| 1. |
- Angerbjörn, Anders, et al.
(författare)
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Dietary Variation in Arctic Foxes (Alopex-Lagopus) - an Analysis of Stable Carbon Isotopes
- 1994
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Ingår i: Oecologia. ; 99:3-4, s. 226-232
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Tidskriftsartikel (refereegranskat)abstract
- 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 seat 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 delta(13)C values of -21.4 (Ice land) and -20.4 parts per thousand (Sweden), showing typical terrestrial values. Coastal foxes from Greenland had typical marine Values of -14.9 parts per thousand, whereas coastal foxes from Iceland had intermediate values of -17.7 parts per thousand. 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 seat 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.
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| 2. |
- Geffen, E., et al.
(författare)
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Kin encounter rate and inbreeding avoidance in canids
- 2011
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Ingår i: Molecular Ecology. - 0962-1083 .- 1365-294X. ; 20:24, s. 5348-5358
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Tidskriftsartikel (refereegranskat)abstract
- 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
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| 3. |
- Hersteinsson, P., et al.
(författare)
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The Arctic Fox in Fennoscandia and Iceland - Management Problems
- 1989
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Ingår i: Biological Conservation. - : Elsevier BV. - 0006-3207 .- 1873-2917. ; 49:1, s. 67-81
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Tidskriftsartikel (refereegranskat)abstract
- The arctic for Alopex lagopus was an important fur animal in Fennoscandia until the 1920s when numbers crashed, and in spite of total protection for over half a century has not recovered and is now regarded as vulnerable. In Iceland, on the other hand, the species is well established and can withstand heavy exploitation by man, being regarded as vermin and hunted at all seasons. In this paper we review the latest available information on the status of the arctic fox in the Nordic countries, both with regard to minimum sizes and fluctuations in population, and various factors which have been suggested as the cause of the non-recovery of the population in Fennoscandia. These include fewer available large mammal carcasses due to the near-disappearance of the wolf, increased competition with the red fox, increased predation by red foxes on arctic foxes, etc. The views that arctic foxes are an important predator on sheep in Iceland at present, and that foxhunting alone in its present form is capable of significantly reducing the population there, are challenged. At present there is insufficient information to make sound management programmes for the arctic fox populations in Fennoscandia and Iceland. Suggestions are made concerning those factors which need to be explored so that workable management programmes can be put into effect in the two regions.
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| 4. |
- Unnsteinsdottir, E. R., et al.
(författare)
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The fall and rise of the Icelandic Arctic fox (Vulpes lagopus) : a 50-year demographic study on a non-cyclic Arctic fox population
- 2016
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Ingår i: Oecologia. - : Springer Science and Business Media LLC. - 0029-8549 .- 1432-1939. ; 181:4, s. 1129-1138
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Tidskriftsartikel (refereegranskat)abstract
- In territorial species, observed density dependence is often manifest in lowered reproductive output at high population density where individuals have fewer resources or are forced to inhabit low-quality territories. The Arctic fox (Vulpes lagopus) in Iceland is territorial throughout the year and feeds mostly on birds, since lemmings are absent from the country. Thus, the population does not exhibit short-term population cycles that are evident in most of the species' geographical range. The population has, however, gone through a major long-term fluctuation in population size. Because of the stability in hunting effort and reliable hunting records since 1958, the total number of adult foxes killed annually can be used as an index of population size (N (t) ). An index of carrying capacity (K) from population growth data for five separate time blocks during 1958-2007 revealed considerable variation in K and allowed a novel definition of population density in terms of K, or N (t) /K. Correlation analysis suggested that the reproductive rate was largely determined by the proportion of territorial foxes in the population. Variation in litter size and cub mortality was, on the other hand, related to climatic variation. Thus, Arctic foxes in Iceland engage in typical contest competition but can adapt their territory sizes in response to both temporal and spatial variation in carrying capacity, resulting in surprisingly little variation in litter size.
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