 2001, respectively, and it was not used as a breeding den that year. We propose that arctic foxes should be totally protected in the area in order to test (a) whether wild arctic foxes are prepared to use an artificial den for rearing their pups, and (b) whether the occupation of a strategically placed den will result in a relocation of the gull colony to an area where aviation hazards are not a problem

Kin encounter rate and inbreeding avoidance in canids

Mating with close kin can lead to inbreeding depression through the expression of recessive deleterious alleles and loss of heterozygosity. Mate selection may be affected by kin encounter rate, and inbreeding avoidance may not be uniform but associated with age and social system. Specifically, selection for kin recognition and inbreeding avoidance may be more developed in species that live in family groups or breed cooperatively. To test this hypothesis, we compared kin encounter rate and the proportion of related breeding pairs in noninbred and highly inbred canid populations. The chance of randomly encountering a full sib ranged between 1–8% and 20–22% in noninbred and inbred canid populations, respectively. We show that regardless of encounter rate, outside natal groups mates were selected independent of relatedness. Within natal groups, there was a significant avoidance of mating with a relative. Lack of discrimination against mating with close relatives outside packs suggests that the rate of inbreeding in canids is related to the proximity of close relatives, which could explain the high degree of inbreeding depression observed in some populations. The idea that kin encounter rate and social organization can explain the lack of inbreeding avoidance in some species is intriguing and may have implications for the management of populations at risk

The Influence of Coastal Access on Isotope Variation in Icelandic Arctic Foxes

To quantify the ecological effects of predator populations, it is important to evaluate how population-level specializations are dictated by intra- versus inter-individual dietary variation. Coastal habitats contain prey from the terrestrial biome, the marine biome and prey confined to the coastal region. Such habitats have therefore been suggested to better support predator populations compared to habitats without coastal access. We used stable isotope data on a small generalist predator, the arctic fox, to infer dietary strategies between adult and juvenile individuals with and without coastal access on Iceland. Our results suggest that foxes in coastal habitats exhibited a broader isotope niche breadth compared to foxes in inland habitats. This broader niche was related to a greater diversity of individual strategies rather than to a uniform increase in individual niche breadth or by individuals retaining their specialization but increasing their niche differentiation. Juveniles in coastal habitats exhibited a narrower isotope niche breadth compared to both adults and juveniles in inland habitats, and juveniles in inland habitats inhabited a lower proportion of their total isotope niche compared to adults and juveniles from coastal habitats. Juveniles in both habitats exhibited lower intra-individual variation compared to adults. Based on these results, we suggest that foxes in both habitats were highly selective with respect to the resources they used to feed offspring, but that foxes in coastal habitats preferentially utilized marine resources for this purpose. We stress that coastal habitats should be regarded as high priority areas for conservation of generalist predators as they appear to offer a wide variety of dietary options that allow for greater flexibility in dietary strategies

The behavioural ecology of the Arctic fox (Alopex lagopus) in Iceland

During the last 20 years studies of various mammals and birds have shown that social organization is highly variable between and within species, and that such variation can frequently be explained on the basis of variation in food habits and food dispersion. This study is an attempt to discover the major ecological pressures affecting social organization and reproductive fitness of Arctic foxes in Iceland. Foxes were both studied at an individual level, by monitoring movements of radio-tagged foxes and observation of fox behaviour in demarcated study areas, and at the population level, by analysis of available foxhunting records, as well as material and information provided by foxhunters. The most common form of social organization was found to be a breeding pair, while social groups of 3-4 individuals also occur, particularly in coastal habitat, which is more productive and spatially more heterogenous with respect to food dispersion, than inland habitat. The Arctic foxes were found to occupy well defined, but fairly flexible group territories, whose borders were advertised by olfactory, auditory and visual signals. In one coastal region, three such territories ranged in size from 8.6 km2 to 18.5 km2, while there was an indication that territories were larger in inland habitats. In coastal habitats, foxes feed mainly on oceanic prey and do not show cycles in abundance. In inland habitat, foxes show a functional response to the 10 year population cycle of ptarmigan (Lagopus mutus), their main prey in winter. Litter sizes remain stable, however, due to little interannual variation in the foxes' summer diet, which consists mostly of migrant birds. Mean litter size at birth is 5-3 ± 1.7 S.D. and mortality from factors other than foxhunting is about 15% up to the age of weaning. Annual mortality in adults is about 50%, mostly due to foxhunting. Most vixens breed already as yearlings, while dog-foxes are more likely to show delayed breeding. In inland habitats there is balanced polymorphism with regard to colour morph, but in coastal habitats blue foxes have an overall selective advantage. Inland foxes are smaller than coastal foxes. Both size and colour affect reproductive fitness.</p

Average δ¹³C and δ¹⁵N values of potential prey available in coastal and inland habitats in Iceland.

1<p>) Data from interior Alaska <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0032071#pone.0032071-Dalerum3" target="_blank">[56]</a>.</p><p>The prey table is not comprehensive and data are not intended for quantitative analyses, but rather to exemplify the wider isotope niche width that is available in coastal habitats.</p

Isotope niche breadth of adult and juvenile foxes from coastal (open symbols) and inland (closed symbols) habitats on Iceland.

<p>Isotope niche breadth was estimated as the Euclidian distances to group centroids in a 2 dimensional isotope space formed by δ¹³C and δ¹³N. Figure presents mean ± 1 SE.</p

Results from linear mixed models on the effects of habitat (coastal or inland) and age of animal (adult or juvenile) on three attributes of individual variation in δ¹³C and δ¹⁵N.

<p>Within individual isotope niche breadth was estimated as the Euclidean distance between collagen and muscle within individuals, between individual variation in individual isotope niche breadth was calculated as the Euclidean distance of each individual difference between muscle and collagen to group centroids in a 2 dimensional isotope space, and an individual specialization index that relates intra individual variation to the total isotope niche breadth of each sample group, calculated as the ratio of the average Euclidean distances of muscle and collagen samples to within individual centroids and the average Euclidean distances to group centroids. Groups were in all cases defined as age classes within each habitat.</p

Results from linear mixed models on the effects of habitat (coastal or inland), age of animal (adult or juvenile) and tissue (fur, muscle and collagen) on δ¹³C and δ¹⁵N in Icelandic arctic foxes.

<p>Results from linear mixed models on the effects of habitat (coastal or inland), age of animal (adult or juvenile) and tissue (fur, muscle and collagen) on δ¹³C and δ¹⁵N in Icelandic arctic foxes.</p

Biplots of δ¹³C and δ¹³N values of fur (A, B), muscle (C, D) and collagen (E, F) samples from adult and juvenile arctic foxes from coastal (open symbols) and inland (closed symbols) habitats on Iceland.

<p>Biplots of δ¹³C and δ¹³N values of fur (A, B), muscle (C, D) and collagen (E, F) samples from adult and juvenile arctic foxes from coastal (open symbols) and inland (closed symbols) habitats on Iceland.</p