| 1. |
- Ehrich, Dorothee, et al.
(author)
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Documenting lemming population change in the Arctic : Can we detect trends?
- 2020
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In: Ambio. - : Springer Science and Business Media LLC. - 0044-7447 .- 1654-7209. ; 49:3, s. 786-800
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Journal article (peer-reviewed)abstract
- Lemmings are a key component of tundra food webs and changes in their dynamics can affect the whole ecosystem. We present a comprehensive overview of lemming monitoring and research activities, and assess recent trends in lemming abundance across the circumpolar Arctic. Since 2000, lemmings have been monitored at 49 sites of which 38 are still active. The sites were not evenly distributed with notably Russia and high Arctic Canada underrepresented. Abundance was monitored at all sites, but methods and levels of precision varied greatly. Other important attributes such as health, genetic diversity and potential drivers of population change, were often not monitored. There was no evidence that lemming populations were decreasing in general, although a negative trend was detected for low arctic populations sympatric with voles. To keep the pace of arctic change, we recommend maintaining long-term programmes while harmonizing methods, improving spatial coverage and integrating an ecosystem perspective.
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| 2. |
- Elmhagen, Bodil, et al.
(author)
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Homage to Hersteinsson and Macdonald : climate warming and resource subsidies cause red fox range expansion and Arctic fox decline
- 2017
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In: Polar Research. - : Norwegian Polar Institute. - 0800-0395 .- 1751-8369. ; 36:suppl. 1
-
Research review (peer-reviewed)abstract
- Climate change can have a marked effect on the distribution and abundance of some species, as well as their interspecific interactions. In 1992, before ecological effects of anthropogenic climate change had developed into a topical research field, Hersteinsson and Macdonald published a seminal paper hypothesizing that the northern distribution limit of the red fox (Vulpes vulpes) is determined by food availability and ultimately climate, while the southern distribution limit of the Arctic fox (Vulpes lagopus) is determined by interspecific competition with the larger red fox. This hypothesis has inspired extensive research in several parts of the circumpolar distribution range of the Arctic fox. Over the past 25 years, it was shown that red foxes can exclude Arctic foxes from dens, space and food resources, and that red foxes kill and sometimes consume Arctic foxes. When the red fox increases to ecologically effective densities, it can cause Arctic fox decline, extirpation and range contraction, while conservation actions involving red fox culling can lead to Arctic fox recovery. Red fox advance in productive tundra, concurrent with Arctic fox retreat from this habitat, support the original hypothesis that climate warming will alter the geographical ranges of the species. However, recent studies show that anthropogenic subsidies also drive red fox advance, allowing red fox establishment north of its climate-imposed distribution limit. We conclude that synergies between anthropogenic subsidies and climate warming will speed up Arctic ecosystem change, allowing mobile species to establish and thrive in human-provided refugia, with potential spill-over effects in surrounding ecosystems.
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| 3. |
- Aguirre, A. A., et al.
(author)
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Health evaluation of arctic fox (Alopex lagopus) cubs in Sweden
- 2000
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In: Journal of zoo and wildlife medicine. - 1042-7260 .- 1937-2825. ; 31:1, s. 36-40
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Journal article (peer-reviewed)abstract
- Hematologic. serum biochemistry, and serum cortisol reference ranges were established and tonsil/rectal bacterial and fecal parasite examinations were performed on 21 wild arctic fox (Alopex lagopus) cubs during July 1996. Several of the hematologic and serum biochemistry values fell within normal ranges for other wild canids or domestic dogs of the same age class. Serum alanine transaminase and creatine phosphokinase values were significantly higher in the youngest cubs. Proteus vulgaris and Escherichia coli were isolated from both tonsilar and rectal swabs of several cubs in all dens. The most common gastrointestinal parasite ova were Toxascaris leonina (59%), Isospora spp. (52%), Uncinaria stenocephala (33%), and Capillaria spp. (26%). Prevalence of T. leonina differed significantly between dens and between age groups. Hematologic and serum biochemistry values and degree of parasitism may be indicators of health, stress, and nutritional status of arctic foxes.
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| 4. |
- Krebs, C. J., et al.
(author)
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Terrestrial trophic dynamics in the Canadian Arctic
- 2003
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In: Canadian Journal of Zoology-Revue Canadienne De Zoologie. ; 81, s. 827-843
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Journal article (peer-reviewed)abstract
- The Swedish Tundra Northwest Expedition of 1999 visited 17 sites throughout the Canadian Arctic. At 12 sites that were intensively sampled we estimated the standing crop of plants and the densities of herbivores and predators with an array of trapping, visual surveys, and faecal-pellet transects. We developed a trophic-balance model using ECOPATH to integrate these observations and determine the fate of primary and secondary production in these tundra ecosystems, which spanned an 8-fold range of standing crop of plants. We estimated that about 13% of net primary production was consumed by herbivores, while over 70% of small-herbivore production was estimated to flow to predators. Only 9% of large-herbivore production was consumed by predators. Organization of Canadian Arctic ecosystems appears to be more top-down than bottom-up. Net primary production does not seem to be herbivore-limited at any site. This is the first attempt to integrate trophic dynamics over the entire Canadian Arctic.
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| 5. |
- Elmhagen, Bodil, et al.
(author)
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Interacting effects of change in climate, human population, land use, and water use on biodiversity and ecosystem services
- 2015
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In: Ecology and Society. - 1708-3087. ; 20:1
-
Journal article (peer-reviewed)abstract
- Human population growth and resource use, mediated by changes in climate, land use, and water use, increasingly impact biodiversity and ecosystem services provision. However, impacts of these drivers on biodiversity and ecosystem services are rarely analyzed simultaneously and remain largely unknown. An emerging question is how science can improve the understanding of change in biodiversity and ecosystem service delivery and of potential feedback mechanisms of adaptive governance. We analyzed past and future change in drivers in south-central Sweden. We used the analysis to identify main research challenges and outline important research tasks. Since the 19th century, our study area has experienced substantial and interlinked changes; a 1.6 degrees C temperature increase, rapid population growth, urbanization, and massive changes in land use and water use. Considerable future changes are also projected until the mid-21st century. However, little is known about the impacts on biodiversity and ecosystem services so far, and this in turn hampers future projections of such effects. Therefore, we urge scientists to explore interdisciplinary approaches designed to investigate change in multiple drivers, underlying mechanisms, and interactions over time, including assessment and analysis of matching-scale data from several disciplines. Such a perspective is needed for science to contribute to adaptive governance by constantly improving the understanding of linked change complexities and their impacts.
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| 6. |
- Henden, J-A, et al.
(author)
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Phase-dependent effect of conservation efforts in cyclically fluctuating populations of Arctic fox (Vulpes lagopus).
- 2009
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In: Biological Conservation. - : Elsevier BV. - 0006-3207 .- 1873-2917. ; 142, s. 2586-2592
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Journal article (peer-reviewed)abstract
- Predator populations with demographic cycles driven by multi-annual cycles of their key prey resourcecan be expected to be ‘‘cyclic phase sensitive” to management actions. We explored this by means ofmodelling in the case of the highly endangered Fennoscandian arctic fox population which is driven by4-year population cycles in small rodent prey. By using a model in which the management actionimproved arctic fox vital rate through increased resource availability, we show that arctic fox populationgrowth was most improved when management action was applied in the increase and decrease phase ofthe cycle. Except in the low phase of the cycle, the growth rate was more affected when the managementaction worked through improved reproduction than improved survival. There was a synergistic effect tobe gained by performing management action during multiple phases during a demographic cycle. Thuswe recommend that arctic fox conservation programs ought to be continuous in time, but with the highestintensities of management action in the phases of the cycle in which the target population is mostprone to respond.
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| 7. |
- Krebs, C. J., et al.
(author)
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Synchrony in lemming and vole populations in the Canadian Arctic
- 2002
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In: Canadian Journal of Zoology-Revue Canadienne De Zoologie. ; 80:8, s. 1323-1333
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Journal article (peer-reviewed)abstract
- Population fluctuations may occur in synchrony among several rodent species at a given site, and they may occur in synchrony over large geographical areas. We summarize information on synchrony in lemmings and voles from the Canadian Arctic for the past 20 years. The most detailed available information is from the central Canadian Arctic, where snap-trap samples have been taken annually at several sites for periods of up to 15 years. Geographical synchrony in the same species among different sites was strong, especially for the central and eastern Canadian Arctic. Synchrony among different species at a given site was also generally high. When one species is at high density, densities of all species at that site tend to be high. These results do not easily fit the mobile-predator hypothesis proposed to explain regional synchrony, and are more consistent with the weather hypothesis, which we suggest both entrains synchrony among sites and enforces synchrony among species within a site. We tentatively support the weather hypothesis for geographical synchrony in lemmings, and recommend the establishment of a circumpolar program to monitor lemming cycles and predator movements that would advance our understanding of these large-scale patterns of cyclic synchrony.
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| 8. |
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| 9. |
- Aguirre, A. Alonso, et al.
(author)
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Field anesthesia of wild arctic fox (Alopex lagopus) cubs in the Swedish lapland using medetomidine-ketamine-atipamezole
- 2000
-
In: Journal of zoo and wildlife medicine. - 1042-7260 .- 1937-2825. ; 31:2, s. 244-246
-
Journal article (peer-reviewed)abstract
- A safe and effective anesthetic regime for use in arctic fox (Alopex lagopus) cubs was developed. During July 1996, six free-ranging 6-8-wk-old cubs were captured near their den in Vindelfjallen Nature Reserve, Sweden. Medetomidine and ketamine HCl, followed by atipamezole, were selected for the anesthetic trial because of the well-documented safety and efficacy of this drug combination in a broad range of species. The dosage regimen used was 50 mu g/kg medetomidine combined with 2.5 mg/kg ketamine followed by reversal with 250 mu g/kg atipamezole. induction was rapid, with a mean induction time of 1 min and 32 sec (range: 58-150 sec). The cubs were anesthetized for a mean time of 18 +/- 5 min (range: 13-25 min). Serially recorded heart rate, respiratory rate, temperature, and pulse oximetry were stable throughout the anesthetic period for all cubs. Anesthetic depth was suitable for safe handling and minor clinical procedures, including venipuncture. Following atipamezole, all cubs were standing within 12 +/- 7 min (range: 5-24 min) and fully recovered at 27 +/- 5 min (range: 19-36 min). This information will be useful for future captive breeding and management programs involving the endangered arctic fox.
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| 10. |
- Angerbjörn, Anders, et al.
(author)
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Carnivore conservation in practice : replicatedmanagement actions on a large spatial scale
- 2013
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In: Journal of Applied Ecology. - : Wiley. - 0021-8901 .- 1365-2664. ; 50:1, s. 59-67
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Journal article (peer-reviewed)abstract
- More than a quarter of the world’s carnivores are threatened, often due to multiple andcomplex causes. Considerable research efforts are devoted to resolving the mechanisms behindthese threats in order to provide a basis for relevant conservation actions. However, evenwhen the underlying mechanisms are known, specific actions aimed at direct support for carnivoresare difficult to implement and evaluate at efficient spatial and temporal scales.2. We report on a 30-year inventory of the critically endangered Fennoscandian arctic foxVulpes lagopus L., including yearly surveys of 600 fox dens covering 21 000 km2. These surveysshowed that the population was close to extinction in 2000, with 40–60 adult animalsleft. However, the population subsequently showed a fourfold increase in size.3. During this time period, conservation actions through supplementary feeding and predatorremoval were implemented in several regions across Scandinavia, encompassing 79% of thearea. To evaluate these actions, we examined the effect of supplemental winter feeding andred fox control applied at different intensities in 10 regions. A path analysis indicated that47% of the explained variation in population productivity could be attributed to lemmingabundance, whereas winter feeding had a 29% effect and red fox control a 20% effect.4. This confirms that arctic foxes are highly dependent on lemming population fluctuationsbut also shows that red foxes severely impact the viability of arctic foxes. This study also highlightsthe importance of implementing conservation actions on extensive spatial and temporalscales, with geographically dispersed actions to scientifically evaluate the effects. We note thatpopulation recovery was only seen in regions with a high intensity of management actions.5. Synthesis and applications. The present study demonstrates that carnivore populationdeclines may be reversed through extensive actions that target specific threats. Fennoscandianarctic fox is still endangered, due to low population connectivity and expected climate impactson the distribution and dynamics of lemmings and red foxes. Climate warming is expected tocontribute to both more irregular lemming dynamics and red fox appearance in tundra areas;however, the effects of climate change can be mitigated through intensive managementactions such as supplemental feeding and red fox control.
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| 11. |
- Angerbjörn, Anders, et al.
(author)
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Dynamics of the Arctic Fox Population in Sweden
- 1995
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In: Annales Zoologici Fennici. ; 32:1, s. 55-68
-
Journal article (peer-reviewed)abstract
- Arctic fox populations fluctuate widely with the abundance of prey, i.e. lemmings and voles (Arvicolinae). We have investigated the patterns and mechanisms of these fluctuations in arctic fox numbers through den inventories during 20 years (1974-1993) in Sweden. Time series analyses confirmed a four-year cyclicity in both arctic fox numbers and litter size. However, the different geographical regions were not in synchrony. The fox population in the southern parts of the distribution range has shown regular peaks during the whole period, whereas those in the northern and middle parts of Sweden have declined since 1982. In the northernmost county, also litter sizes have decreased. These differences coincided with an absence of vole and lemming peaks in the north. Experimental feeding confirmed that food availability had a direct impact on breeding success and litter size, thereby limiting the population. We conclude that the total number of arctic foxes in Sweden in 1994 is as low as 40-80 animals.
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| 12. |
- Angerbjörn, Anders, et al.
(author)
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Factors Influencing Winter Food Choice by Mountain Hares (Lepus-Timidus L) on Swedish Coastal Islands
- 1987
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In: Canadian Journal of Zoology. - : Canadian Science Publishing. - 0008-4301 .- 1480-3283. ; 65:9, s. 2163-2167
-
Journal article (peer-reviewed)abstract
- In mainland areas, mountain hares seem unable to survive on a single browse species. However, mountain hares on islands off the west coast of Sweden rely almost entirely on a plain heather diet during winter. Herein, we give as a possible explanation for this phenomenon that the high concentration of sodium in the heather in the coastal areas can buffer the high sodium excretion otherwise observed in hares feeding on heather under experimental conditions. Furthermore, hares selected heather with the highest nitrogen and phosphorus contents. We argue that the pattern of food choice exhibited by the hares in the coastal area is to be expected in homogenous habitats where hares rely on one dominant food species. In heterogenous habitats, the possibility of food selection on a nutritional level is to a considerable extent overridden by effects of digestibility and concentration of secondary compounds in the different food plants available.
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| 13. |
- Berteaux, Dominique, et al.
(author)
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Arctic and red foxes
- 2011
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In: Arctic WOLVES. - Quebec City, Quebec, Canada : Centre d’études nordiques, Université Laval. ; , s. 76-87
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Book chapter (other academic/artistic)
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| 14. |
- Berteaux, Dominique, et al.
(author)
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Harmonizing circumpolar monitoring of Arctic fox : benefits, opportunities, challenges and recommendations
- 2017
-
In: Polar Research. - : Norwegian Polar Institute. - 0800-0395 .- 1751-8369. ; 36:suppl. 1
-
Journal article (peer-reviewed)abstract
- The biodiversity working group of the Arctic Council has developed pan-Arctic biodiversity monitoring plans to improve our ability to detect, understand and report on long-term change in Arctic biodiversity. The Arctic fox (Vulpes lagopus) was identified as a target of future monitoring because of its circumpolar distribution, ecological importance and reliance on Arctic ecosystems. We provide the first exhaustive survey of contemporary Arctic fox monitoring programmes, describing 34 projects located in eight countries. Monitored populations covered equally the four climate zones of the species’ distribution, and there were large differences between populations in long-term trends, multi-annual fluctuations, diet composition, degree of competition with red fox and human interferences. Den density, number of active dens, number of breeding dens and litter size were assessed in almost all populations, while projects varied greatly with respect to monitoring of other variables indicative of population status, ecosystem state or ecosystem function. We review the benefits, opportunities and challenges to increased integration of monitoring projects. We argue that better harmonizing protocols of data collection and data management would allow new questions to be addressed while adding tremendous value to individual projects. However, despite many opportunities, challenges remain. We offer six recommendations that represent decisive progress toward a better integration of Arctic fox monitoring projects. Further, our work serves as a template that can be used to integrate monitoring efforts of other species, thereby providing a key step for future assessments of global biodiversity.
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| 15. |
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| 16. |
- Bruun, Hans Henrik, et al.
(author)
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Effects of altitude and topography on species richness of vascular plants, bryophytes and lichens in alpine communities
- 2006
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In: Journal of Vegetation Science. - 1100-9233 .- 1654-1103. ; 17:1, s. 37-46
-
Journal article (peer-reviewed)abstract
- Question: What is the relationship between species richness of vascular plants, bryophytes and macrolichens, and two important gradients in the alpine environment, altitude and local topography? Location: Northernmost Fennoscandia, 250-152 m a.s.l. corresponding to the range between timberline and mountain top. Methods: The vegetation was sampled in six mountain areas. For each 25 vertical metres, the local topographic gradient from wind-blown ridge to snowbed was sampled in quadrats of 0.8 m x 0.8 m. Patterns in species richness were explored using Poisson regression (Generalized Linear Models). Functional groups of species, i.e. evergreen and deciduous dwarf-shrubs, forbs, graminoids, mosses, hepatics and lichens were investigated separately. Results: Functional groups showed markedly different patterns with respect to both altitude and topography. Species richness of all vascular plants showed a unimodal relationship with altitude. The same was true for graminoids, forbs and lichens analysed separately, but forb richness peaked at Much higher altitudes than total richness. The richness of dwarf-shrubs decreased monotonically with altitude, whereas richness of mosses and liverworts showed an increasing trend. Significant interactions between altitude and local topography were present for several groups. The unimodal pattern for total plant species richness was interpreted in terms of local productivity, physical disturbance, trophic interactions, and in terms of species pool effects. Conclusions: Patterns in local species richness result from the action of two opposing forces: declining species pool and decreasing intensity of competition with altitude.
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| 17. |
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| 18. |
- Dalen, L, et al.
(author)
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Identifying species from pieces of faeces
- 2004
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In: Conservation Genetics. - DORDRECHT : KLUWER ACADEMIC PUBL. - 1566-0621 .- 1572-9737. ; 5:1, s. 109-111
-
Journal article (peer-reviewed)
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| 19. |
- Dalén, Love, et al.
(author)
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Population structure in a critically endangered arctic fox population : does genetics matter?
- 2006
-
In: Molecular Ecology. - 0962-1083 .- 1365-294X. ; 15:10, s. 2809-2819
-
Journal article (peer-reviewed)abstract
- The arctic fox (Alopex lagopus) in Scandinavia is classified as critically endangered after having gone through a severe decline in population size in the beginning of the 20th century, from which it has failed to recover despite more than 65 years of protection. Arctic foxes have a high dispersal rate and often disperse over long distances, suggesting that there was probably little population differentiation within Scandinavia prior to the bottleneck. It is, however, possible that the recent decline in population size has led to a decrease in dispersal and an increase in population fragmentation. To examine this, we used 10 microsatellite loci to analyse genetic variation in 150 arctic foxes from Scandinavia and Russia. The results showed that the arctic fox in Scandinavia presently is subdivided into four populations, and that the Kola Peninsula and northwest Russia together form a large fifth population. Current dispersal between the populations seemed to be very low, but genetic variation within them was relatively high. This and the relative F-ST values among the populations are consistent with a model of recent fragmentation within Scandinavia. Since the amount of genetic variation is high within the populations, but the populations are small and isolated, demographic stochasticity seems to pose a higher threat to the populations' persistence than inbreeding depression and low genetic variation.
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| 20. |
- Dalerum, Fredrik, et al.
(author)
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Exploring the diet of arctic wolves (Canis lupus arctos) at their northern range limit
- 2018
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In: Canadian Journal of Zoology. - : Canadian Science Publishing. - 0008-4301 .- 1480-3283. ; 96:3, s. 277-281
-
Journal article (peer-reviewed)abstract
- The grey wolf (Canis lupus Linnaeus, 1758) is one of the most widespread large carnivores on Earth, and occurs throughout the Arctic. Although wolf diet is well studied, we have scant information from high Arctic areas. Global warming is expected to increase the importance of predation for ecosystem regulation in Arctic environments. To improve our ability to manage Arctic ecosystems under environmental change, we therefore need knowledge about Arctic predator diets. Prey remains in 54 wolf scats collected at three sites in the high Arctic region surrounding the Hall Basin (Judge Daly Promontory, Ellesmere Island, Canada, and Washington Land and Hall Land, both in northwestern Greenland) pointed to a dietary importance of arctic hare (Lepus arcticus Ross, 1819; 55% frequency of occurrence) and muskoxen (Ovibos moschatus (Zimmermann, 1780); 39% frequency of occurrence), although we observed diet variation among the sites. A literature compilation suggested that arctic wolves (Canis lupus arctos Pocock, 1935) preferentially feed on caribou (Rangifer tarandus (Linnaeus, 1758)) and muskoxen, but can sustain themselves on arctic hares and Greenland collared lemmings (Dicrostonyx groenlandicus (Traill, 1823)) in areas with limited or no ungulate populations. We suggest that climate change may alter the dynamics among wolves, arctic hare, muskoxen, and caribou, and we encourage further studies evaluating how climate change influences predator-prey interactions in high Arctic environments.
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| 21. |
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| 22. |
- Geffen, Eli, et al.
(author)
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Sea ice occurrence predicts genetic isolation in the Arctic fox
- 2007
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In: Molecular Ecology. - 0962-1083 .- 1365-294X. ; 16:20, s. 4241-4255
-
Journal article (peer-reviewed)abstract
- Unlike Oceanic islands, the islands of the Arctic Sea are not completely isolated from migration by terrestrial vertebrates. The pack ice connects many Arctic Sea islands to the mainland during winter months. The Arctic fox (Alopex lagopus), which has a circumpolar distribution, populates numerous islands in the Arctic Sea. In this study, we used genetic data from 20 different populations, spanning the entire distribution of the Arctic fox, to identify barriers to dispersal. Specifically, we considered geographical distance, occurrence of sea ice, winter temperature, ecotype, and the presence of red fox and polar bear as nonexclusive factors that influence the dispersal behaviour of individuals. Using distance-based redundancy analysis and the BIOENV procedure, we showed that occurrence of sea ice is the key predictor and explained 40-60% of the genetic distance among populations. In addition, our analysis identified the Commander and Pribilof Islands Arctic populations as genetically unique suggesting they deserve special attention from a conservation perspective.
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| 23. |
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| 24. |
- Hersteinsson, P., et al.
(author)
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The Arctic Fox in Fennoscandia and Iceland - Management Problems
- 1989
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In: Biological Conservation. - : Elsevier BV. - 0006-3207 .- 1873-2917. ; 49:1, s. 67-81
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Journal article (peer-reviewed)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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| 25. |
- Kaikusalo, A., et al.
(author)
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The Arctic Fox Population in Finnish Lapland During 30 Years, 1964-93
- 1995
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In: Annales Zoologici Fennici. - 0003-455X .- 1797-2450. ; 32:1, s. 69-77
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Journal article (peer-reviewed)abstract
- We have monitored the number of arctic foxes and microtine rodents in northern Finland for 30 years. Arctic fox densities were estimated by inventories at den sites, and microtine abundance by snap trapping. Time series analyses showed that the arctic fox population fluctuated widely but always close together with the microtines in a five year cycle. However, there was no time lag in the numerical response of foxes on microtines. The strong dependence on microtines was confirmed by analyses of faecal droppings and food remains at dens. In summer time microtines consisted in average of 45% of the diet and reindeer 30%, but during winters reindeer was the most important food source with 45% compared to 15% for microtines. There was a surprising positive correlation between number of voles and reindeer carcasses, suggesting competition or alternatively an external correlation from e.g. weather. Mean litter size of the arctic fox was also highly dependent on microtine abundance but decreased during the study period despite that food resources had not changed. Further, when microtines had high densities during two consecutive years, arctic foxes only responded to the first year. A feeding experiment resulted in an increase in number of red foxes but had no or little effect on arctic foxes. So, it is difficult to single out one explanation to the decline and second year effect. Food was probably not involved and we do not know if diseases and parasites have been involved. However, both competition and predation, primarily from the red fox, may be responsible together with climatic or weather changes.
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| 26. |
- Kullberg, C., et al.
(author)
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Social-Behavior and Cooperative Breeding in Arctic Foxes, Alopex-Lagopus (L), in a Seminatural Environment
- 1992
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In: Ethology. ; 90:4, s. 321-335
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Journal article (peer-reviewed)abstract
- Most canid species show cooperative breeding at least occasionally, The helper-at-the-den system, when extra adults serve as helpers by feeding and guarding the cubs of an alpha pair, has been observed but not studied in any detail in wild Arctic foxes (Alopex lagopus). During a 3-months study of arctic foxes in two enclosures of 4 ha each, we measured the social behaviour during the reproductive season. Older foxes dominated younger ones and males dominated females of the same age. A litter with one surviving cub was born in one enclosure. The alpha male increased his rate of urine marking and barking and fed the alpha female both before and after the birth of the litter. However, about 10 days after the birth, the alpha female died. The cub was fed by his putative father, his sister and his brother (both one year old). The one year old female increased her rate of territorial defence, measured as urine marking and barking, when the mother died. The subordinate females were probably suppressed from breeding by the high aggression levels and territorial defence of the dominant females in each enclosure. The dominant female in the second enclosure came into beat after the death of the alpha female (her mother) in the first enclosure. These changes in behaviour can probably be explained by sexual inhibition by the alpha female while she was present. The significance of territorial defence and dominance, inbreeding avoidance, sexual suppression and evolution of helping behaviour are discussed.
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| 27. |
- Lagerholm, Vendela K., et al.
(author)
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Run to the hills : gene flow among mountain areas leads to low genetic differentiation in the Norwegian lemming
- 2017
-
In: Biological Journal of the Linnean Society. - : Oxford University Press (OUP). - 0024-4066 .- 1095-8312. ; 121:1, s. 1-14
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Journal article (peer-reviewed)abstract
- The endemic Norwegian lemming (Lemmus lemmus) is an icon for cyclic species, famous since the Middle Ages for its enormous population outbreaks and mass movements. Although the drivers behind this cyclicity have been intensively investigated, virtually nothing is known about the extent to which long-distance dispersal during population peaks actually lead to gene flow among mountain tundra areas. In this article, we use nine microsatellite markers to address this question and analyse range-wide genetic diversity and differentiation between Fennoscandian sub-regions. The results revealed a high genetic variation with a surprisingly weak population structure, comparable to that of much larger mammals. The differentiation was mainly characterized as a genetic cline across the species' entire distribution, and results from spatial autocorrelation analyses suggested that gene flow occurs with sufficiently high frequency to create a genetic patch size of 100 km. Further, we found that for the equivalent distances, the southern sub-regions were genetically more similar to each other than those in the north, which indicates that the prolonged periods of interrupted lemming cyclicity recorded in the northern parts of Fennoscandia have led to increased isolation and population differentiation. In summary, we propose that mass movements during peak years act as pulses of gene flow between mountain tundra areas, and that these help to maintain genetic variation and counteract differentiation over vast geographic distances.
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| 28. |
- Lidén, Kerstin, et al.
(author)
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Dietary change and stable isotopes : a model of growth and dormancy in cave bears
- 1999
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In: Proceedings of the Royal Society of London Series B-Biological Sciences. ; 266:1430, s. 1779-1783
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Journal article (peer-reviewed)abstract
- In order to discuss dietary change over time by the use of stable isotopes, it is necessary to sort out the underlying processes in isotopic variation. Together with the dietary signal other processes have been investigated, namely metabolic processes, collagen turnover and physical growth. However, growth and collagen turnover time have so far been neglected in dietary reconstruction based on stable isotopes. An earlier study suggested that cave bears (Ursus spelaeus) probably gave birth to cubs during dormancy. We provide an estimate of the effect on stable isotopes of growth and metabolism and discuss collagen turnover in a population of cave bears. Based on a quantitative model, we hypothesized that bear cubs lactated their mothers during their first and second winters, but were fed solid food together with lactation during their first summer. This demonstrates the need to include physical growth, metabolism and collagen turnover in dietary reconstruction. Whereas the effects of diet and metabolism are due to fractionation, growth and collagen turnover are dilution processes.
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| 29. |
- Lindenfors, P., et al.
(author)
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The monophyletic origin of delayed implantation in carnivores and its implications
- 2003
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In: Evolution. ; 57:8, s. 1952-1956
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Journal article (peer-reviewed)abstract
- In several carnivores a newly fertilized egg enters diapause instead of being directly implanted into the uterus, a phenomenon called delayed implantation. Several hypotheses have been forwarded to explain the utility of this prolonged gestation period, but all of these depend on several independent origins of the character. Here, we conduct a phylogenetic reconstruction of the evolution of delayed implantation in the Carnivora that reveals one basal origin, with additional transitions all having occurred within the Mustelidae. Hence, previous hypotheses relating to its evolution become untestable. Further analyses revealed that the presence or absence of delayed implantation is unrelated to the timing of mating season and birth season. Instead, mustelids with direct implantation are smaller than those with delayed implantation. We therefore suggest that delayed implantation has been selected against in small species due to the relatively higher fecundity costs of a prolonged gestation period.
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| 30. |
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| 31. |
- Nelson, D. E., et al.
(author)
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Stable isotopes and the metabolism of the European cave bear
- 1998
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In: Oecologia. ; 116:1-2, s. 177-181
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Journal article (peer-reviewed)abstract
- Isotopic analyses of fossil bones of the extinct European cave bear indicate that this animal was a hibernator with the same unusual metabolic processes as some modern bear species. This finding provides useful biological and archaeological information on an extinct species, and the methods themselves may prove generally useful in studies of the metabolisms of modern bears, other hibernators, and perhaps of starving animals.
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| 32. |
- Nyström, Jesper, 1965-
(author)
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Predator-prey interactions of raptors in an arctic environment
- 2004
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Doctoral thesis (other academic/artistic)abstract
- This thesis concerns the predator-prey interactions of three raptor species in a Swedish arctic community: the gyrfalcon (Falco rusticolus), the rough-legged buzzard (Buteo lagopus) and the golden eagle (Aquila chrysaetos). The gyrfalcon behaved like a highly specialised ptarmigan (Lagopus spp.) predator. Gyrfalcon’s functional response to ptarmigan was close to density independent, and ptarmigan remained the dominating prey even in areas with the lowest ptarmigan density. The gyrfalcon did not respond functionally to microtine rodents (i.e. lemmings and voles) and it was clear that the gyrfalcon did not use microtines as an alternative prey category to ptarmigan. As the gyrfalcons did not switch to any alternative prey when ptarmigan was scarce, their reproductive success seemed to be directly dependent on the amount of ptarmigan available in the breeding territories. Of the two ptarmigan species in the study area, rock ptarmigan (L. mutus) dominated gyrfalcon’s diet. Locally, the proportion of rock ptarmigan in gyrfalcons’ diets showed a positive relationship to the expected availability of rock ptarmigan in the breeding territories, indicating a density dependent utilisation. The rough-legged buzzard behaved like a highly specialised microtine rodent predator and Norwegian lemming (Lemmus lemmus) was its preferred microtine species. The buzzards showed a type 2 functional response to lemmings. Surprisingly though, they also had a type 3 functional response to grey-sided voles (Clethrionomus rufocanus). We present an optimal diet model where a central place forager, during good food conditions, benefits from partial prey preference, which renders separate functional responses to each prey category. We discuss how the double functional responses of the buzzard affect the population dynamics of sympatric vole species, on both temporal and spatial scales. The golden eagle behaved like a generalist predator, and it preyed on all major prey categories in the study area: microtines, ptarmigan, mountain hare, (Lepus timidus) and reindeer (Rangifer tarandus). It seemed to respond functionally to microtine rodent fluctuations with an increased consumption of lemmings during a peak year in the microtine rodent cycle. The golden eagle showed a numerical response to its main prey, the ptarmigan. Ptarmigan, microtine rodents and hares seemed to have synchronized population fluctuations in the study area. Such synchronized population fluctuations are believed to be generated by predation. Although the three raptors are the main predators of their community, their predation patterns fail to explain the observed prey population dynamics in the study area.
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| 33. |
- Särnblad, Anna, et al.
(author)
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Population structure and diversity of Indo-Pacific bottlenose dolphins (Tursiops aduncus) in the western Indian Ocean
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Other publication (other academic/artistic)abstract
- Bottlenose dolphin (Tursiops sp.) populations often show small-scale genetic differentiation and have a capacity to adapt both their social strategies and structure to local environmental conditions. Here we investigate population structure and genetic diversity of Indo-Pacific bottlenose dolphins (Tursiops aduncus) in the western Indian Ocean, with special reference to Zanzibar, Tanzania. The Indo-Pacific bottlenose dolphins off Zanzibar were previously hunted and are subject to high levels of bycatch and negative impact from tourism. A recent study has indicated a limited exchange of reproducing females between northern and southern Zanzibar. Mitochondrial DNA sequence (mtDNA 429bp) variation and autosomal genotypes (7 microsatellite loci) was used to assess genetic variation and differentiation among tissue samples from Zanzibar (n=91) Mayotte (n=12) and Oman (n=4). The results showed a much higher amount of differentiation for mtDNA than autosomal DNA between northern and southern Zanzibar suggesting female philopatry with greater dispersal by males than females. Genetic diversity levels were relatively high in all areas and there were no indications of any recent reduction in effective population size, except in Mayotte where indications of a recent bottleneck encourage further analyses. Further, the close relationship and lack of clear structuring, with several shared haplotypes among regions, suggest a relatively recent common founder population for the Indo-Pacific bottlenose dolphins in the western Indian Ocean. Based on the high differentiation in mtDNA between northern and southern Zanzibar and that local growth rates in large part will be determined by female breeding success, we suggest that the Indo-Pacific bottlenose dolphins off northern and southern Zanzibar should be treated as separate management units.
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| 34. |
- Wallén, Johan, et al.
(author)
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Context-dependent demographic and genetic effects of translocation from a captive breeding project
- 2023
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In: Animal Conservation. - : Wiley. - 1367-9430 .- 1469-1795. ; 26:3, s. 412-423
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Journal article (peer-reviewed)abstract
- Translocations are a widespread approach to conserve threatened populations. Given the rapid decline and genetic deterioration of many natural populations, translocations are expected to become even more common in the future. The success of translocations is, however, dependent on multiple context-dependent factors, such as demographic and genetic status, habitat quality and animal behaviour. The Scandinavian arctic fox (Vulpes lagopus) exists in a small, fragmented population that is demographically vulnerable and exposed to inbreeding depression. In the early 2000 s, releases of arctic foxes from the Norwegian Captive Breeding Programme were initiated with the purpose of reintroducing populations to formerly inhabited areas and promoting connectivity. Since 2008/2009, 61 foxes have been released in Junkeren, Norway to re-establish an unoccupied area. We used a combination of field observations and microsatellite genotyping from the release site and two neighbouring subpopulations to investigate (i) the probability of establishment and reproduction for released foxes at the release site and in neighbouring subpopulations, and (ii) the impact on litter size and genetic composition in the recipient populations. Results showed that 18% of the released foxes were established at the release site, or in neighbouring subpopulations and 11.5% reproduced successfully. The extent of post-release dispersal into neighbouring subpopulations was also relatively high (11.5%). During the study period, the number of litters more than doubled in the subpopulations with released foxes contributing 29.5% to this increase, but no clear effect of immigration on litter size was found. There was a slight increase in genetic variation in one of the subpopulations, and a significant decline in genetic divergence between subpopulations. We conclude that despite extensive releases, demographic and genetic effects were highly context-dependent. This study highlights the challenges of reinforcement programmes in small populations and reintroductions to unoccupied sites, especially for highly mobile species in a fragmented landscape.
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