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  • 1.
    Angerbjörn, Anders
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Eide, Nina E.
    Dalén, Love
    Stockholm University, Faculty of Science, Department of Zoology.
    Elmhagen, Bodil
    Stockholm University, Faculty of Science, Department of Zoology.
    Hellström, Peter
    Stockholm University, Faculty of Science, Department of Zoology.
    Ims, Rolf A.
    Killengreen, Siw
    Landa, Arild
    Meijer, Tomas
    Stockholm University, Faculty of Science, Department of Zoology.
    Mela, Matti
    Niemimaa, Jukka
    Norén, Karin
    Stockholm University, Faculty of Science, Department of Zoology.
    Tannerfeldt, Magnus
    Stockholm University, Faculty of Science, Department of Zoology.
    Yoccoz, Nigel G.
    Henttonen, Heikki
    Carnivore conservation in practice: replicatedmanagement actions on a large spatial scale2013In: Journal of Applied Ecology, ISSN 0021-8901, E-ISSN 1365-2664, Vol. 50, no 1, p. 59-67Article in journal (Refereed)
    Abstract [en]

    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.

  • 2. Bergqvist, Göran
    et al.
    Paulson, Sam
    Elmhagen, Bodil
    Stockholm University, Faculty of Science, Department of Zoology.
    Effects of female body mass and climate on reproduction in northern wild boar2018In: Wildlife Biology, ISSN 0909-6396, E-ISSN 1903-220X, article id wlb.00421Article in journal (Refereed)
    Abstract [en]

    Mammalian life history strategies depend on climate conditions. Hence, reproductive parameters may vary regionally, and knowledge on such patterns are important for sustainable management. Wild boar research has been biased towards south and central Europe. Here we investigate the effects of mother's carcass mass, season and climate (summer temperature and precipitation as well as January temperature) on pregnancy rate and litter size in 601 free-ranging female wild boar from hemiboreal Sweden, close to the north border of wild boar distribution range in Europe. Pregnancy rate was on average 33.4 +/- 1.94% (mean +/- SE), whereas average litter size of pregnant females was 4.7 +/- 0.12. Pregnancy rate was highest during the seasonal reproduction peak in winter and spring, and both pregnancy rate and litter size increased significantly with increasing female body mass. The probability of a female being pregnant exceeded 50% when carcass mass exceeded 58 kg, equivalent to a live mass of 113 kg, and litter size increased by one for each 16 kg increase in female carcass mass. We found no significant effects of temporal variations in climate, and suggest that such variations were not sufficiently large to affect wild boar reproduction. Alternatively, the reproductive strategy of wild boar may be adjusted to prevailing regional climate conditions. In that case, other life history traits, such as mortality, may be more sensitive to short-term climate fluctuations. Wild boar management needs to take temporal variations in reproduction, as well as in resource availability, into consideration when deciding on prudent management actions.

  • 3.
    Dalerum, Fredrik
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Tannerfeldt, Magnus
    Stockholm University, Faculty of Science, Department of Zoology.
    Elmhagen, Bodil
    Stockholm University, Faculty of Science, Department of Zoology.
    Becker, Dennis
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    Distribution, morphology and use of arctic fox dens in Sweden2002In: Wildlife Biology, Vol. 8, no 3, p. 185-192Article in journal (Refereed)
    Abstract [en]

    Seventy-seven arctic fox dens in Vindelfjällen, Northern Sweden, are described with regard to distribution, morphology and fox use. The density of dens in the area was 1 den / 21 km2 and dens were more spaced than random. The dens were situated at a mean altitude ( sd) of 915  74 m.a.s.l., were on average 3.5  1.88 km from nearest tree line, had a mean number of 44  32 den openings and a mean area of 277  237 m2. During the 21 year study period, 31 dens were used by arctic foxes and 10 by red foxes. Number of den openings, den area, altitude and distance to nearest tree line explained 36 % of arctic fox den use (p < 0.001) and 21 % of red foxes use of arctic fox dens during the study period (p = 0.01). Arctic foxes used dens at higher altitude (p = 0.03) and further away from forest than red foxes did (p = 0.03), and tended to breed in dens with more den openings (p = 0.08). Arctic foxes used some breeding dens more frequently than others (p = 0.002). Among the breeding dens, both den use and litter size were positively related to den area (den use: p = 0.04; litter size: p < 0.001). Successful breeding dens for arctic foxes in Sweden thus appear to be characterised by large size and many openings, and they are situated far away from forest at relatively high altitudes.

  • 4.
    Dalén, Love
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Elmhagen, Bodil
    Stockholm University, Faculty of Science, Department of Zoology, Animal Ecology.
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology, Animal Ecology.
    DNA analysis on fox faeces and competition induced niche shifts2004In: Molecular Ecology, ISSN 0962-1083, Vol. 13, no 8, p. 2389-2392Article in journal (Refereed)
    Abstract [en]

    Interference competition can force inferior competitors to change their distribution patterns. It is, however, possible that the dominant competitor poses a higher threat during certain times of the year, for example during reproduction. In such cases, the inferior competitor is expected to change its distribution accordingly. We used a molecular species identification method on faeces to investigate how the spatial overlap between arctic and red foxes changes between seasons. The results show that arctic and red foxes are sympatric during winter, but allopatric in summer as arctic foxes retreat to higher altitudes further from the tree-line during the breeding season

  • 5.
    Dalén, Love
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Kvaloy, K.
    Linnell, J. D. C.
    Elmhagen, Bodil
    Stockholm University, Faculty of Science, Department of Zoology.
    Strand, O.
    Tannerfeldt, M.
    Henttonen, H.
    Fuglei, E.
    Landa, A.
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    Population structure in a critically endangered arctic fox population: does genetics matter?2006In: Molecular Ecology, ISSN 0962-1083, E-ISSN 1365-294X, Vol. 15, no 10, p. 2809-2819Article in journal (Refereed)
    Abstract [en]

    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.

  • 6.
    Elmhagen, Bodil
    Stockholm University, Faculty of Science, Department of Zoology. Zoologisk ekologi.
    Interference competition between arctic and red foxes.2003Doctoral thesis, monograph (Other academic)
    Abstract [en]

    In this thesis, I investigate the relationship between arctic foxes Alopex lagopus and red foxes Vulpes vulpes in Swedish mountain tundra habitat (fjällen). The arctic fox population was severely reduced by hunting in the early 20th century. It has not recovered despite protection since 1928 and it is endangered, while the red fox population increased in 1930-1960.

    I found a high food niche overlap between arctic and red foxes and they responded similarly to changes in the prey base, indicating similar prey preferences. Hence, arctic and red foxes should compete for the same territories; more precisely the ones in low altitude areas close to the tree-line where prey abundance is relatively high. In the 19th century, arctic foxes bred in all tundra habitats. An analysis of present den use showed that arctic foxes have retreated to higher altitudes as they rarely used the lower parts of their former range. Instead, red foxes did. Arctic foxes were highly dependent on the availability of Norwegian lemmings Lemmus lemmus for reproduction, while red foxes at lower altitudes had better access to alternative prey.

    Interference competition imply that there are behavioural interactions between competing species, e.g. fighting or predation, but interactions can also be more subtle and imply that inferior species avoid encounters with stronger competitors by changing their habitat use. Red foxes are larger than arctic foxes. Hence, they have an advantage in direct fights and arctic foxes may either be driven away from their dens when red foxes establish in the vicinity, or they avoid habitats where they risk encounters with red foxes. I found that arctic foxes almost exclusively used dens situated farther than 8 km from inhabited red fox dens. In two out of three cases when they bred closer to red foxes, there was red fox predation on arctic fox cubs. Further, simulations of arctic fox avoidance of areas surrounding inhabited red fox dens in a spatially explicit population model, indicated that relatively small numbers of red foxes might have a large impact on arctic fox population size and distribution.

    Thus, the results of this thesis indicate that interference competition with red foxes has hampered arctic fox recovery after the initial population decline, by causing a substantial reduction in arctic fox habitat. Further, red foxes have taken over the most productive areas and remaining arctic fox habitats is of such low quality that it is uncertain whether it can maintain even a small arctic fox population.

  • 7.
    Elmhagen, Bodil
    Stockholm University, Faculty of Science, Department of Zoology, Animal Ecology.
    Åtgärdsprogram för fjällräv 2008-2012 : (Vulpes lagopus) : hotkategori: akut hotad2009Report (Other academic)
  • 8.
    Elmhagen, B.odil
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    The applicability of metapopulation theory to large mammals2001In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 94, no 1, p. 89-100Article in journal (Refereed)
    Abstract [en]

    Metapopulation theory has become a common framework in conservation biology and it is sometimes suggested that a metapopulation approach should be used for management of large mammals. However. it has also been suggested that metapopulation theory would not be applicable to species with long generations compared to those with short ones. In this paper, we review how and on what empirical ground metapopulation terminology liar, been applied to insects, small mammals and large mammals, The review showed that the metapopulation term sometimes was used for population networks which only fulfilled the broadest possible definition of a metapopulation, i.e. they were subpopulations connected by migrating individuals. We argue that the metapopulation concept should be reserved for networks that also show some kind of metapopulation dynamics. Otherwise it applies to almost all populations and loses its substance. We found much empirical support for metapopulation dynamics in both insects and small mammals, but not in large mammals. A me possible reason is the methods used to confirm the existence of metapopulation dynamics, For insects and small mammals, the common approach is to study population turnover through patch occupancy data. Such data is difficult to obtain for large mammals, since longer temporal scales need to be covered to record extinctions and colonizations. Still, many populations of large mammals are exposed to habitat fragmentation and the resulting subpopulations sometimes have high risks of extinction. If there is migration between the subpopulations, the metapopulation framework could provide valuable information on their population dynamics. We suggest that a metapopulation approach can be interesting for populations of large mammals. when there are discrete breeding subpopulations and when these subpopulations have different growth rates and demographic fates. Thus, a comparison of the subpopulations' demographic fates, rather than subpopulation turnover, can be a feasible alternative for studies of metapopulation dynamics in large mammals.

  • 9.
    Elmhagen, Bodil
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Berteaux, Dominique
    Burgess, Robert M.
    Ehrich, Dorothee
    Gallant, Daniel
    Henttonen, Heikki
    Ims, Rolf A.
    Killengreen, Siw T.
    Niemimaa, Jukka
    Norén, Karin
    Stockholm University, Faculty of Science, Department of Zoology.
    Ollila, Tuomo
    Rodnikova, Anna
    Sokolov, Alexandrs A.
    Sokolova, Natasha A.
    Stickney, Alica A.
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    Homage to Hersteinsson and Macdonald: climate warming and resource subsidies cause red fox range expansion and Arctic fox decline2017In: Polar Research, ISSN 0800-0395, E-ISSN 1751-8369, Vol. 36, no suppl. 1, article id 3Article, review/survey (Refereed)
    Abstract [en]

    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.

  • 10.
    Elmhagen, Bodil
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Destouni, Georgia
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    Borgström, Sara
    Stockholm University, Faculty of Science, Stockholm Resilience Centre.
    Boyd, Emily
    Stockholm University, Faculty of Science, Stockholm Resilience Centre. University of Reading, England.
    Cousins, Sara A. O.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Dalen, Love
    Ehrlén, Johan
    Stockholm University, Faculty of Science, Department of Physical Geography. Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Ermold, Matti
    Hambäck, Peter A.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Hedlund, Johanna
    Stockholm University, Faculty of Science, Department of Zoology.
    Hylander, Kristoffer
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Jaramillo, Fernando
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Lagerholm, Vendela K.
    Stockholm University, Faculty of Science, Department of Zoology. Swedish Museum of Natural History, Sweden.
    Lyon, Steve W.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Moor, Helen
    Stockholm University, Faculty of Science, Stockholm Resilience Centre.
    Nykvist, Björn
    Stockholm University, Faculty of Science, Stockholm Resilience Centre. Stockholm University, Stockholm Environment Institute.
    Pasanen-Mortensen, Marianne
    Stockholm University, Faculty of Science, Department of Zoology.
    Plue, Jan
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Prieto, Carmen
    Stockholm University, Faculty of Science, Department of Physical Geography.
    van der Velde, Ype
    Stockholm University, Faculty of Science, Department of Physical Geography. Wageningen University & Research Center, Netherlands.
    Lindborg, Regina
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Interacting effects of change in climate, human population, land use, and water use on biodiversity and ecosystem services2015In: Ecology & society, ISSN 1708-3087, E-ISSN 1708-3087, Vol. 20, no 1, article id UNSP 23Article in journal (Refereed)
    Abstract [en]

    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.

  • 11.
    Elmhagen, Bodil
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Eide, Nina E.
    Norén, Karin
    Stockholm University, Faculty of Science, Department of Zoology.
    Killengreen, Siw T.
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    Wallén, Johan
    Stockholm University, Faculty of Science, Department of Zoology.
    Åtgärdsprogram för fjällräv, 2017–2021 (Vulpes lagopus): Hotkategori: Starkt hotad EN2017Report (Other academic)
  • 12.
    Elmhagen, Bodil
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Eriksson, Ove
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Lindborg, Regina
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Implications of climate and land-use change for landscape processes, biodiversity, ecosystem services, and governance2015In: Ambio, ISSN 0044-7447, E-ISSN 1654-7209, Vol. 44, p. s1-S5Article in journal (Refereed)
    Abstract [en]

    This introduction to the Special Issue summarizes the results of 14 scientific articles from the interdisciplinary research program Ekoklim at Stockholm University, Sweden. In this program, we investigate effects of changing climate and land use on landscape processes, biodiversity, and ecosystem services, and analyze issues related to adaptive governance in the face of climate and land-use change. We not only have a research focus on the 22 650 km(2) Norrstrom catchment surrounding lake Malaren in south-central Sweden, but we also conduct research in other Swedish regions. The articles presented here show complex interactions between multiple drivers of change, as well as feedback processes at different spatiotemporal scales. Thus, the Ekoklim program highlights and deals with issues relevant for the future challenges society will face when land-use change interacts with climate change.

  • 13.
    Elmhagen, Bodil
    et al.
    Stockholm University, Faculty of Science, Department of Zoology, Animal Ecology.
    Hellström, Peter
    Stockholm University, Faculty of Science, Department of Zoology, Animal Ecology.
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology, Animal Ecology.
    Kindberg, Jonas
    Changes in vole and lemming fluctuations in northern Sweden 1960-2008 revealed by fox dynamics2011In: Annales Zoologici Fennici, ISSN 0003-455X, E-ISSN 1797-2450, Vol. 48, no 3, p. 167-179Article in journal (Refereed)
    Abstract [en]

    Cyclic dynamics with extensive spatial synchrony has long been regarded as characteristic of key herbivores at high latitudes. This contrasts to recent reports of fading cycles in arvicoline rodents in boreal and alpine Fennoscandia. We investigate the spatio-temporal dynamics of boreal red fox and alpine arctic fox in Sweden as a proxy for the dynamics of their main prey, voles and Norwegian lemming, respectively. We analyse data from five decades, 1960-2008, with wavelets and autocorrelation approaches. Cyclic dynamics were identified with at least one method in all populations (arctic fox n = 3, red fox n = 6). The dynamics were synchronous between populations, or coupled with a 1-yr lag, in 8 of 13 pairwise comparisons. Importantly though, the dynamics were heterogeneous in space and time. All analytical approaches identified fading cycles in the three arctic fox populations and two northern red fox populations. At least one method identified similar patterns in three southern red fox populations. Red fox dynamics were cyclic in the 1970s primarily, while arctic fox dynamics was cyclic until the late 1980s or early 1990s. When cyclic, 4-yr cycles dominated in arctic fox and northern red fox, whilst 3-4-yr cycles was found in southern red foxes. Significant cyclic regimes reappeared in the 1990s or 2000s in two red fox populations and one arctic fox population. Cycles and regionally coupled dynamics appeared associated in northern arctic and red foxes. This study supports accumulating evidence which suggests that cyclic and synchronous patterns in the dynamics of lemmings and voles are nonstationary in space and time. Furthermore, the similar patterns of change in both fox species indicate that persistence of cycles is governed by similar mechanisms in lemmings and voles.

  • 14.
    Elmhagen, Bodil
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Hersteinsson, Páll
    Norén, Karin
    Stockholm University, Faculty of Science, Department of Zoology.
    Unnsteinsdottir, Ester R.
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    From breeding pairs to fox towns: the social organisation of arctic fox populations with stable and fluctuating availability of food2014In: Polar Biology, ISSN 0722-4060, E-ISSN 1432-2056, Vol. 37, no 1, p. 111-122Article in journal (Refereed)
    Abstract [en]

    Food availability can impact group formation in Carnivora. Specifically, it has been suggested that temporal variation in food availability may allow a breeding pair to tolerate additional adults in their territory at times when food abundance is high. We investigate group occurrence and intraspecific tolerance during breeding in a socially flexible canid, the arctic fox (Vulpes lagopus). We compare Iceland and Sweden where resource conditions differ considerably. A breeding pair was the most common social unit in both populations, but as predicted, groups were more frequent where food abundance varied substantially between years (Sweden: 6 %) than where food availability was stable (Iceland: ≤2 %). Within Sweden, supplemental feeding increased group occurrence from 6 to 21 %, but there was no effect of natural variation in lemming (Lemmus lemmus) availability since group formation was rare also at lemming highs. Thus, additional factors appeared to influence the trade-off between intraspecific territoriality and tolerance. We report two cases where related females showed enduring social relationships with good-neighbour strategies. Related females also engaged in alloparental behaviour in a ‘fox town’ with 31 foxes (4 adults, 3 litters). In contrast, when unrelated foxes bred close to each other, they moved or split their litters during summer, presumably because of territorial conflict. We suggest that fluctuating food availability is linked to group formation in this Arctic carnivore, but also when food availability increases, additional factors such as relatedness, alloparental benefits, competition and predator defence appear necessary to explain group formation.

  • 15.
    Elmhagen, Bodil
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Kindberg, Jonas
    Hellström, Peter
    Stockholm University, Faculty of Science, Department of Zoology.
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    A boreal invasion in response to climate change?: Range shifts and community effects in the borderland between forest and tundra2015In: Ambio, ISSN 0044-7447, E-ISSN 1654-7209, Vol. 44, no 1, p. 39-50Article in journal (Refereed)
    Abstract [en]

    It has been hypothesized that climate warming will allow southern species to advance north and invade northern ecosystems. We review the changes in the Swedish mammal and bird community in boreal forest and alpine tundra since the nineteenth century, as well as suggested drivers of change. Observed changes include (1) range expansion and increased abundance in southern birds, ungulates, and carnivores; (2) range contraction and decline in northern birds and carnivores; and (3) abundance decline or periodically disrupted dynamics in cyclic populations of small and medium-sized mammals and birds. The first warm spell, 1930-1960, stands out as a period of substantial faunal change. However, in addition to climate warming, suggested drivers of change include land use and other anthropogenic factors. We hypothesize all these drivers interacted, primarily favoring southern generalists. Future research should aim to distinguish between effects of climate and land-use change in boreal and tundra ecosystems.

  • 16.
    Elmhagen, Bodil
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Ludwig, Gilbert
    University of Jyväskylä, Finland.
    Rushton, Steve
    Newcastle University, UK.
    Helle, Pekka
    Finnish Game and Fisheries and Research Institute, Finland.
    Lindén, Harto
    Finnish Game and Fisheries and Research Institute, Finland.
    Top predators, mesopredators and their prey: interference ecosystems along bioclimatic productivity gradients2010In: Journal of Animal Ecology, ISSN 0021-8790, E-ISSN 1365-2656, Vol. 79, no 4, p. 785-794Article in journal (Refereed)
    Abstract [en]

    1. The Mesopredator Release Hypothesis (MRH) suggests that top predator suppression of mesopredators is a key ecosystem function with cascading impacts on herbivore prey, but it remains to be shown that this top-down cascade impacts the large-scale structure of ecosystems.

    2. The Exploitation Ecosystems Hypothesis (EEH) predicts that regional ecosystem structures are determined by top-down exploitation and bottom-up productivity. In contrast to MRH, EEH assumes that interference among predators has a negligible impact on the structure of ecosystems with three trophic levels.

    3. We use the recolonisation of a top predator in a three-level boreal ecosystem as a natural experiment to test if large-scale biomass distributions and population trends support MRH. Inspired by EEH, we also test if top-down interference and bottom-up productivity impact regional ecosystem structures.

    4. We use data from the Finnish Wildlife Triangle Scheme which has monitored top predator (lynx Lynx lynx), mesopredator (red fox Vulpes vulpes) and prey (mountain hare Lepus timidus) abundance for 17 years in a 200 000 km2 study area which covers a distinct productivity gradient.

    5. Fox biomass was lower than expected from productivity where lynx biomass was high, while hare biomass was lower than expected from productivity where fox biomass was high. Hence, where interference controlled fox abundance, lynx had an indirect positive impact on hare abundance as predicted by MRH. The rates of change indicated that lynx expansion gradually suppressed fox biomass.

    6. Lynx status caused shifts between ecosystem structures. In the “interference ecosystem”, lynx and hare biomass increased with productivity whilst fox biomass did not. In the “mesopredator release ecosystem”, fox biomass increased with productivity but hare biomass did not. Thus, biomass controlled top-down did not respond to changes in productivity. This fulfils a critical prediction of EEH.

    7. We conclude that the cascade involving top predators, mesopredators and their prey can determine large-scale biomass distribution patterns and regional ecosystem structures. Hence, interference within trophic levels has to be taken into account to understand how terrestrial ecosystem structures are shaped.

  • 17.
    Elmhagen, Bodil
    et al.
    Newcastle University.
    Rushton, Steve
    Newcastle Univsersity.
    Trophic control of mesopredators in terrestrial ecosystems: top-down or bottom-up?2007In: Ecology Letters, ISSN 1461-023X, E-ISSN 1461-0248, Vol. 10, no 3, p. 197-206Article in journal (Refereed)
    Abstract [en]

    It has been argued that widespread extinctions of top predators have changed terrestrial ecosystem structures through mesopredator release, where increased abundances of medium-sized predators have detrimental effects on prey communities. This top-down concept has received much attention within conservation biology, but few studies have demonstrated the phenomenon. The concept has been criticized since alternative explanations involving bottom-up impacts from bioclimatic effects on ecosystem productivity and from anthropogenic habitat change are rarely considered. We analyse the response of a mesopredator (the red fox) to declines in top predators (wolf and Eurasian lynx) and agricultural expansion over 90 years in Sweden, taking bioclimatic effects into account. We show a top-down mesopredator release effect, but ecosystem productivity determined its strength. The impacts of agricultural activity were mediated by their effects on top predator populations. Thus, both top-down and bottom-up processes need to be understood for effective preservation of biodiversity in anthropogenically transformed ecosystems.

  • 18.
    Elmhagen, Bodil
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Tannerfeldt, M.
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    Food-niche overlap between arctic and red foxes2002In: Canadian Journal of Zoology, ISSN 0008-4301, E-ISSN 1480-3283, Vol. 80, no 7, p. 1274-1285Article in journal (Refereed)
    Abstract [en]

    Arctic foxes (Alopex lagopus) in Fennoscandia have retreated to higher altitudes on the mountain tundra, possibly because of increased competition with red foxes (Vulpes vulpes) at lower altitudes. In this study we compare summer food niches of the two species in mountain tundra habitat. Arctic foxes consumed lemmings more often than red foxes did, while red foxes consumed field voles and birds more often. Yet despite substantial variation in the diet of each species among summers, food-niche overlaps between the species were consistently high in most summers, as arctic and red foxes responded similarly to temporal changes in prey availability. Occurrences of field voles and birds in fox scats were negatively Correlated with altitude, while the occurrences of lemmings tended to increase with altitude. Since arctic foxes bred at higher altitudes than red foxes, the differences between arctic and red fox diets were better explained by altitudinal segregation than by differences between their fundamental food niches. Arctic foxes should therefore endeavour to use the more productive hunting grounds at the lower altitudes of their former range, but interference competition with red foxes might decrease their access to these areas, and consequently cause a decrease in the size of in their realised niche.

  • 19.
    Elmhagen, Bodil
    et al.
    Stockholm University, Faculty of Science, Department of Zoology. Zoologisk ekologi.
    Tannerfeldt, Magnus
    Stockholm University, Faculty of Science, Department of Zoology. Zoologisk ekologi.
    Verucci, Paolo
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology. Zoologisk ekologi.
    The arctic fox (Alopex lagopus) : an opportunistic specialist.2000In: Journal of Zoology, Vol. 251, no 2, p. 139-149Article in journal (Refereed)
    Abstract [en]

    Reliable and abundant resources are likely to favour specialisation, while unpredictable environmental variation should favour a generalist strategy. The rodent population cycles of northern latitudes can be seen as both predictable and unpredictable, depending on the scale in time and space. The arctic fox (Alopex lagopus) is an opportunistic carnivore, but paradoxically, it seems to function as a specialist on fluctuating rodent (Arvicolinae) populations in most inland areas. We have studied the dietary response of arctic foxes in Sweden during five years of varying abundance of Norwegian lemming (Lemmus lemmus), and how these changes influenced reproductive success of the foxes. The arctic fox population on mainland Fennoscandia is threatened by extinction and the situation has deteriorated during the 1980´s and 90´s, due to an absence of lemming peaks. Our results showed that in all years, lemming was the main prey for arctic foxes, with in total 85% frequency of occurrence in summer faeces (scats). Bird remains (mainly Passeriformes) were present in 34% of the scats, reindeer (Rangifer tarandus) in 21%, voles and shrews in 4% and hares (Lepus timidus) in 2% of the scats. The occurrences of lemming, bird and larger mammal (reindeer and hare) remains in the scats varied significantly between years. Temporal variations within summer seasons and dietary differences between subareas, indicated that arctic foxes fed opportunistically on the alternative prey types, when available. Den occupancy rates were positively correlated with lemming population densities during the previous winter, indicating a strong numerical response. We conclude that from a functional aspect, the arctic fox in Sweden is a lemming specialist, since lemming is the main prey and their abundance is the best predictor of arctic fox reproductive success. At the same time, other prey are used opportunistically in relation to their availability.

  • 20.
    Haage, Marianne
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    Elmhagen, Bodil
    Stockholm University, Faculty of Science, Department of Zoology.
    Maran, Tiit
    An experimental approach to the formation of diet preferences and individual specialisation in European mink2017In: European Journal of Wildlife Research, ISSN 1612-4642, E-ISSN 1439-0574, Vol. 63, no 2, p. 1-8, article id 34Article in journal (Refereed)
    Abstract [en]

    Individual dietary specialisation can occur within populations even when average diets suggest that the population has a generalist feeding strategy. Individual specialisation may impact fitness and has been related to demographic traits, ecological opportunity, competition, learning and animal personality. However, the causation and formation of individual specialisation are not fully understood. Experiments on animals raised in controlled environments provide an opportunity to examine dietary preferences and learning largely independent from variation in lifetime experiences and ecological opportunity. Here, we use a feeding experiment to examine individual specialisation and learning in captive bred European mink (Mustela lutreola) in an Estonian conservation programme. In a series of cafeteria experiments, animals could choose between one familiar food item (Baltic herring Clupea harengus membras) and two initially novel ones (noble crayfish Astacus astacus and house mouse Mus musculus). In general, mice were rarely eaten whilst crayfish consumption increased over time and fish decreased. At the individual level, there was a mix of generalists and crayfish or fish specialists, and the individuals differed in learning time in relation to novel prey. Our results indicate that individual variation in innate preferences and learning both contributes to individual diet specialisation. The differences in learning indicate individual variation in behavioural plasticity, which in turn can be related to personality. This could be of concern in conservation, as personality has been shown to affect survival in translocations.

  • 21.
    Haage, Marianne
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Maran, Tiit
    Alm Bergvall, Ulrika
    Stockholm University, Faculty of Science, Department of Zoology.
    Elmhagen, Bodil
    Stockholm University, Faculty of Science, Department of Zoology.
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    Evolutionary maintenance of personality – a field experiment on survival and personalityIn: Oecologia, ISSN 0029-8549, E-ISSN 1432-1939Article in journal (Refereed)
  • 22.
    Haage, Marianne
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Maran, Tiit
    Alm Bergvall, Ulrika
    Stockholm University, Faculty of Science, Department of Zoology.
    Elmhagen, Bodil
    Stockholm University, Faculty of Science, Department of Zoology.
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    The influence of spatiotemporal conditions and personality on survival in reintroductions-evolutionary implications2017In: Oecologia, ISSN 0029-8549, E-ISSN 1432-1939, Vol. 183, no 1, p. 45-56Article in journal (Refereed)
    Abstract [en]

    Personality exists in non-human animals and can impact fitness. There is, however, a shortage of empirical studies in certain areas within the field, and fundamental evolutionary theory on personality remains largely untested. For example, little is known on how variation in personality is maintained over evolutionary time. Theory suggests that fluctuating selection pressures due to spatiotemporal variation in conditions, e.g. food availability, is a possible mechanism and a few studies have shown that the success of different personality types varies with spatiotemporal conditions. However, it remains unknown whether different mechanisms can maintain personality within a species. Here we use a reintroduction programme for the critically endangered European mink (Mustela lutreola) to test whether multiple personality trait domains (boldness, exploration and sociability) affected survival in two different years and islands. This was done through pre-release personality tests and post-release radio-tracking monitoring. Survival was positively correlated with boldness, whereas the relationship with exploration was either negative or positive depending on year/island. The results show a complex relationship between personality and survival and suggest that exploration can be maintained over evolutionary time via spatiotemporal variation in conditions. However, in contrast to exploration, boldness did not vary spatiotemporally and sociability had no impact on survival. This indicates that different personality trait domains might be maintained by different mechanisms. To date, personality has been studied primarily within behavioural sciences, but through empirical findings we highlight the importance of personality also in ecology and conservation biology.

  • 23.
    Haage, Marianne
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Pasanen-Mortensen, Marianne
    Stockholm University, Faculty of Science, Department of Zoology.
    Sidorovich, Vadim
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    Elmhagen, Bodil
    Stockholm University, Faculty of Science, Department of Zoology.
    American mink in north-eastern Europe – abundances, population trends and dynamics in relation to the red fox and otterManuscript (preprint) (Other academic)
  • 24.
    Herfindal, Ivar
    et al.
    Norwegian University of Science and Technology.
    Linnell, John D. C.
    Norwegian Institute for Nature Research.
    Elmhagen, Bodil
    Stockholm University, Faculty of Science, Department of Zoology.
    Andersen, Roy
    Norwegian Institute for Nature Research.
    Eide, Nina E
    Norwegian Institute for Nature Research.
    Frafjord, Karl
    Tromsö University.
    Henttonen, Heikki
    Metla - Finnish Forest Research Institute.
    Kaikusalo, Asko
    Metla - Finnish Forest Research Institute.
    Mela, Matti
    Metsähallitus - Finnish Park and Forestry Service.
    Tannerfeldt, Magnus
    Swedish Polar Research Secretariat.
    Dalén, Love
    Swedish Museum of Natural History.
    Strand, Olav
    Norwegian Institute for Nature Research.
    Landa, Arild
    Norwegian Institute for Nature Research.
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    Population persistence in a landscape context: the case of endangered arctic fox populations in Fennoscandia2010In: Ecography, ISSN 0906-7590, E-ISSN 1600-0587, Vol. 33, no 5, p. 932-941Article in journal (Refereed)
    Abstract [en]

    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

  • 25.
    Khalil, Hussein
    et al.
    Stockholm University, Faculty of Science, Department of Zoology, Animal Ecology.
    Pasanen Mortensen, Marianne
    Stockholm University, Faculty of Science, Department of Zoology, Animal Ecology.
    Elmhagen, Bodil
    Stockholm University, Faculty of Science, Department of Zoology, Animal Ecology.
    The relationship between wolverine and larger predators, lynx and wolf, in a historical ecosystem context2014In: Oecologia, ISSN 0029-8549, E-ISSN 1432-1939, Vol. 175, no 2, p. 625-637Article in journal (Refereed)
    Abstract [en]

    Apex predators play an important role in shaping ecosystem structure. They may suppress smaller predators (mesopredators) but also subsidize scavengers via carrion provisioning. However, the importance of these interactions can change with ecosystem context. The wolverine (Gulo gulo) is a cold-adapted carnivore and facultative scavenger. It has a circumboreal distribution, where it could be either suppressed or subsidized by larger predators. In Scandinavia, the wolverine might interact with two larger predators, wolf (Canis lupus) and lynx (Lynx lynx), but human persecution decimated the populations in the nineteenth and early twentieth century. We investigated potential relationships between wolverine and the larger predators using hunting bag statistics from 15 Norwegian and Swedish counties in 1846-1922. Our best models showed a positive association between wolverine and lynx trends, taking ecological and human factors into account. There was also a positive association between year-to-year fluctuations in wolverine and wolf in the latter part of the study period. We suggest these associations could result from positive lynx-wolverine interactions through carrion provisioning, while wolves might both suppress wolverine and provide carrion with the net effect becoming positive when wolf density drops below a threshold. Wolverines could thus benefit from lynx presence and low-to-intermediate wolf densities.

  • 26. Kuijper, D. P. J.
    et al.
    Sahlén, E.
    Elmhagen, Bodil
    Stockholm University, Faculty of Science, Department of Zoology.
    Chamaillé-Jammes, S.
    Sand, H.
    Lone, K.
    Cromsigt, J. P. G. M.
    Paws without claws? Ecological effects of large carnivores in anthropogenic landscapes2016In: Proceedings of the Royal Society of London. Biological Sciences, ISSN 0962-8452, E-ISSN 1471-2954, Vol. 283, no 1841, article id 20161625Article in journal (Refereed)
    Abstract [en]

    Large carnivores are frequently presented as saviours of biodiversity and ecosystem functioning through their creation of trophic cascades, an idea largely based on studies coming primarily out of relatively natural landscapes. However, in large parts of the world, particularly in Europe, large carnivores live in and are returning to strongly human-modified ecosystems. At present, we lack a coherent framework to predict the effects of large carnivores in these anthropogenic landscapes. We review how human actions influence the ecological roles of large carnivores by affecting their density or behaviour or those of mesopredators or prey species. We argue that the potential for density-mediated trophic cascades in anthropogenic landscapes is limited to unproductive areas where even low carnivore numbers may impact prey densities or to the limited parts of the landscape where carnivores are allowed to reach ecologically functional densities. The potential for behaviourally mediated trophic cascades may be larger and more widespread, because even low carnivore densities affect prey behaviour. We conclude that predator-prey interactions in anthropogenic landscapes will be highly context-dependent and human actions will often attenuate the ecological effects of large carnivores. We highlight the knowledge gaps and outline a new research avenue to study the role of carnivores in anthropogenic landscapes.

  • 27.
    Larm, Malin
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Elmhagen, Bodil
    Stockholm University, Faculty of Science, Department of Zoology.
    Granquist, Sandra M.
    Brundin, Erika
    Stockholm University, Faculty of Science, Department of Zoology.
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    The role of wildlife tourism in conservation of endangered species: Implications of safari tourism for conservation of the Arctic fox in Sweden2018In: Human Dimensions of Wildlife, ISSN 1087-1209, E-ISSN 1533-158X, Vol. 23, no 3, p. 257-272Article in journal (Refereed)
    Abstract [en]

    There are both positive and negative impacts on wildlife associated with wildlife tourism. In Sweden, the endangered Arctic fox is subject to a growing tourist interest. In the Helags mountain region there are guided Arctic fox safari tours that provide visitors with information about the Arctic fox. A survey of five separate groups of visitors in the region revealed that knowledge about the status of Arctic foxes and awareness of the behavioral guidelines for Arctic fox encounters improved after participation in a safari tour and with increasing Arctic fox interaction. We propose a schematic model summarizing the diverse ways in which wildlife tourism affects wildlife and their relative importance for conservation. The Arctic fox population in Sweden is small and sensitive to disturbance, but the positive impacts of Arctic fox tourism seem to compensate for the negative and contribute to their conservation under the current level of tourism pressure.

  • 28.
    Le Vaillant, Maryline
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Erlandsson, Rasmus
    Stockholm University, Faculty of Science, Department of Zoology.
    Elmhagen, Bodil
    Stockholm University, Faculty of Science, Department of Zoology.
    Hörnfeldt, Birger
    Eide, Nina E.
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    Spatial distribution in Norwegian lemming Lemmus lemmus in relation to the phase of the cycle2018In: Polar Biology, ISSN 0722-4060, E-ISSN 1432-2056, Vol. 41, no 7, p. 1391-1403Article in journal (Refereed)
    Abstract [en]

    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.

  • 29.
    Meijer, Tomas
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Elmhagen, Bodil
    Stockholm University, Faculty of Science, Department of Zoology.
    Eide, Nina
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    Life history traits in a cyclic ecosystem– a field experiment on the arctic foxManuscript (preprint) (Other academic)
  • 30.
    Meijer, Tomas
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Elmhagen, Bodil
    Stockholm University, Faculty of Science, Department of Zoology.
    Eide, Nina E.
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    Life history traits in a cyclic ecosystem: a field experiment on the arctic fox2013In: Oecologia, ISSN 0029-8549, E-ISSN 1432-1939, Vol. 173, no 2, p. 439-447Article in journal (Refereed)
    Abstract [en]

    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.

  • 31.
    Meijer, Tomas
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Elmhagen, Bodil
    Stockholm University, Faculty of Science, Department of Zoology.
    Norén, Karin
    Stockholm University, Faculty of Science, Department of Zoology.
    Dahlgren, Johan
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    Reproductive strategy in a cyclic environmentManuscript (preprint) (Other academic)
    Abstract [en]

    The ability to maximize life-time reproductive output in relation to ecological variation in time and space is central for individual fitness. In cyclic environments the optimal litter size might vary over time depending on fluctuations in food abundance, offspring survival and their future fecundity. The arctic fox in Scandinavia is highly dependent on cyclic small rodents, such as lemmings and voles, for its reproduction. The arctic foxes can adjust their litter size in relation to small rodent phase, but this adjustment cannot be explained by food abundance only. In the rodent increase phase, litters are larger than expected from food abundance, while litters are smaller than expected in the decrease phase. In this paper, we studied how arctic fox litter size is associated with variation in the offspring reproductive value, specifically if the reproductive value is higher in the increase phase of the small rodent cycle. We followed the survival and fecundity, i.e. number of offspring, of 282 ear-tagged arctic foxes for a minimum of 4 years after birth in relation to small rodent phase. We found substantial variation in reproductive values, with a 3.2 times higher reproductive value for cubs born in the increase phase (0.74) compared to the decrease phase (0.23). The most pronounced difference in reproductive value between offspring born in different phases was caused by survival from birth to the end of their first year. Of the offspring born in the increase phase, 32% survived their first year compared to only 9% in the decrease phase. Our data supports that the observed phase dependent adjustment of arctic fox litter size has a demographic (and thereby an evolutionary) advantage by maximizing the number of offspring when the reproductive value is highest.

  • 32.
    Norén, Karin
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Hersteinsson, Pall
    Samelius, Gustaf
    Eide, Nina E.
    Fuglei, Eva
    Elmhagen, Bodil
    Stockholm University, Faculty of Science, Department of Zoology.
    Dalén, Love
    Stockholm University, Faculty of Science, Department of Zoology.
    Meijer, Tomas
    Stockholm University, Faculty of Science, Department of Zoology.
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    From monogamy to complexity: social organization of arctic foxes (Vulpes lagopus) in contrasting ecosystems2012In: Canadian Journal of Zoology, ISSN 0008-4301, E-ISSN 1480-3283, Vol. 90, no 9, p. 1102-1116Article in journal (Refereed)
    Abstract [en]

    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.

  • 33.
    Pasanen-Mortensen, Marianne
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Elmhagen, Bodil
    Stockholm University, Faculty of Science, Department of Zoology.
    Land cover effects on mesopredator abundance in the presence and absence of apex predators2015In: Acta Oecologica, ISSN 1146-609X, E-ISSN 1873-6238, Vol. 67, p. 40-48Article in journal (Refereed)
    Abstract [en]

    Trophic downgrading due to loss of apex consumers has been detected in many ecosystems. Loss of larger predators implies that medium-sized mesopredators rise to the status of apex predators which are limited bottom-up rather than top-down. Hence the density of medium-sized predators should be more strongly related to land cover in absence of larger predators. We investigate this hypothesis at a continental scale (Eurasia) for a medium-sized predator, the red fox Vulpes vulpes, in presence and absence of an apex predator, the Eurasian lynx Lynx lynx. We predicted that in absence of lynx, fox density should be positively associated with open land covers, as these could favour foxes due to high prey availability. Our results showed that fox abundance was independent of land cover in presence of lynx. However, in absence of lynx, fox density was positively but asymptotically related to cropland, while negatively related to grassland. Fox density was highest when cropland constituted approximately 30% of the landscape, likely reflecting an optimal composition of foraging and breeding habitat. Grassland was associated with low productivity, likely reflecting low prey availability. Thus, cropland is favourable for red fox, but only in absence of top-down limitation by lynx. We suggest that there are two ecosystem states in Eurasia, one northern where lynx is present as an apex predator, and one south-eastern where red fox assumes the apex predator position and its abundance is subsidised by anthropogenic land cover.

  • 34.
    Pasanen-Mortensen, Marianne
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Elmhagen, Bodil
    Stockholm University, Faculty of Science, Department of Zoology.
    Lindén, Harto
    Bergström, Roger
    Wallgren, Märtha
    van der Velde, Ype
    Cousins, Sara A. O.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    The changing contribution of top-down and bottom-up limitation of mesopredators during 220 years of land use and climate change2017In: Journal of Animal Ecology, ISSN 0021-8790, E-ISSN 1365-2656, Vol. 86, no 3, p. 566-576Article in journal (Refereed)
    Abstract [en]

    Apex predators may buffer bottom-up driven ecosystem change, as top-down suppression may dampen herbivore and mesopredator responses to increased resource availability. However, theory suggests that for this buffering capacity to be realized, the equilibrium abundance of apex predators must increase. This raises the question: will apex predators maintain herbivore/mesopredator limitation, if bottom-up change relaxes resource constraints? Here, we explore changes in mesopredator (red fox Vulpes vulpes) abundance over 220years in response to eradication and recovery of an apex predator (Eurasian lynx Lynx lynx), and changes in land use and climate which are linked to resource availability. A three-step approach was used. First, recent data from Finland and Sweden were modelled to estimate linear effects of lynx density, land use and winter temperature on fox density. Second, lynx density, land use and winter temperature was estimated in a 22650km(2) focal area in boreal and boreo-nemoral Sweden in the years 1830, 1920, 2010 and 2050. Third, the models and estimates were used to project historic and future fox densities in the focal area. Projected fox density was lowest in 1830 when lynx density was high, winters cold and the proportion of cropland low. Fox density peaked in 1920 due to lynx eradication, a mesopredator release boosted by favourable bottom-up changes - milder winters and cropland expansion. By 2010, lynx recolonization had reduced fox density, but it remained higher than in 1830, partly due to the bottom-up changes. Comparing 1830 to 2010, the contribution of top-down limitation decreased, while environment enrichment relaxed bottom-up limitation. Future scenarios indicated that by 2050, lynx density would have to increase by 79% to compensate for a projected climate-driven increase in fox density. We highlight that although top-down limitation in theory can buffer bottom-up change, this requires compensatory changes in apex predator abundance. Hence apex predator recolonization/recovery to historical levels would not be sufficient to compensate for widespread changes in climate and land use, which have relaxed the resource constraints for many herbivores and mesopredators. Variation in bottom-up conditions may also contribute to context dependence in apex predator effects.

  • 35.
    Pasanen-Mortensen, Marianne
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Pyykonen, Markku
    Elmhagen, Bodil
    Stockholm University, Faculty of Science, Department of Zoology.
    Where lynx prevail, foxes will fail - limitation of a mesopredator in Eurasia2013In: Global Ecology and Biogeography, ISSN 1466-822X, E-ISSN 1466-8238, Vol. 22, no 7, p. 868-877Article in journal (Refereed)
    Abstract [en]

    Aim Climate change and loss of apex predators can affect ecosystem structure and function through modified limitation processes. We investigated, on a continental scale, whether mesopredator abundance is limited from the top down by large predators, as predicted by the mesopredator release hypothesis, or by bottom-up factors. The mesopredator in focus is the red fox Vulpes vulpes, a key predator in many ecosystems due to its strong effects on prey abundance. Location Europe and northern Asia. Methods Data on red fox density were compiled from published papers and reports. For each site, we collated presence-absence data on large carnivores (Lynx lynx, Canis lupus, Canisaureus) and remote sensing data for factors potentially related to bottom-up limitation (winter severity, summer temperature, human density, primary productivity, tree cover). The data were analysed through structural equation modelling. Results The presence of lynx had a direct negative effect on red foxes, suppressing fox abundance. Also winter severity had a negative effect on red fox abundance, and in Eurasia as a whole this effect was partially mediated through lynx. Within the lynx distribution range, winter severity was the only bottom-up factor significantly affecting red fox abundance. Outside the lynx distribution range, primary productivity, summer temperature and human density had a positive effect on red fox abundance. Main conclusions Our results show that apex predators can limit mesopredator abundance on a continental scale, thus supporting the mesopredator release hypothesis. Winter severity also affected red fox abundance, partially due to an interaction between lynx and winter conditions. On the continental scale a complex network of processes operates with varying effects depending on mediation processes. Our results imply that apex predators can have an important effect on ecosystem structure by limiting mesopredator abundance, and we suggest that apex predators may dampen increases in mesopredator abundance driven by global warming.

  • 36. Ripple, William J.
    et al.
    Estes, James A.
    Beschta, Robert L.
    Wilmers, Christopher C.
    Ritchie, Euan G.
    Hebblewhite, Mark
    Berger, Joel
    Elmhagen, Bodil
    Stockholm University, Faculty of Science, Department of Zoology.
    Letnic, Mike
    Nelson, Michael P.
    Schmitz, Oswald J.
    Smith, Douglas W.
    Wallach, Arian D.
    Wirsing, Aaron J.
    Status and Ecological Effects of the World's Largest Carnivores2014In: Science, ISSN 0036-8075, E-ISSN 1095-9203, Vol. 343, no 6167, p. 151-+Article, review/survey (Refereed)
    Abstract [en]

    Large carnivores face serious threats and are experiencing massive declines in their populations and geographic ranges around the world. We highlight how these threats have affected the conservation status and ecological functioning of the 31 largest mammalian carnivores on Earth. Consistent with theory, empirical studies increasingly show that large carnivores have substantial effects on the structure and function of diverse ecosystems. Significant cascading trophic interactions, mediated by their prey or sympatric mesopredators, arise when some of these carnivores are extirpated from or repatriated to ecosystems. Unexpected effects of trophic cascades on various taxa and processes include changes to bird, mammal, invertebrate, and herpetofauna abundance or richness; subsidies to scavengers; altered disease dynamics; carbon sequestration; modified stream morphology; and crop damage. Promoting tolerance and coexistence with large carnivores is a crucial societal challenge that will ultimately determine the fate of Earth's largest carnivores and all that depends upon them, including humans.

  • 37. Ritchie, Euan G.
    et al.
    Elmhagen, Bodil
    Stockholm University, Faculty of Science, Department of Zoology.
    Glen, Alistair S.
    Letnic, Mike
    Ludwig, Gilbert
    McDonald, Robbie A.
    Ecosystem restoration with teeth: what role for predators?2012In: Trends in Ecology & Evolution, ISSN 0169-5347, E-ISSN 1872-8383, Vol. 27, no 5, p. 265-271Article in journal (Refereed)
    Abstract [en]

    Recent advances highlight the potential for predators to restore ecosystems and confer resilience against globally threatening processes, including climate change and biological invasions. However, releasing the ecological benefits of predators entails significant challenges. Here, we discuss the economic, environmental and social considerations affecting predator-driven ecological restoration programmes, and suggest approaches for reducing the undesirable impacts of predators. Because the roles of predators are context dependent, we argue for increased emphasis on predator functionality in ecosystems and less on the identities and origins of species and genotypes. We emphasise that insufficient attention is currently given to the importance of variation in the social structures and behaviours of predators in influencing the dynamics of trophic interactions. Lastly, we outline experiments specifically designed to clarify the ecological roles of predators and their potential utility in ecosystem restoration.

  • 38.
    Shirley, Mark
    et al.
    Newcastle University.
    Elmhagen, Bodil
    Stockholm University, Faculty of Science, Department of Zoology, Animal Ecology.
    Lurz, Peter
    Newcastle University.
    Rushton, Steve
    Newcastle University.
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology, Animal Ecology.
    Modelling the spatial population dynamics of arctic foxes: the effects of red foxes and microtine cycles2009In: Canadian Journal of Zoology, ISSN 0008-4301, E-ISSN 1480-3283, Vol. 87, p. 1170-1183Article in journal (Refereed)
    Abstract [en]

    The Fennoscandian arctic fox Vulpes lagopus (L., 1758) population is critically endangered, possibly because of increased interference competition from red foxes Vulpes vulpes (L., 1758) and fading cycles in microtine rodents, which cause food shortage. It is not known how these factors drive arctic fox population trends. To test their role in arctic fox decline, we developed a spatially-explicit and individual-based model that allowed us to simulate fox interactions and food availability in a real landscape. A sensitivity analysis revealed that simulated arctic fox population size and den occupancy were strongly correlated with fecundity and mortality during the microtine crash phase, but also with red fox status. Model simulations suggested that arctic fox population trends depended on microtine cycles and that arctic fox distributions were restricted by red fox presence. We compared the model predictions with field data collected at Vindelfjällen, Sweden. The model recreated the observed arctic fox trend only with the inclusion of arctic fox avoidance of red fox home ranges. The results indicate that avoidance behaviours can affect population trends and hence, that relatively small numbers of red foxes can have a strong negative impact on arctic fox population size and distribution.

  • 39.
    Stoessel, Marianne
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Elmhagen, Bodil
    Stockholm University, Faculty of Science, Department of Zoology.
    Vinka, Mikael
    Hellström, Peter
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    The fluctuating world of a tundra predator guild: bottom‐up constraints overrule top‐down species interactions in winter2019In: Ecography, ISSN 0906-7590, E-ISSN 1600-0587, Vol. 42, no 3, p. 488-499Article in journal (Refereed)
    Abstract [en]

    Global warming is predicted to change ecosystem functioning and structure in Arctic ecosystems by strengthening top‐down species interactions, i.e. predation pressure on small herbivores and interference between predators. Yet, previous research is biased towards the summer season. Due to greater abiotic constraints, Arctic ecosystem characteristics might be more pronounced in winter. Here we test the hypothesis that top‐down species interactions prevail over bottom‐up effects in Scandinavian mountain tundra (Northern Sweden) where effects of climate warming have been observed and top‐down interactions are expected to strengthen. But we test this ‘a priori’ hypothesis in winter and throughout the 3–4 yr rodent cycle, which imposes additional pulsed resource constraints. We used snowtracking data recorded in 12 winters (2004–2015) to analyse the spatial patterns of a tundra predator guild (arctic fox Vulpes lagopus, red fox Vulpes vulpes, wolverine Gulo gulo) and small prey (ptarmigan, Lagopus spp). The a priori top‐down hypothesis was then tested through structural equation modelling, for each phase of the rodent cycle. There was weak support for this hypothesis, with top‐down effects only discerned on arctic fox (weakly, by wolverine) and ptarmigan (by arctic fox) at intermediate and high rodent availability respectively. Overall, bottom‐up constraints appeared more influential on the winter community structure. Cold specialist predators (arctic fox and wolverine) showed variable landscape associations, while the boreal predator (red fox) appeared strongly dependent on productive habitats and ptarmigan abundance. Thus, we suggest that the unpredictability of food resources determines the winter ecology of the cold specialist predators, while the boreal predator relies on resource‐rich habitats. The constraints imposed by winters and temporary resource lows should therefore counteract productivity‐driven ecosystem change and have a stabilising effect on community structure. Hence, the interplay between summer and winter conditions should determine the rate of Arctic ecosystem change in the context of global warming.

  • 40.
    Tannerfeldt, Magnus
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Elmhagen, Bodil
    Stockholm University, Faculty of Science, Department of Zoology.
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    Exclusion by interference competition? The relationship between red and arctic foxes2002In: Oecologia, ISSN 0029-8549, E-ISSN 1432-1939, Vol. 132, no 2, p. 213-220Article in journal (Refereed)
    Abstract [en]

    The distribution of many predators may be limited by interactions with larger predator species. The arctic fox in mainland Europe is endangered, while the red fox is increasing its range in the north. It has been suggested that the southern distribution limit of the arctic fox is determined by interspecific competition with the red fox. This has been criticised, on the basis that the species co-exist on a regional scale. However, if the larger red fox is superior and interspecific competition important, the arctic fox should avoid close contact, especially during the breeding season. Consequently, the distribution of breeding dens for the two species would be segregated on a much smaller spatial and temporal scale, in areas where they are sympatric. We tested this hypothesis by analysing den use of reproducing arctic and red foxes over 9 years in Sweden. High quality dens were inhabited by reproducing arctic foxes more often when no red foxes bred in the vicinity. Furthermore, in two out of three cases when arctic foxes did reproduce near red foxes, juveniles were killed by red foxes. We also found that breeding arctic foxes occupied dens at higher altitudes than red foxes did. in a large-scale field experiment, red foxes were removed, but the results were not conclusive. However, we conclude that on the scale of individual territories, arctic foxes avoid areas with red foxes. Through interspecific interference competition, the red fox might thus be excluding the arctic fox from breeding in low altitude habitat, which is most important in years when food abundance is limited and competition is most fierce. With high altitude refuges being less suitable, even small-scale behavioural effects could scale up to significant effects at the population level.

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