| 1. |
- Angerbjörn, Anders, et al.
(författare)
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Carnivore conservation in practice : replicatedmanagement actions on a large spatial scale
- 2013
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Ingår i: Journal of Applied Ecology. - : Wiley. - 0021-8901 .- 1365-2664. ; 50:1, s. 59-67
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Tidskriftsartikel (refereegranskat)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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| 2. |
- Elmhagen, Bodil, et al.
(författare)
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Åtgärdsprogram för fjällräv, 2017–2021 : (Vulpes lagopus)
- 2017
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Fjällräven är klassificerad som starkt hotad i Sverige och akut hotad i Norge. På 1800-talet var det en vanligt förekommande art, men till följd av intensivt jakttryck reducerades populationen kraftigt i slutet av 1800-talet. Fjällräven fridlystes 1928 i Sverige och 1930 i Norge. Trots skydd har populationen inte återhämtat sig. Detta beror på ett flertal samverkande faktorer, framförallt låg populationsstorlek, ökad konkurrens från rödrävar som expanderar in i fjällvärlden, samt uteblivna eller mer oregelbundna lämmeltoppar som leder till födobrist. Dessutom har inavel och inavelsdepression med ökad dödlighet och minskad reproduktion dokumenterats i vissa delbestånd. Sjukdomar och parasiter utgör ett ytterligare hot mot de små delpopulationernas fortlevnad. Störningar från mänskliga aktiviteter kan utgöra ytterligare bidragande faktorer.År 2015 fanns omkring 240 reproducerande vuxna fjällrävar i Sverige och Norge, vilket utgör ett mått på beståndets minimala storlek. Inom EU är fjällräven en prioriterad art enligt habitatdirektivet, i Sverige är fjällräven fridlyst enligt artskyddsförordningen, och i Norge är fjällräven skyddad med ”fjällrävförskriften” enligt naturmangfoldloven.Åtgärder för att rädda fjällräven genomfördes i Sverige och Finland under 1998–2002 genom EU-Life Nature projektet SEFALO. Projektet fortsatte i en andra fas, SEFALO+ (2003–2008) som även involverade Norge. Båda projekten inkluderade åtgärder som stödutfodring, rödrävsjakt och inventeringar. I Norge startade flera åtgärder 2004 på uppdrag av Miljødirektoratet (tidigare Direktoratet for naturforvaltning). Sedan dess har en kombination av åtgärder genomförts i olika delbestånd: avel och utsättning av valpar, stödutfodring, samt kontroll av rödrävsbestånden. Avelsprojekt för fjällräv startade 2005 och de första valparna sattes ut 2006. Inom EU-Interregprojektet Felles Fjellrev (2010–2013) genomfördes utvidgade åtgärder i Jämtlands län samt Nord- och Sør-Trøndelag, med riktade åtgärder i mindre fjällområden mellan de fyra större delbestånden av fjällräv.För att fjällrävsstammen ska återuppnå en gynnsam bevarandestatus bör bevarandeåtgärderna fortsätta inom ramen för det svensk-norska åtgärdsprogrammet. Den långsiktiga visionen är att skapa en stabil och livskraftig stam med gynnsam bevarandestatus utan behov av ytterligare åtgärder. Det är emellertid långt tills denna vision uppnås och i detta program definieras konkreta målsättningar på lång (2035) och kort (2021) sikt. I detta program föreslås fortsatt genomförande av centrala åtgärder i form av stödutfodring och rödrävskontroll. Dessutom ska orsakerna till rödrävens ökade förekomst på fjället hanteras genom åtgärder mot de faktorer som gynnar expansionen. Avel och utsättning från det norska avelsprojektet, alternativt translokering av rävar mellan delpopulationerna, föreslås som åtgärd för att förstärka små populationer, etablera fjällrävar i mellanområden samt minska graden av inavel. Populationernas hälsostatus bör övervakas och vid ett utbrott ska behandling sättas in. Riktade informationskampanjer ska utformas för att minska konflikt och störning med människan.De åtgärder som förutsätts finansieras av Naturvårdsverket och Miljødirektoratet för genomförande av åtgärdsprogram för hotade arter beräknas totalt uppgå till 15, 1 miljoner kronor respektive 47,6 miljoner kronor under programmets giltighetsperiod 2017–2021.
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| 3. |
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| 4. |
- Herfindal, Ivar, et al.
(författare)
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Population persistence in a landscape context : the case of endangered arctic fox populations in Fennoscandia
- 2010
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Ingår i: Ecography. - : Wiley. - 0906-7590 .- 1600-0587. ; 33:5, s. 932-941
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Tidskriftsartikel (refereegranskat)abstract
- Anthropogenic fragmentation of habitat and populations is recognized as one of the most important factors influencing loss of biodiversity. Since it is difficult to quantify demographic parameters in small populations, we need alternative methods to elucidate important factors affecting the viability of local populations. The Fennoscandian arctic fox inhabits a naturally fragmented alpine tundra environment, but historic anthropogenic impacts have further fragmented its distribution. After almost 80 yr of protection, the population remains critically endangered. Both intrinsic factors (related to the isolation and size of sub-populations) and extrinsic factors (related to environmental conditions influencing patch quality and interspecific competition) have been proposed as explanations for the lack of population growth. To distinguish between these hypotheses, we conducted a spatially explicit analysis that compares areas where the species has persisted with areas where it has become locally extinct. We used characteristics of the fragments of alpine tundra habitat and individual arctic fox breeding dens (including both currently active dens and historically active dens) within the fragments to evaluate the importance of habitat characteristics and connectivity in explaining variation in persistence within a fragment. The number of reproductive events in a fragment was related to the size of the fragment, but not more than expected following a 1:1 relationship, suggesting little effect of fragment size on the relative number of reproductions. The likelihood of a den being used for breeding was positively associated with factors minimising interspecific competition as well as increasing within-fragment connectivity. These results support the idea that the failure of Fennoscandian arctic fox to recover is caused by demographic factors that can be related to fine-scale Allee or Allee-like effects, as well as environmental influences related to increased competition and exclusion by red foxes
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| 5. |
- Le Vaillant, Maryline, et al.
(författare)
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Spatial distribution in Norwegian lemming Lemmus lemmus in relation to the phase of the cycle
- 2018
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Ingår i: Polar Biology. - : Springer Science and Business Media LLC. - 0722-4060 .- 1432-2056. ; 41:7, s. 1391-1403
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Tidskriftsartikel (refereegranskat)abstract
- Competition between individuals of the same or different species affects spatial distribution of organisms at any given time. Consequently, a species geographical distribution is related to population dynamics through density-dependent processes. Small Arctic rodents are important prey species in many Arctic ecosystems. They commonly show large cyclic fluctuations in abundance offering a potential to investigate how landscape characteristics relates to density-dependent habitat selection. Based on long-term summer trapping data of the Norwegian lemming (Lemmus lemmus) in the Scandinavian Mountain tundra, we applied species distribution modeling to test if the effect of environmental variables on lemming distribution changed in relation to the lemming cycle. Lemmings were less habitat specific during the peak phase, as their distribution was only related to primary productivity. During the increase phase, however, lemming distribution was, in addition, associated with landscape characteristics such as hilly terrain and slopes that are less likely to get flooded. Lemming habitat use varied during the cycle, suggesting density-dependent changes in habitat selection that could be explained by intraspecific competition. We believe that the distribution patterns observed during the increase phase show a stronger ecological signal for habitat preference and that the less specific habitat use during the peak phase is a result of lemmings grazing themselves out of the best habitat as the population grows. Future research on lemming winter distribution would make it possible to investigate the year around strategies of habitat selection in lemmings and a better understanding of a fundamental actor in many Arctic ecosystems.
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| 6. |
- Meijer, Tomas, et al.
(författare)
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Life history traits in a cyclic ecosystem : a field experiment on the arctic fox
- 2013
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Ingår i: Oecologia. - : Springer Science and Business Media LLC. - 0029-8549 .- 1432-1939. ; 173:2, s. 439-447
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Tidskriftsartikel (refereegranskat)abstract
- The reproduction of many species depends strongly on variation in food availability. The main prey of the arctic fox in Fennoscandia are cyclic small rodents, and its number of litters and litter size vary depending on the phase of the rodent cycle. In this experiment, we studied if the arctic fox adjusts its reproduction as a direct response to food abundance, in accordance with the food limitation hypothesis, or if there are additional phase-dependent trade-offs that influence its reproduction. We analysed the weaning success, i.e. proportion of arctic fox pairs established during mating that wean a litter in summer, of 422 pairs of which 361 were supplementary winter fed, as well as the weaned litter size of 203 litters of which 115 were supplementary winter fed. Females without supplementary winter food over-produced cubs in relation to food abundance in the small rodent increase phase, i.e. the litter size was equal to that in the peak phase when food was more abundant. The litter size for unfed females was 6.38 in the increase phase, 7.11 in the peak phase and 3.84 in the decrease phase. The litter size for supplementary winter-fed litters was 7.95 in the increase phase, 10.61 in the peak phase and 7.86 in the decrease phase. Thus, feeding had a positive effect on litter size, but it did not diminish the strong impact of the small rodent phase, supporting phase-dependent trade-offs in addition to food determining arctic fox reproduction.
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| 7. |
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| 8. |
- Norén, Karin, et al.
(författare)
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From monogamy to complexity : social organization of arctic foxes (Vulpes lagopus) in contrasting ecosystems
- 2012
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Ingår i: Canadian Journal of Zoology. - 0008-4301 .- 1480-3283. ; 90:9, s. 1102-1116
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Tidskriftsartikel (refereegranskat)abstract
- Canids display pronounced intraspecific variation in social organization, ranging from single breeding females to large and complex groups. Despite several hypotheses in this matter, little is understood about the ecological factors underlying this flexibility. We have used the arctic fox (Vulpes lagopus (L., 1758)) to investigate how contrasting ecosystem conditions concerning resources and predation influence group formation. We predicted that complex groups are more common in resource-rich ecosystems with predators, whereas simple groups occur in more marginal ecosystems without predators. Samples from 54 groups were collected from four populations of arctic foxes with contrasting prey resources and predation and these samples were genotyped in 10 microsatellite loci. We found considerable variation between ecosystems and a significant relationship between resources and formation of complex groups. We conclude that sufficient amounts of food is a prerequisite for forming complex groups, but that defense against predation further increases the benefits of living in larger groups. We present a conceptual model suggesting that a trade-off between the cost of resource depletion and the benefits obtained for guarding against predators explain the differences in social organization. The variable ecology of the arctic foxes makes it is a plausible model species for understanding the connection between ecology and social organization also in other species.
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