Determinants of lemming outbreaks

Population outbreaks in tundra rodents have intrigued scientists for a century as a result of their spectacular appearances and their general lessons in ecology. One outstanding question that has led to competing hypotheses is why sympatric lemmings and voles differ in regularity and shape of their outbreaks. Lemming outbreaks may be lost for decades while vole populations maintain regular population cycles. Moreover, when lemming populations eventually irrupt, they do so more steeply than the vole populations. Norwegian lemmings exhibited a large-scale outbreak synchronously with gray-sided voles in Finnmark, northern Fennoscandia, during 2006 to 2007 for the first time in two decades. Analyses of spatial variability of this outbreak across altitudinal gradients allowed us to identify determinants of the contrasting lemming and vole dynamics. The steeper lemming outbreak trajectories were caused by breeding and population growth during winter, when nonbreeding vole populations consistently declined. The differently shaped lemming and vole outbreaks appear to result from a particular demographic tactic of lemmings that evolved as an adaptation to the long and cold Arctic–Alpine winters. The lemming outbreak amplitude increased with altitude and vole density, indicating that lemming outbreaks are jointly facilitated by low temperatures and apparent mutualism with voles mediated by shared predators. High sensitivity to variation in climate and predation is likely to be the reasons why lemmings have more erratic population dynamics than sympatric voles. The combination of continued climatic warming and dampened vole cycles is expected to further decrease the frequency, amplitude, and geographic range of lemming outbreaks in tundra ecosystems

snow cover camera traps

Records of snow cover at camera trap locations. See metadata file for more detailed description

Åtgärdsprogram för fjällräv, 2017–2021 : (Vulpes lagopus)

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.The arctic fox is classified as endangered in Sweden and critically endangeredin Norway. It was a common species on the mountain tundra during the 19thcentury, but the population declined severely at the end of the 19thcentury inresponse to intensive harvesting. The arctic fox was protected by Swedish law in 1928 and Norwegian law in 1930, but despite this, the population remains small. The reasons for non-recovery is connected to increased competition and predation from expanding red foxes, irregular lemming cycles and the small population size itself. In addition to this, inbreeding depression has been documented in one of the sub-populations. Further threats are introduction of diseases and parasites as well as disturbance from human activities. In 2015, a minimum of 240 reproducing adults were recorded in Sweden and Norway altogether. Within the European Union, the arctic fox is a priority species according to the Habitat Directive. In Sweden, the arctic fox is a protected species according to “Species protection ordinance” (2007). In Norway, the population is protected after the “Regulation on the arctic fox as a priority species” (2015) according to the “Biodiversity Act” (2009). During 1998–2008, conservation actions in the form of monitoring, red fox culling and supplementary feeding was implemented in Sweden and Finland within the EU-Life funded project SEFALO+. During 2008–2012, red fox removal and supplementary feeding was financed through the Swedish action plan. In Norway, conservation actions started in 2004, financed by the Norwegian Environment Agency (previously Norwegian Directorate for Nature Management). Since then, a combination of action has been implemented in the different subpopulations, including captive breeding and release of juveniles (since 2006), supplementary feeding and red fox control. Within the EU-Interreg project “Felles Fjellrev” (2010–2013) increased actions were conducted in the county of Jämtland as well as Nord- and Sør- Trøndelag, specifically focusing on smaller mountain areas located between the core areas. In 2015, Sweden and Norway signed an agreement with the aim of strengthening the collaboration for arctic fox conservation. To reach a viable population, we recommend that the actions continue within the framework of this Swedish-Norwegian action plan (2017–2021). The vision of this plan is to reach a viable Scandinavian arctic fox population without need for further conservation actions. This action plan emphasizes the importance of continuing the central actions of supplementary feeding and red fox control. In addition, we will include actions directed towards the factors underlying red fox expansion. Captive breeding and re-introduction, alternatively translocations, are suggested to demographically strengthen small populations, increase chances of establishment in stepping stone areas, and reduce occurrence of inbreeding. The health status of populations will be monitored and in case of disease outbreaks, appropriate treatment will be undertaken. Specific information campaigns will be designed to reduce conflicts and disturbance from human activities. The action plan is a guiding, but not legally binding document. The cost for the conservation measures, to be funded from the SEPA’s allocation for action plans in Sweden and Norway is estimated at 1 570 504 € and 4 945 814 € respectively during the actions plans’ validity period 2017–2021

Åtgärdsprogram för fjällräv, 2017–2021 : (Vulpes lagopus)

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.The arctic fox is classified as endangered in Sweden and critically endangeredin Norway. It was a common species on the mountain tundra during the 19thcentury, but the population declined severely at the end of the 19thcentury inresponse to intensive harvesting. The arctic fox was protected by Swedish law in 1928 and Norwegian law in 1930, but despite this, the population remains small. The reasons for non-recovery is connected to increased competition and predation from expanding red foxes, irregular lemming cycles and the small population size itself. In addition to this, inbreeding depression has been documented in one of the sub-populations. Further threats are introduction of diseases and parasites as well as disturbance from human activities. In 2015, a minimum of 240 reproducing adults were recorded in Sweden and Norway altogether. Within the European Union, the arctic fox is a priority species according to the Habitat Directive. In Sweden, the arctic fox is a protected species according to “Species protection ordinance” (2007). In Norway, the population is protected after the “Regulation on the arctic fox as a priority species” (2015) according to the “Biodiversity Act” (2009). During 1998–2008, conservation actions in the form of monitoring, red fox culling and supplementary feeding was implemented in Sweden and Finland within the EU-Life funded project SEFALO+. During 2008–2012, red fox removal and supplementary feeding was financed through the Swedish action plan. In Norway, conservation actions started in 2004, financed by the Norwegian Environment Agency (previously Norwegian Directorate for Nature Management). Since then, a combination of action has been implemented in the different subpopulations, including captive breeding and release of juveniles (since 2006), supplementary feeding and red fox control. Within the EU-Interreg project “Felles Fjellrev” (2010–2013) increased actions were conducted in the county of Jämtland as well as Nord- and Sør- Trøndelag, specifically focusing on smaller mountain areas located between the core areas. In 2015, Sweden and Norway signed an agreement with the aim of strengthening the collaboration for arctic fox conservation. To reach a viable population, we recommend that the actions continue within the framework of this Swedish-Norwegian action plan (2017–2021). The vision of this plan is to reach a viable Scandinavian arctic fox population without need for further conservation actions. This action plan emphasizes the importance of continuing the central actions of supplementary feeding and red fox control. In addition, we will include actions directed towards the factors underlying red fox expansion. Captive breeding and re-introduction, alternatively translocations, are suggested to demographically strengthen small populations, increase chances of establishment in stepping stone areas, and reduce occurrence of inbreeding. The health status of populations will be monitored and in case of disease outbreaks, appropriate treatment will be undertaken. Specific information campaigns will be designed to reduce conflicts and disturbance from human activities. The action plan is a guiding, but not legally binding document. The cost for the conservation measures, to be funded from the SEPA’s allocation for action plans in Sweden and Norway is estimated at 1 570 504 € and 4 945 814 € respectively during the actions plans’ validity period 2017–2021

camera trap data

A dataset of collected by nine below-snow camera traps. See metadata file for detailed description

Indirect food web interactions mediated by predator–rodent dynamics: relative roles of lemmings and voles

Production cycles in birds are proposed as prime cases of indirect interactions in food webs. They are thought to be driven by predators switching from rodents to bird nests in the crash phase of rodent population cycles. Although rodent cycles are geographically widespread and found in different rodent taxa, bird production cycles appear to be most profound in the high Arctic where lemmings dominate. We hypothesized that this may be due to arctic lemmings inducing stronger predator responses than boreal voles. We tested this hypothesis by estimating predation rates in dummy bird nests during a rodent cycle in low-Arctic tundra. Here, the rodent community consists of a spatially variable mix of one lemming (Lemmus lemmus) and two vole species (Myodes rufocanus and Microtus oeconomus) with similar abundances. In consistence with our hypothesis, lemming peak abundances predicted well crash-phase nest predation rates, whereas the vole abundances had no predictive ability. Corvids were found to be the most important nest predators. Lemmings appear to be accessible to the whole predator community which makes them particularly powerful drivers of food web dynamics

Data from: Transferability of biotic interactions: temporal consistency of arctic plant-rodent relationships is poor

Variability in biotic interaction strength is an integral part of food web functioning. However, the consequences of the spatial and temporal variability of biotic interactions are poorly known, in particular for predicting species abundance and distribution. The amplitude of rodent population cycles (i.e. peak phase abundances) has been hypothesized to be determined by vegetation properties in tundra ecosystems. We assessed the spatial and temporal predictability of food and shelter plants effects on peak phase small rodent abundance during two consecutive rodent population peaks. Rodent abundance was related to both food and shelter biomass during the first peak, and spatial transferability was mostly good. Yet, the temporal transferability of our models to the next population peak was poorer. Plant-rodent interactions are thus temporally variable and likely more complex than simple one-directional (bottom up) relationships or variably overruled by other biotic interactions and abiotic factors. We propose that parametrizing a more complete set of functional links within food webs across abiotic and biotic contexts would improve transferability of biotic interaction models. Such attempts are currently constrained by the lack of data with replicated estimates of key players in food webs. Enhanced collaboration between researchers whose main research interests lay in different parts of the food web could ameliorate this

Fjellrev i Finnmark : forskning og tiltak 2006

Faglig årsrapport for 2006 til DN