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  • 101.
    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.

  • 102.
    Lidén, Kerstin
    et al.
    Stockholm University, Faculty of Humanities, Department of Archaeology and Classical Studies. Stockholm University, Faculty of Humanities, Department of Archaeology and Classical Studies, Archaeological Research Laboratory. Stockholm University, Faculty of Humanities, Centre for the Study of Cultural Evolution.
    Angerbjörn, A.
    Stockholm University, Faculty of Science, Department of Zoology.
    Dietary change and stable isotopes: a model of growth and dormancy in cave bears1999In: Proceedings of the Royal Society of London Series B-Biological Sciences, Vol. 266, no 1430, p. 1779-1783Article in journal (Refereed)
    Abstract [en]

    In order to discuss dietary change over time by the use of stable isotopes, it is necessary to sort out the underlying processes in isotopic variation. Together with the dietary signal other processes have been investigated, namely metabolic processes, collagen turnover and physical growth. However, growth and collagen turnover time have so far been neglected in dietary reconstruction based on stable isotopes. An earlier study suggested that cave bears (Ursus spelaeus) probably gave birth to cubs during dormancy. We provide an estimate of the effect on stable isotopes of growth and metabolism and discuss collagen turnover in a population of cave bears. Based on a quantitative model, we hypothesized that bear cubs lactated their mothers during their first and second winters, but were fed solid food together with lactation during their first summer. This demonstrates the need to include physical growth, metabolism and collagen turnover in dietary reconstruction. Whereas the effects of diet and metabolism are due to fractionation, growth and collagen turnover are dilution processes.

  • 103.
    Lilja Öqvist, Elin
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Granquist, Sandra M.
    Burns, Georgette Leah
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    Seal watching: An investigation of codes of conduct2018In: Tourism in Marine Environments, ISSN 1544-273X, E-ISSN 2169-0197, Vol. 13, no 1, p. 1-15Article in journal (Refereed)
    Abstract [en]

    Seal watching as a form of wildlife tourism is becoming increasingly popular worldwide. Behavioral changes caused by the presence of tourists could lead to negative consequences for seal welfare and may affect reproduction and survival. Therefore, managing seal-watching activities to ensure future protection and conservation is important. Codes of conduct or guidelines for how to behave around animals are one way to regulate wildlife watching and are often easier and quicker to implement than laws. Codes explaining the consequences for wildlife if the code is not followed appeal to the moral obligation of tourists and thereby increase incentives to act appropriately. This study focused on analyzing the content of codes of conduct for seal watching. Codes of conduct (n = 33) accessible on the internet during the time of study were analyzed. Results show that in many areas where seal watching occurs there are no regulations or guidelines. The content and detail of the codes varied and the information was often insufficient to offer adequate protection of seals. Few of the codes were developed in cooperation with scientists or stated that the content was based on research. Further, a majority of the codes did not explain the consequences for wildlife if the code was not followed. More research on seals and the tourists watching them is needed to better understand the effects of tourism and how disturbance could be minimized. Meanwhile, developing an international code of conduct (with local additions) built on existing knowledge in the field could be one option to increase protection and ensure conservation of these animals. The results presented in this article could assist the development of such a code of conduct.

  • 104.
    Lindenfors, Patrik
    et al.
    Stockholm University, Faculty of Science, Department of Zoology, Animal Ecology.
    Dalén, Love
    Stockholm University, Faculty of Science, Department of Zoology, Animal Ecology.
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology, Animal Ecology.
    A monophyletic origin of delayed implantation and its implications2003In: Evolution, ISSN 0014-3820, E-ISSN 1558-5646, Vol. 57, p. 1952-1956Article in journal (Refereed)
  • 105.
    Lotsander, Anna
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Hasselgren, Malin
    Stockholm University, Faculty of Science, Department of Zoology.
    Larm, Malin
    Stockholm University, Faculty of Science, Department of Zoology.
    Wallén, Johan
    Stockholm University, Faculty of Science, Department of Zoology.
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    Norén, Karin
    Stockholm University, Faculty of Science, Department of Zoology.
    Low persistence of genetic rescue across generations in the Arctic fox (Vulpes lagopus)2021In: Journal of Heredity, ISSN 0022-1503, E-ISSN 1465-7333, Vol. 112, no 3, p. 276-285Article in journal (Refereed)
    Abstract [en]

    Genetic rescue can facilitate the recovery of small and isolated populations suffering from inbreeding depression. Long-term effects are however complex and examples spanning over multiple generations under natural conditions are scarce. The aim of this study was to test for long-term effects of natural genetic rescue in a small population of Scandinavian Arctic foxes (Vulpes lagopus). By combining a genetically verified pedigree covering almost 20 years with a long-term dataset on individual fitness (n=837 individuals), we found no evidence for elevated fitness in immigrant F2 and F3 compared to native inbred foxes. Population inbreeding levels showed a fluctuating increasing trend and emergence of inbreeding within immigrant lineages shortly after immigration. Between 0-5 and 6-9 years post immigration, the average population size decreased by almost 22 % and the average proportion of immigrant ancestry rose from 14 % to 27 %. Y chromosome analysis revealed that two out of three native male lineages were lost from the gene pool, but all founders represented at the time of immigration were still contributing to the population at the end of the study period through female descendants. The results highlight the complexity of genetic rescue and suggest that beneficial effects can be brief. Continuous gene flow may be needed for small and threatened populations to recover and persist in a longer time perspective.

  • 106. Machín, Paula
    et al.
    Fernández-Elipe, Juan
    Hungar, Johannes
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    Klaassen, Raymond H. G.
    Aguirre, José
    The role of ecological and environmental conditions on the nesting success of waders in sub-Arctic Sweden2019In: Polar Biology, ISSN 0722-4060, E-ISSN 1432-2056, Vol. 42, no 8, p. 1571-1579Article in journal (Refereed)
    Abstract [en]

    Waders that breed in the sub-Arctic are one of the groups most threatened by climate change. At the same time, wader breeding success also can vary as a function of fluctuations in the numbers of predators and rodents (an alternative prey for the predators). How climate change could influence these foodweb interactions remains poorly studied. In this study, we analysed the effects of ecological (e.g. vole/lemming and predator abundance) and environmental factors (e.g. snow cover) on the breeding success of waders in sub-Arctic Lapland. We monitored more than 500 wader nests during six breeding seasons, which spanned a full rodent cycle and one year of exceptionally late snow melt. Nest predation rate, and thus wader breeding success, did not vary as a function of predator or rodent abundance. However, predation rate was exceptionally high in the year with a late snow melt. More variability in climate is expected for the future, where more precipitation and cold spring temperatures resulting in late snow melt will be more frequent, influencing the rodent and predator numbers, and therefore wader breeding success in the sub-Arctic. Snow would limit the number of open areas for nesting and hence predators would then be able to find these nests more easily. Additionally, predators might concentrate their efforts on alternative prey if snow has reduced their capacity to find other food sources. And, ultimately, changes in the rodent fluctuations could affect the final outcome of predators.

  • 107.
    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)
  • 108.
    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.

  • 109.
    Meijer, Tomas
    et al.
    Stockholm University, Faculty of Science, Department of Zoology, Animal Ecology.
    Mattsson, Roland
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology, Animal Ecology.
    Osterman-Lind, Eva
    Fernandez-Aguilar, Xavier
    Gavier-Widen, Dolores
    Endoparasites in the endangered Fennoscandian population of arctic foxes (Vulpes lagopus)2011In: European Journal of Wildlife Research, ISSN 1612-4642, E-ISSN 1439-0574, Vol. 57, no 4, p. 923-927Article in journal (Refereed)
    Abstract [en]

    The Fennoscandian arctic fox (Vulpes lagopus) population is endangered due to overharvest and competition with the larger red fox (Vulpes vulpes). In this study, we have screened the population in Sweden for endoparasites by analysis of non-invasively faecal samples collected at reproductive dens during two summers, one with low food abundance (2008) and the other with high food abundance (2010). Eggs, larvae and oocysts of a total of 14 different endoparasites were identified with a species richness per inhabited den of 3.2 (CI95% +/- 0.48) in 2008 and 2.7 (CI95% +/- 0.72) in 2010. Capillariidae-like eggs was identified at 59% of the dens in 2008 and 57% in 2010 and Toxocara canis with 7% (2008) and 30% (2010); Toxascaris leonina with 93% (2008) and 65% (2010); Uncinaria stenocephala 65% (2008) and 39% (2010); Crenosoma vulpis 3% (2008) and 4% (2010); Trichuris sp. 7% (2008) and 4% (2010); Cystoisospora canis-like oocysts 28% (2008) and 26% (2010); Cystoisospora ohiensis-like oocysts 38% (2008) and 4% (2010); Eimeria sp. 7% (2008) and 9% (2010); Sarcocystis sp. 3% (2008) and 9% (2010); Taenia sp. 10% (2008) and 4% (2010); Mesocestoides sp. 3% (2008) and 0% (2010); Balantidium sp. 0% (2008) and 9% (2010) and Spiruroidea-like eggs 0% (2008) and 4% (2010). To our knowledge, Balantidium sp., Sarcocystis sp. and Trichuris sp. has never been described before in wild arctic foxes.

  • 110.
    Meijer, Tomas
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Norén, Karin
    Stockholm University, Faculty of Science, Department of Zoology.
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    The impact of maternal experience on post-weaning survival in an endangered arctic fox population2011In: European Journal of Wildlife Research, ISSN 1612-4642, E-ISSN 1439-0574, Vol. 57, no 3, p. 549-553Article in journal (Refereed)
    Abstract [en]

    Behavioural differences in parental care can influence offspring survival through variation in e.g. antipredator behaviour and ability to provide food. In a broad range of species, offspring survival has been found to be higher for experienced females compared to inexperienced first-time breeders. The increase in offspring survival for experienced females has mainly been explained by improved experience in providing food. In this paper, we have studied post-weaning juvenile survival in relation to maternal experience in an endangered population of arctic foxes (Vulpes lagopus) in Fennoscandia. For cubs raised by inexperienced and experienced females, the survival rate was 0.42 (CI 95% +/- 0.31) and 0.87 (CI 95% +/- 0.08), respectively. There was no difference in body condition between the cubs and no observations of starvation. We suggest that the difference in survival was due to lack of experience to one of the most common predators, the golden eagle (Aquila chrysaetos). Golden eagles were mainly observed on dens with litters where the females were inexperienced first-time breeders. From a conservation perspective, it is therefore important to increase adult survival through actions to enlarge the proportion of experienced breeders.

  • 111.
    Meijer, Tomas
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Norén, Karin
    Stockholm University, Faculty of Science, Department of Zoology.
    Hellström, Peter
    Stockholm University, Faculty of Science, Department of Zoology.
    Dalén, Love
    Stockholm University, Faculty of Science, Department of Zoology.
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    Estimating population parameters in a threatened arctic fox population using molecular tracking and traditional field methods2008In: Animal Conservation, ISSN 1469-1795, Vol. 11, no 4, p. 330-338Article in journal (Refereed)
    Abstract [en]

    Comprehensive population parameter data are useful for assessing effective conservation actions. The Fennoscandian arctic fox Alopex lagopus is critically endangered and the population size is estimated at 120 individuals that are fragmented into four isolated populations. Here, we use molecular tracking and visual observations to estimate population size and survival in one of the populations on the Swedish mountain tundra during a year of low food availability. We collected 98 arctic fox faecal samples during the winter of 2006 and recorded visual observations of ear-tagged individuals during the summer of 2005 and 2006. The faecal samples were analysed for variation in nine microsatellite loci and matched to the genetic profiles of previously ear-tagged individuals from 2001 to 2005. During winter 2006, the minimum number alive was 12 individuals using visual observations, 30 using molecular tracking and 36 by combining the datasets. Population size was estimated through mark–recapture for the molecular tracking and visual observation datasets and through rarefaction analyses for molecular tracking data. The mark–recapture estimate for visual observations was uninformative due to the large confidence interval (CI) (i.e. 6–212 individuals). Based on the molecular tracking dataset combined with the minimum number alive for visual observations and molecular tracking, we concluded a consensus population size of 36–55 individuals. We also estimated the age-specific finite survival rate during 1 year (July 2005 to July 2006) by combining molecular tracking with visual observations. Juvenile survival on a yearly basis was 0.08 (95% CI 0.02–0.18) while adults had a survival of 0.59 (95% CI 0.39–0.82). Juveniles displayed a lower survival than the adults during autumn (P<0.01) whereas no age-specific survival difference during spring was found. The risk of negative effects due to the small population size and low juvenile survival is accordingly considerable.

  • 112. Meyer, Nicolas
    et al.
    Bollache, Loic
    Dechaume-Moncharmont, Francois-Xavier
    Moreau, Jerome
    Afonso, Eve
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    Bety, Joel
    Ehrich, Dorothee
    Gilg, Vladimir
    Giroux, Marie-Andree
    Hansen, Jannik
    Lanctot, Richard B.
    Lang, Johannes
    Lecomte, Nicolas
    McKinnon, Laura
    Reneerkens, Jeroen
    Saalfeld, Sarah T.
    Sabard, Brigitte
    Schmidt, Niels M.
    Sittler, Benoit
    Smith, Paul
    Sokolov, Aleksandr
    Sokolov, Vasiliy
    Sokolova, Natalia
    van Bemmelen, Rob
    Gilg, Olivier
    Nest attentiveness drives nest predation in arctic sandpipers2020In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 129, no 10, p. 1481-1492Article in journal (Refereed)
    Abstract [en]

    Most birds incubate their eggs to allow embryo development. This behaviour limits the ability of adults to perform other activities. Hence, incubating adults trade off incubation and nest protection with foraging to meet their own needs. Parents can either cooperate to sustain this tradeoff or incubate alone. The main cause of reproductive failure at this reproductive stage is predation and adults reduce this risk by keeping the nest location secret. Arctic sandpipers are interesting biological models to investigate parental care evolution as they may use several parental care strategies. The three main incubation strategies include both parents sharing incubation duties ('biparental'), one parent incubating alone ('uniparental'), or a flexible strategy with both uniparental and biparental incubation within a population ('mixed'). By monitoring the incubation behaviour in 714 nests of seven sandpiper species across 12 arctic sites, we studied the relationship between incubation strategy and nest predation. First, we described how the frequency of incubation recesses (NR), their mean duration (MDR), and the daily total duration of recesses (TDR) vary among strategies. Then, we examined how the relationship between the daily predation rate and these components of incubation behaviour varies across strategies using two complementary survival analysis. For uniparental and biparental species, the daily predation rate increased with the daily total duration of recesses and with the mean duration of recesses. In contrast, daily predation rate increased with the daily number of recesses for biparental species only. These patterns may be attributed to two independent mechanisms: cryptic incubating adults are more difficult to locate than unattended nests and adults departing the nest or feeding close to the nest can draw predators' attention. Our results demonstrate that incubation behaviour as mediated by incubation strategy has important consequences for sandpipers' reproductive success.

  • 113. Meyer, Nicolas
    et al.
    Bollache, Loïc
    Galipaud, Matthias
    Moreau, Jérôme
    Dechaume-Moncharmont, François-Xavier
    Afonso, Eve
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    Bêty, Joël
    Brown, Glen
    Ehrich, Dorothée
    Gilg, Vladimir
    Giroux, Marie-Andrée
    Hansen, Jannik
    Lanctot, Richard
    Lang, Johannes
    Latty, Christopher
    Lecomte, Nicolas
    McKinnon, Laura
    Kennedy, Lisa
    Reneerkens, Jeroen
    Saalfeld, Sarah
    Sabard, Brigitte
    Schmidt, Niels M.
    Sittler, Benoît
    Smith, Paul
    Sokolov, Aleksander
    Sokolov, Vasiliy
    Sokolova, Natalia
    van Bemmelen, Rob
    Varpe, Øystein
    Gilg, Olivier
    Behavioural responses of breeding arctic sandpipers to ground-surface temperature and primary productivity2021In: Science of the Total Environment, ISSN 0048-9697, E-ISSN 1879-1026, Vol. 755, article id 142485Article in journal (Refereed)
    Abstract [en]

    Most birds incubate their eggs, which requires time and energy at the expense of other activities. Birds generally have two incubation strategies: biparental where both mates cooperate in incubating eggs, and uniparental where a single parent incubates. In harsh and unpredictable environments, incubation is challenging due to high energetic demands and variable resource availability. We studied the relationships between the incubation behaviour of sandpipers (genus Calidris) and two environmental variables: temperature and a proxy of primary productivity (i.e. NDVI). We investigated how these relationships vary between incubation strategies and across species among strategies. We also studied how the relationship between current temperature and incubation behaviour varies with previous day's temperature. We monitored the incubation behaviour of nine sandpiper species using thermologgers at 15 arctic sites between 2016 and 2019. We also used thermologgers to record the ground surface temperature at conspecific nest sites and extracted NDVI values from a remote sensing product. We found no relationship between either environmental variables and biparental incubation behaviour. Conversely, as ground-surface temperature increased, uniparental species decreased total duration of recesses (TDR) and mean duration of recesses (MDR), but increased number of recesses (NR). Moreover, small species showed stronger relationships with ground-surface temperature than large species. When all uniparental species were combined, an increase in NDVI was correlated with higher mean duration, total duration and number of recesses, but relationships varied widely across species. Finally, some uniparental species showed a lag effect with a higher nest attentiveness after a warm day while more recesses occurred after a cold day than was predicted based on current temperatures. We demonstrate the complex interplay between shorebird incubation strategies, incubation behaviour, and environmental conditions. Understanding how species respond to changes in their environment during incubation helps predict their future reproductive success.

  • 114. Moen, Jon
    et al.
    Aune, Karin.
    Edenius, Lars
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    Potential effects of climate change on treeline position in the Swedish mountains2004In: Ecology and Society, E-ISSN 1708-3087, Vol. 9, no 1, p. Article Number 16-Article in journal (Refereed)
    Abstract [en]

    Climate change may strongly influence species distribution and, thus, the structure and function of ecosystems. This paper describes simulated changes in the position of the upper treeline in the Swedish mountains in response to predicted climate change. Data on predicted summer temperature changes, the current position of the treeline, and a digital elevation model were used to predict the position of the treeline over a 100-year timeframe. The results show the treeline advancing upward by 233-667 m, depending on the climate scenario used and location within the mountain chain. Such changes hypothetically caused a 75-85% reduction in treeless alpine heaths, with 60-93% of the remaining areas being scree slopes and boulder fields. For this change to occur, the migration rate of the trees would be in the order of 23-221 m yr(-1), which is well within published migration rates for wind-dispersed deciduous trees. The remaining alpine areas would be strongly fragmented. These drastic changes would influence all aspects of mountain ecosystems, including biodiversity conservation and human land-use patterns.

  • 115.
    Mwandya, Augustine
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Gullström, Martin
    Stockholm University, Faculty of Science, Department of Zoology.
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    Influence of mangrove deforestation on trophic organization of fish assemblages in creek systemsManuscript (Other academic)
    Abstract [en]

    The mangrove biotopes in Tanzania are under increasing pressure from domestic uses and changes in land-use for aquaculture and solar salt farms. To investigate the impacts of man-made activities on trophic structure of mangrove-associated fish species, sampling of fish from various trophic groups was performed in mangrove creeks. Trophic organization and stable isotope signatures (δ 13C and δ 15N) of fish in undisturbed areas of mangrove creeks were compared with clear-cut areas of mangrove as well as with reservoirs for saltworks or fish farms constructed after mangrove clearing. Results showed significantly higher densities, species numbers, diversity (H’) and numbers of trophic groups in undisturbed sites compared to both types of disturbed sites. Overall, omnivorous fish comprised the most abundant feeding guild, with the highest number of individuals found in the cleared sites followed in order by the uncleared sites and the reservoirs. The feeding guild zoobenthivores/piscivores was the most diverse group, with the highest species richness in the undisturbed areas. Multivariate analysis showed that assemblage structure of omnivores in the reservoirs was separated from those in the uncleared and cleared sites, while zoobenthivores/piscivores differed between uncleared sites and the disturbed areas (cleared sites and reservoirs). Stable isotope ratios of δ13C and δ15N values in fish tissue muscles indicate significant diet shifts between undisturbed and disturbed mangrove creek systems, although the effects are species-specific. Our findings suggest that mangrove deforestation combined with land-use changes, such as salt- or fish farm constructions, has a greater impact on the trophic structure of fish in mangrove creeks than mangrove deforestation only. Hence, the extent and severity of disturbance seem to be important in predicting fish assemblage composition.

  • 116.
    Naud, Lucy
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Måsviken, Johannes
    Stockholm University, Faculty of Science, Department of Zoology.
    Freire, Susana
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    Dalén, Love
    Stockholm University, Faculty of Science, Department of Zoology. Swedish Museum of Natural History, Sweden.
    Dalerum, Fredrik
    Stockholm University, Faculty of Science, Department of Zoology. Oviedo University, Spain; University of Pretoria, South Africa.
    Altitude effects on spatial components of vascular plant diversity in a subarctic mountain tundra2019In: Ecology and Evolution, E-ISSN 2045-7758, Vol. 9, no 8, p. 4783-4795Article in journal (Refereed)
    Abstract [en]

    Environmental gradients are caused by gradual changes in abiotic factors, which affect species abundances and distributions, and are important for the spatial distribution of biodiversity. One prominent environmental gradient is the altitude gradient. Understanding ecological processes associated with altitude gradients may help us to understand the possible effects climate change could have on species communities. We quantified vegetation cover, species richness, species evenness, beta diversity, and spatial patterns of community structure of vascular plants along altitude gradients in a subarctic mountain tundra in northern Sweden. Vascular plant cover and plant species richness showed unimodal relationships with altitude. However, species evenness did not change with altitude, suggesting that no individual species became dominant when species richness declined. Beta diversity also showed a unimodal relationship with altitude, but only for an intermediate spatial scale of 1km. A lack of relationships with altitude for either patch or landscape scales suggests that any altitude effects on plant spatial heterogeneity occurred on scales larger than individual patches but were not effective across the whole landscape. We observed both nested and modular patterns of community structures, but only the modular patterns corresponded with altitude. Our observations point to biotic regulations of plant communities at high altitudes, but we found both scale dependencies and inconsistent magnitude of the effects of altitude on different diversity components. We urge for further studies evaluating how different factors influence plant communities in high altitude and high latitude environments, as well as studies identifying scale and context dependencies in any such influences.

  • 117. Nelson, D. E.
    et al.
    Angerbjörn, A.
    Stockholm University, Faculty of Science, Department of Zoology.
    Liden, K.
    Stockholm University, Faculty of Humanities, Department of Archaeology and Classical Studies. Stockholm University, Faculty of Humanities, Department of Archaeology and Classical Studies, Archaeological Research Laboratory. Stockholm University, Faculty of Humanities, Centre for the Study of Cultural Evolution.
    Turk, I.
    Stable isotopes and the metabolism of the European cave bear1998In: Oecologia, Vol. 116, no 1-2, p. 177-181Article in journal (Refereed)
    Abstract [en]

    Isotopic analyses of fossil bones of the extinct European cave bear indicate that this animal was a hibernator with the same unusual metabolic processes as some modern bear species. This finding provides useful biological and archaeological information on an extinct species, and the methods themselves may prove generally useful in studies of the metabolisms of modern bears, other hibernators, and perhaps of starving animals.

  • 118.
    Norén, Karin
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    Genetic perspectives on northern population cycles: bridging the gap between theory and empirical studies2014In: Biological Reviews, ISSN 1464-7931, E-ISSN 1469-185X, Vol. 89, no 2, p. 493-510Article, review/survey (Refereed)
    Abstract [en]

    Many key species in northern ecosystems are characterised by high-amplitude cyclic population demography. In 1924,Charles Elton described the ecology and evolution of cyclic populations in a classic paper and, since then, a major focushas been the underlying causes of population cycles. Elton hypothesised that fluctuations reduced population geneticvariation and influenced the direction of selection pressures. In concordance with Elton, present theories concern thedirect consequences of population cycles for genetic structure due to the processes of genetic drift and selection, but alsoinclude feedback models of genetic composition on population dynamics. Most of these theories gained mathematicalsupport during the 1970s and onwards, but due to methodological drawbacks, difficulties in long-term sampling and acomplex interplay between microevolutionary processes, clear empirical data allowing the testing of these predictionsare still scarce. Current genetic tools allow for estimates of genetic variation and identification of adaptive genomicregions, making this an ideal time to revisit this subject. Herein, we attempt to contribute towards a consensus regardingthe enigma described by Elton almost 90 years ago. We present nine predictions covering the direct and genetic feedbackconsequences of population cycles on genetic variation and population structure, and review the empirical evidence.Generally, empirical support for the predictions was low and scattered, with obvious gaps in the understanding of basicpopulation processes. We conclude that genetic variation in northern cyclic populations generally is high and that thegeographic distribution and amount of diversity are usually suggested to be determined by various forms of context-and density-dependent dispersal exceeding the impact of genetic drift. Furthermore, we found few clear signaturesof selection determining genetic composition in cyclic populations. Dispersal is assumed to have a strong impact ongenetic structuring and we suggest that the signatures of other microevolutionary processes such as genetic drift andselection are weaker and have been over-shadowed by density-dependent dispersal. We emphasise that basic biologicaland demographical questions still need to be answered and stress the importance of extensive sampling, appropriatechoice of tools and the value of standardised protocols.

  • 119. Norén, Karin
    et al.
    Angerbjörn, Anders
    Ännu ett hot mot skandinaviska fjällrävar – gener från pälsfarmer2007In: Våra Rovdjur, Vol. 1, p. 8-9Article in journal (Other (popular science, discussion, etc.))
  • 120.
    Norén, Karin
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    Hersteinsson, Páll
    Population structure in an isolated Arctic fox, Vulpes lagopus, population: the impact of geographical barriers2009In: Biological Journal of the Linnean Society, ISSN 0024-4066, E-ISSN 1095-8312, Vol. 97, no 1, p. 18-26Article in journal (Refereed)
    Abstract [en]

    The genetic composition of a population reflects several aspects of the organism and its environment. The Icelandic Arctic fox population exceeds 8000 individuals and is comprised of both coastal and inland foxes. Several factors may affect within-population movement and subsequent genetic population structure. A narrow isthmus and sheep-proof fences may prevent movement between the north-western and central part and glacial rivers may reduce movement between the eastern and central part of Iceland. Moreover, population density and habitat characteristics can influence movement behaviour further. Here, we investigate the genetic structure in the Icelandic Arctic fox population (n = 108) using 10 microsatellite loci. Despite large glacial rivers, we found low divergence between the central and eastern part, suggesting extensive movement between these areas. However, both model- and frequency-based analyses suggest that the north-western part is genetically differentiated from the rest of Iceland (F-ST = 0.04, D-S = 0.094), corresponding to 100-200 generations of complete isolation. This suggests that the fences cannot be the sole cause of divergence. Rather, the isthmus causes limited movement between the regions, implying that protection in the Hornstrandir Nature Reserve has a minimal impact on Arctic fox population size in the rest of Iceland. (C) 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 97, 18-26.

  • 121.
    Norén, Karin
    et al.
    Stockholm University, Faculty of Science, Department of Zoology. University of California Davis, USA.
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    Wallén, Johan
    Stockholm University, Faculty of Science, Department of Zoology.
    Meijer, Tomas
    Stockholm University, Faculty of Science, Department of Zoology. National Veterinary Institute, Sweden.
    Sacks, Benjamin N.
    Red foxes colonizing the tundra: genetic analysis as a tool for population management2017In: Conservation Genetics, ISSN 1566-0621, E-ISSN 1572-9737, Vol. 18, no 2, p. 359-370Article in journal (Refereed)
    Abstract [en]

    Climate change accelerates biodiversity alterations in northern ecosystems. A prevalent example is that tundra regions are invaded by boreal species. This impacts negatively on native species through competition, predation and transmission of zoonoses. Scandinavian red foxes (Vulpes vulpes) have emerged into the tundra and have altered the structure and function of the tundra community. For instance, they threaten persistence of the endangered Swedish Arctic fox (Vulpes lagopus). County board administrations implement control of the tundra red foxes, but little is known about the underlying expansion dynamics. A broad-scale study revealed high connectivity where northern areas were supplemented with red foxes from surrounding population. However, red fox expansion is most prevalent in tundra regions and the fine-scaled expansion dynamics in these areas have not yet been disseminated. With the aim of identifying the invasive pathways of tundra red foxes, we present microsatellite data for 205 Swedish red foxes and mitochondrial sequence variation in 102 foxes sampled across the historical boreo-nemoral distribution and recently colonized tundra regions. Genetic structuring was low with high levels of ongoing, asymmetric dispersal from surrounding boreal zones into tundra habitats causing high genetic admixture. In both tundra and boreo-nemoral regions, inter-individual relatedness decreased with increasing geographic distance and data suggests male-biased dispersal patterns. Overall, fine-scaled expansion patterns were affected by multiple factors and we discuss its implications for future red fox management.

  • 122.
    Norén, Karin
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Carmichael, Lindsey
    Dalén, Love
    Stockholm University, Faculty of Science, Department of Zoology.
    Hersteinsson, Páll
    Samelius, Gustaf
    Fuglei, Eva
    Kapel, Christian M. O.
    Menyushina, Irina
    Strobeck, Curtis
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    Arctic fox Vulpes lagopus population structure: circumpolar patterns and processes2011In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 120, no 6, p. 873-885Article in journal (Refereed)
    Abstract [en]

    Movement is a prominent process shaping genetic population structure. In many northern mammal species, population structure is formed by geographic distance, geographical barriers and various ecological factors that influence movement over the landscape. The Arctic fox Vulpes lagopus is a highly mobile, opportunistic carnivore of the Arctic that occurs in two main ecotypes with different ecological adaptations. We assembled microsatellite data in 7 loci for 1834 Arctic foxes sampled across their entire distribution to describe the circumpolar population structure and test the impact of (1) geographic distance, (2) geographical barriers and (3) ecotype designation on the population structure. Both Structure and Geneland demonstrated distinctiveness of Iceland and Scandinavia whereas low differentiation was observed between North America-northern Greenland, Svalbard and Siberia. Genetic differentiation was significantly correlated to presence of sea ice on a global scale, but not to geographical distance or ecotype designation. However, among areas connected by sea ice, we recorded a pattern of isolation by distance. The maximum likelihood approach in Migrate suggested that connectivity across North America-northern Greenland and Svalbard was particularly high. Our results demonstrate the importance of sea ice for maintaining connectivity between Arctic fox populations and we therefore predict that climate change will increase genetic divergence among populations in the future.

  • 123.
    Norén, Karin
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Carmichael, Lindsey
    Fuglei, Eva
    Eide, Nina E.
    Hersteinsson, Páll
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    Pulses of movement cause temporal genetic shifts in the High ArcticManuscript (preprint) (Other academic)
  • 124.
    Norén, Karin
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Carmichael, Lindsey
    Fuglei, Eva
    Eide, Nina
    Hersteinsson, Pall
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    Pulses of movement across the sea ice: population connectivity and temporal genetic structure in the arctic fox2011In: Oecologia, ISSN 0029-8549, E-ISSN 1432-1939, Vol. 166, no 4, p. 973-984Article in journal (Refereed)
    Abstract [en]

    Lemmings are involved in several important functions in the Arctic ecosystem. The Arctic fox (Vulpes lagopus) can be divided into two discrete ecotypes: “lemming foxes” and “coastal foxes”. Crashes in lemming abundance can result in pulses of “lemming fox” movement across the Arctic sea ice and immigration into coastal habitats in search for food. These pulses can influence the genetic structure of the receiving population. We have tested the impact of immigration on the genetic structure of the “coastal fox” population in Svalbard by recording microsatellite variation in seven loci for 162 Arctic foxes sampled during the summer and winter over a 5-year period. Genetic heterogeneity and temporal genetic shifts, as inferred by STRUCTURE simulations and deviations from Hardy–Weinberg proportions, respectively, were recorded. Maximum likelihood estimates of movement as well as STRUCTURE simulations suggested that both immigration and genetic mixture are higher in Svalbard than in the neighbouring “lemming fox” populations. The STRUCTURE simulations and AMOVA revealed there are differences in genetic composition of the population between summer and winter seasons, indicating that immigrants are not present in the reproductive portion of the Svalbard population. Based on these results, we conclude that Arctic fox population structure varies with time and is influenced by immigration from neighbouring populations. The lemming cycle is likely an important factor shaping Arctic fox movement across sea ice and the subsequent population genetic structure, but is also likely to influence local adaptation to the coastal habitat and the prevalence of diseases.

  • 125.
    Norén, Karin
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Dalén, Love
    Stockholm University, Faculty of Science, Department of Zoology. Swedish Museum of Natural History, Sweden.
    Flagstad, Øystein
    Berteaux, Dominique
    Wallén, Johan
    Stockholm University, Faculty of Science, Department of Zoology.
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    Evolution, ecology and conservation—revisiting three decades of Arctic fox population genetic research2017In: Polar Research, ISSN 0800-0395, E-ISSN 1751-8369, Vol. 36, article id 4Article, review/survey (Refereed)
    Abstract [en]

    Three decades have passed since the Arctic fox (Vulpes lagopus) was first put into a population genetic perspective. With the aim of addressing how microevolution operates on different biological levels, we here review genetic processes in the Arctic fox at the level of species, populations and individuals. Historical and present dispersal patterns, especially in the presence of sea ice, are the most powerful factors that create a highly homogeneous genetic structure across the circumpolar distribution, with low detectable divergence between the coastal and lemming ecotypes. With dispersal less pronounced or absent, other processes emerge; populations that are currently isolated, for example, because of the lack of sea ice, are genetically divergent. Moreover, small populations generally display signatures of genetic drift, inbreeding, inbreeding depression and, under specific situations, hybridization with domestic fox breeds. Mating system and social organization in the Arctic fox appear to be determined by the ecological context, with complex mating patterns and social groups being more common under resource-rich conditions. In isolated populations, complex social groups and inbreeding avoidance have been documented. We emphasize the value of genetic data to decipher many previously unknown aspects of Arctic fox biology, while these data also raise numerous questions that remain unanswered. Pronounced intra-specific ecological variation makes the Arctic fox an ideal study organism for population genetic processes and the emergence of functional genomics will generate an even deeper understanding of evolution, ecology and conservation issues for several species.

  • 126.
    Norén, Karin
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Dalén, Love
    Stockholm University, Faculty of Science, Department of Zoology.
    Kvaloy, Kirsti
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    Detection of farm fox and hybrid genotypes among wild arctic foxes in Scandinavia2005In: Conservation Genetics, Vol. 6, p. 885-894Article in journal (Refereed)
  • 127.
    Norén, Karin
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Godoy, Erika
    Stockholm University, Faculty of Science, Department of Zoology.
    Dalén, Love
    Stockholm University, Faculty of Science, Department of Zoology. Swedish Museum of Natural History, Sweden.
    Meijer, Tomas
    Stockholm University, Faculty of Science, Department of Zoology. National Veterinary Institute, Sweden.
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    Inbreeding depression in a critically endangered carnivore2016In: Molecular Ecology, ISSN 0962-1083, E-ISSN 1365-294X, Vol. 25, no 14, p. 3309-3318Article in journal (Refereed)
    Abstract [en]

    Harmful effects arising from matings between relatives (inbreeding) is a long-standing observation that is well founded in theory. Empirical evidence for inbreeding depression in natural populations is however rare because of the challenges of assembling pedigrees supplemented with fitness traits. We examined the occurrence of inbreeding and subsequent inbreeding depression using a unique data set containing a genetically verified pedigree with individual fitness traits for a critically endangered arctic fox (Vulpes lagopus) population. The study covered nine years and was comprised of 33 litters with a total of 205 individuals. We recorded that the present population was founded by only five individuals. Over the study period, the population exhibited a tenfold increase in average inbreeding coefficient with a final level corresponding to half-sib matings. Inbreeding mainly occurred between cousins, but we also observed two cases of full-sib matings. The pedigree data demonstrated clear evidence of inbreeding depression on traditional fitness traits where inbred individuals displayed reduced survival and reproduction. Fitness traits were however differently affected by the fluctuating resource abundande. Inbred individuals born at low-quality years displayed reduced first-year survival, while inbred individuals born at high-quality years were less likely to reproduce. The documentation of inbreeding depression in fundamental fitness traits suggests that inbreeding depression can limit population recovery. Introducing new genetic material to promote a genetic rescue effect may thus be necessary for population long-term persistence.

  • 128.
    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.

  • 129.
    Norén, Karin
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Hersteinsson, Páll
    Samelius, Gustaf
    Eide, Nina E.
    Fuglei, Eva
    Elmhagen, Bodil
    Dalén, Love
    Stockholm University, Faculty of Science, Department of Zoology.
    Meijer, Tomas
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    From monogamy to complexity: Arctic fox social organizationManuscript (preprint) (Other academic)
  • 130.
    Norén, Karin
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Kvaloy, Kirsti
    Nyström, Veronica
    Stockholm University, Faculty of Science, Department of Zoology.
    Landa, Arild
    Dalén, Love
    Stockholm University, Faculty of Science, Department of Zoology.
    Eide, Nina E.
    Ostbye, Eivind
    Henttonen, Heikki
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    Farmed arctic foxes on the Fennoscandian mountain tundra: implications for conservation2009In: Animal Conservation, ISSN 1367-9430, E-ISSN 1469-1795, Vol. 12, no 5, p. 434-444Article in journal (Refereed)
    Abstract [en]

    Hybridization between wild and captive-bred individuals is a serious conservation issue that requires measures to prevent negative effects. Such measures are, however, often considered controversial by the public, especially when concerning charismatic species. One of the threats to the critically endangered Fennoscandian arctic fox Alopex lagopus is hybridization with escaped farm foxes, conveying a risk of outbreeding depression through loss of local adaptations to the lemming cycle. In this study, we investigate the existence of escaped farm foxes among wild arctic foxes and whether hybridization has occurred in the wild. We analysed mitochondrial control region sequences and 10 microsatellite loci in samples from free-ranging foxes and compared them with reference samples of known farm foxes and true Fennoscandian arctic foxes. We identified the farm fox specific mitochondrial haplotype H9 in 25 out of 182 samples, 21 of which had been collected within or nearby the wild subpopulation on Hardangervidda in south-western Norway. Genetic analyses of museum specimens collected on Hardangervidda (1897–1975) suggested that farm fox genotypes have recently been introduced to the area. Principal component analysis as well as both model- and frequency-based analyses of microsatellite data imply that the free-ranging H9s were farm foxes rather than wild arctic foxes and that the entire Hardangervidda population consisted of farm foxes or putative hybrids. We strongly recommend removal of farm foxes and hybrids in the wild to prevent genetic pollution of the remaining wild subpopulations of threatened arctic foxes.

  • 131.
    Nyström, Jesper
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Dalén, Love
    Stockholm University, Faculty of Science, Department of Zoology.
    Ekenstedt, Johan
    Angleby, Helen
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    Effect of local prey availability on gyrfalcon diet: DNA analysis on ptarmigan remains at nest sites2006In: Journal of Zoology, ISSN 0952-8369, E-ISSN 1469-7998, Vol. 269, no 1, p. 57-64Article in journal (Refereed)
    Abstract [en]

    The aim of this study was to investigate how the diet of gyrfalcon Falco rusticolus in northern Sweden was affected by the relative availability of its two main prey species: rock ptarmigan Lagopus mutus and willow ptarmigan Lagopus lagopus. In order to do so, we needed a method to estimate the gyrfalcon's diet proportions of rock and willow ptarmigan from prey remains that we collected from nest sites in separate breeding territories. We also needed a method to calculate the availability of the two prey species in the same breeding territories that the prey remains originated from. We could then compare the diet proportions with prey availability and investigate if the gyrfalcons utilized the two species strictly in relation to their densities, or if they showed a preference for any of the prey species. Morphometric identification to species level from ptarmigan remains was not possible. Therefore, we developed a PCR-based process of DNA analysis, which could be applied on any ptarmigan bone or bone remains. This method allowed us to establish the ratio of rock and willow ptarmigan in gyrfalcon diets that originated from single gyrfalcon breeding occasions. The relative availability of the two ptarmigan species in gyrfalcon breeding territories was calculated with a GIS model that incorporated observations on ptarmigan habitat preferences. The DNA identification was performed on 176 ptarmigan bones from 13 different breeding occasions occurring in five different territories. The results indicated that the two ptarmigan species comprised at least 93% of the average gyrfalcon diet, and that rock ptarmigan was the most common prey during all 13 breeding occasions. There was a positive relationship between the relative amount of rock ptarmigan in the diet and the proportion of rock ptarmigan habitat in the territories; hence, the gyrfalcons ptarmigan utilization seemed to be density dependent. However, rock ptarmigan was found to be overrepresented in the diet, which may reflect a preference for rock ptarmigan over willow ptarmigan. The conservation implications of these findings in relation to ptarmigan hunting are discussed.

  • 132.
    Nyström, Jesper
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Ekenstedt, Johan
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    Thulin, Linda
    Stockholm University, Faculty of Science, Department of Zoology.
    Hellström, Peter
    Stockholm University, Faculty of Science, Department of Zoology.
    Dalén, Love
    Stockholm University, Faculty of Science, Department of Zoology.
    Golden Eagles on the Swedish mountain tundra - diet and breeding success in relation to prey fluctuations2006In: Ornis Fennica, ISSN 0030-5685, Vol. 83, no 4, p. 145-152Article in journal (Refereed)
    Abstract [en]

    We studied the diet and the relationship between prey density fluctuations and breeding success of a Golden Eagle (Aquila chrysaetos) population on the mountain tundra region of northern Sweden. We used a new PCR based method to analyse the DNA in bone fragments from Golden Eagle prey remains. This allowed us to accurately identify the Ptarmigan species that the bone fragments originated from, and hence, establish the proportions of Ptarmigan species in the eagle's diet. We could conclude that Ptarmigan species (Lagopus spp.) are the most important prey category for this Golden Eagle population (63% of all identified prey), and that Willow Ptarmigan (L. lagopus) occurred more frequently in the diet than Rock Ptarmigan (L. mutus) did (Willow Ptarmigan 38%, Rock Ptarmigan 25%). Other important prey included reindeer (Rang fer tarandus), mountain hare (Lepus timidus) and microtine rodents. The Golden Eagles managed to maintain a relatively broad food niche, despite an environment with low prey diversity. Microtine rodents, hare and Ptarmigan populations showed similar population fluctuations in the study area. The breeding success of the Golden Eagles showed a strong relationship to the yearly density index of the most important prey category, the Ptarmigan species.

  • 133.
    Nyström, Jesper
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Ekenstedt, Johan
    Engström, Johan
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    Gyr falcons, ptarmigan and microtine rodents in Northern Sweden2005In: Ibis, ISSN 0019-1019, E-ISSN 1474-919X, Vol. 147, no 3, p. 587-597Article in journal (Refereed)
    Abstract [en]

    A Gyr Falcon Falco rusticolus population in Northern Sweden (66°N, 17°E) was monitored from 1996 to 2002 in relation to its predator–prey interactions with its main and alternative prey species. Ptarmigan species Lagopus spp., and especially Rock Ptarmigan L. mutus, were the Gyr Falcons’ most important prey and constituted more than 90% of the prey biomass. A 21-fold difference in ptarmigan abundance was found across Falcon breeding territories. However, this great variation in prey availability corresponded to only about a 10% shift in Gyr Falcon diet across territories, suggesting that the Falcons were reluctant or unable to compensate for declining ptarmigan availability by using alternative prey categories. Gyr Falcons did not respond functionally to microtine rodent abundance. Their diets were unaffected by a peak in the microtine rodent population cycle when Norwegian Lemmings Lemmus lemmus occurred in high numbers in the study area. Gyr Falcons responded numerically to their prey in two ways. First, there was a reproductive response with a significant relationship between the number of chicks fledged and the number of ptarmigan in the breeding territories. Secondly, although the Gyr Falcons did not utilize microtines as prey, there was a relationship between the microtine rodent abundance and the number of pairs that attempted to breed each year. This could be a result of an indirect community interaction, assuming that other predators switched from ptarmigan to microtines as prey, which could have had a positive effect on the breeding performance of the Gyr Falcons. The Gyr Falcons acted as true specialist predators, and their narrow food niche probably reflected a general lack of suitable alternative prey in the study area.

  • 134.
    Nyström, Veronica
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    Dalén, Love
    Stockholm University, Faculty of Science, Department of Zoology.
    Genetic consequences of a demographic bottleneck in the Scandinavian arctic fox2006In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 114, no 1, p. 84-94Article in journal (Refereed)
    Abstract [en]

    Demographic bottlenecks can result in a loss of genetic variation due to the bottleneck effect and subsequent genetic drift. The arctic fox population in Scandinavia went through a severe demographic bottleneck in the early 20th century, and is today classified as critically endangered. In this study, we investigated the pre-bottleneck genetic variation in Scandinavia and compared it to modern samples from Scandinavia and North Russia. Variation in the mtDNA control region and five microsatellite loci was examined through ancient DNA analysis on museum specimens. The microsatellite data from the museum specimens was further used to simulate the expected effect of the bottleneck. The arctic foxes in Scandinavia have lost approximately 25% of the microsatellite alleles and four out of seven mtDNA haplotypes. The results also suggest that the genetic differentiation between North Russia and Scandinavia has doubled over the last 100 years. However, the level of heterozygosity was significantly higher than expected from the simulations. This highlights both the advantage of using museum specimens and the importance of generating specific predictions in conservation genetics.

  • 135.
    Nyström, Veronica
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Dalén, Love
    Stockholm University, Faculty of Science, Department of Zoology.
    Vartanyan, Sergey
    Department of Geography, Herzen University, nab. Moyki, 48, St Petersburg.
    Lidén, Kerstin
    Stockholm University, Faculty of Humanities, Department of Archaeology and Classical Studies.
    Ryman, Nils
    Stockholm University, Faculty of Science, Department of Zoology.
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    Temporal genetic change in the last remaining population of woolly mammoth2010In: Proceedings of the Royal Society of London. Biological Sciences, ISSN 0962-8452, E-ISSN 1471-2954, Vol. 277, no 1692, p. 2331-2337Article in journal (Refereed)
    Abstract [en]

    During the Late Pleistocene, the woolly mammoth (Mammuthus primigenius) experienced a series of local extinctions generally attributed to human predation or environmental change. Some small and isolated populations did however survive far into the Holocene. Here, we investigated the genetic consequences of the isolation of the last remaining mammoth population on Wrangel Island. We analysed 741 bp of the mitochondrial DNA and found a loss of genetic variation in relation to the isolation event, probably caused by a demographic bottleneck or a founder event. However, in spite of ca 5000 years of isolation, we did not detect any further loss of genetic variation. Together with the relatively high number of mitochondrial haplotypes on Wrangel Island near the final disappearance, this suggests a sudden extinction of a rather stable population.

  • 136.
    Nyström, Veronica
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Humphrey, Joanne
    Skoglund, Pontus
    McKeown, Niall J.
    Vartanyan, Sergey
    Shaw, Paul W.
    Lidén, Kerstin
    Stockholm University, Faculty of Humanities, Department of Archaeology and Classical Studies, Archaeological Research Laboratory.
    Jakobsson, Mattias
    Barnes, Ian
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    Lister, Adrian
    Dalen, Love
    Microsatellite genotyping reveals end-Pleistocene decline in mammoth autosomal genetic variation2012In: Molecular Ecology, ISSN 0962-1083, E-ISSN 1365-294X, Vol. 21, no 14, p. 3391-3402Article in journal (Refereed)
    Abstract [en]

    The last glaciation was a dynamic period with strong impact on the demography of many species and populations. In recent years, mitochondrial DNA sequences retrieved from radiocarbon-dated remains have provided novel insights into the history of Late Pleistocene populations. However, genotyping of loci from the nuclear genome may provide enhanced resolution of population-level changes. Here, we use four autosomal microsatellite DNA markers to investigate the demographic history of woolly mammoths (Mammuthus primigenius) in north-eastern Siberia from before 60 000 years ago up until the species final disappearance c. 4000 years ago. We identified two genetic groups, implying a marked temporal genetic differentiation between samples with radiocarbon ages older than 12 thousand radiocarbon years before present (ka) and those younger than 9 ka. Simulation-based analysis indicates that this dramatic change in genetic composition, which included a decrease in individual heterozygosity of approximately 30%, was due to a multifold reduction in effective population size. A corresponding reduction in genetic variation was also detected in the mitochondrial DNA, where about 65% of the diversity was lost. We observed no further loss in genetic variation during the Holocene, which suggests a rapid final extinction event.

  • 137.
    Nyström, Veronica
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Humphrey, Joanne
    Skoglund, Pontus
    McKeown, Niall
    Jakobsson, Mattias
    Vartanyan, Sergey
    Lidén, Kerstin
    Stockholm University, Faculty of Humanities, Department of Archaeology and Classical Studies.
    Barnes, Ian
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    Lister, Adrian
    Dalén, Love
    Stockholm University, Faculty of Science, Department of Zoology.
    Microsatellite genotyping reveals end-Pleistocene shift in mammoth autosomal genetic variationManuscript (preprint) (Other academic)
  • 138. Ranc, Nathan
    et al.
    Santini, Luca
    Rondinini, Carlo
    Boitani, Luigi
    Poitevin, Françoise
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    Maiorano, Luigi
    Performance tradeoffs in target-group bias correction for species distribution models2017In: Ecography, ISSN 0906-7590, E-ISSN 1600-0587, Vol. 40, no 9, p. 1076-1087Article in journal (Refereed)
    Abstract [en]

    Species distribution models (SDMs) are often calibrated using presence-only datasets plagued with environmental sampling bias, which leads to a decrease of model accuracy. In order to compensate for this bias, it has been suggested that background data (or pseudoabsences) should represent the area that has been sampled. However, spatially-explicit knowledge of sampling effort is rarely available. In multi-species studies, sampling effort has been inferred following the target-group (TG) approach, where aggregated occurrence of TG species informs the selection of background data. However, little is known about the species-specific response to this type of bias correction. The present study aims at evaluating the impacts of sampling bias and bias correction on SDM performance. To this end, we designed a realistic system of sampling bias and virtual species based on 92 terrestrial mammal species occurring in the Mediterranean basin. We manipulated presence and background data selection to calibrate four SDM types. Unbiased (unbiased presence data) and biased (biased presence data) SDMs were calibrated using randomly distributed background data. We used real and TG-estimated sampling efforts in background selection to correct for sampling bias in presence data. Overall, environmental sampling bias had a deleterious effect on SDM performance. In addition, bias correction improved model accuracy, and especially when based on spatially-explicit knowledge of sampling effort. However, our results highlight important species-specific variations in susceptibility to sampling bias, which were largely explained by range size: widely-distributed species were most vulnerable to sampling bias and bias correction was even detrimental for narrow-ranging species. Furthermore, spatial discrepancies in SDM predictions suggest that bias correction effectively replaces an underestimation bias with an overestimation bias, particularly in areas of low sampling intensity. Thus, our results call for a better estimation of sampling effort in multispecies system, and cautions the uninformed and automatic application of TG bias correction.

  • 139.
    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.

  • 140.
    Stensland, Eva
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    Berggren, Per
    Stockholm University, Faculty of Science, Department of Zoology.
    Mixed species groups in mammals2003In: Mammal Review, ISSN 0305-1838, E-ISSN 1365-2907, Vol. 33, no 3, p. 205-223Article in journal (Refereed)
    Abstract [en]

    1. Mixed species groups have long been noted in birds, but they also occur among different species of mammals ranging from closely related species to species from different orders. Mixed species groups of mammals occur in many different habitats, e.g. ungulates on the savannah, primates in various types of forests and cetaceans in the oceans. Mixed species groups are very different in their duration, frequency, predominant activity and structure depending on the species interacting and the habitat they occur in. 2. Functional explanations for mixed species groups usually fall within two categories: foraging advantages and predator avoidance. However, there could also be other social and reproductive advantages of mixed species groups that could contribute to their formation and stability. The advantages do not have to be equally distributed between the participating species and can also vary according to season and the presence of predators. 3. It is important that all investigators of mixed species groups take their studies one step further after the naturalistic description and test the function and benefits of mixed species groups in order to give more strength to their conclusions. In this paper we review and discuss the function of mixed species groups in mammals and suggest an approach on how to investigate the function of such groups.

  • 141.
    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.

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  • 142.
    Särnblad, Anna
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Dalén, Love
    Stockholm University, Faculty of Science, Department of Zoology.
    Kiszka, Jeremy
    Collins, Tim
    Amir, Omar A.
    Stockholm University, Faculty of Science, Department of Zoology.
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    Berggren, Per
    Stockholm University, Faculty of Science, Department of Zoology.
    Population structure and diversity of Indo-Pacific bottlenose dolphins (Tursiops aduncus) in the western Indian OceanManuscript (preprint) (Other academic)
    Abstract [en]

    Bottlenose dolphin (Tursiops sp.) populations often show small-scale genetic differentiation and have a capacity to adapt both their social strategies and structure to local environmental conditions. Here we investigate population structure and genetic diversity of Indo-Pacific bottlenose dolphins (Tursiops aduncus) in the western Indian Ocean, with special reference to Zanzibar, Tanzania. The Indo-Pacific bottlenose dolphins off Zanzibar were previously hunted and are subject to high levels of bycatch and negative impact from tourism. A recent study has indicated a limited exchange of reproducing females between northern and southern Zanzibar. Mitochondrial DNA sequence (mtDNA 429bp) variation and autosomal genotypes (7 microsatellite loci) was used to assess genetic variation and differentiation among tissue samples from Zanzibar (n=91) Mayotte (n=12) and Oman (n=4). The results showed a much higher amount of differentiation for mtDNA than autosomal DNA between northern and southern Zanzibar suggesting female philopatry with greater dispersal by males than females. Genetic diversity levels were relatively high in all areas and there were no indications of any recent reduction in effective population size, except in Mayotte where indications of a recent bottleneck encourage further analyses. Further, the close relationship and lack of clear structuring, with several shared haplotypes among regions, suggest a relatively recent common founder population for the Indo-Pacific bottlenose dolphins in the western Indian Ocean. Based on the high differentiation in mtDNA between northern and southern Zanzibar and that local growth rates in large part will be determined by female breeding success, we suggest that the Indo-Pacific bottlenose dolphins off northern and southern Zanzibar should be treated as separate management units.

  • 143.
    Tannerfeldt, Magnus
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    Fluctuating resources and the evolution of litter size in the arctic fox1998In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 83, no 3, p. 545-559Article in journal (Refereed)
    Abstract [en]

    Fluctuations in essential resources cause a strong selection pressure on the ability to adjust parental investment accordingly. In the dog family, Canidae, variance in female prebirth investment is adjusted by litter size. The arctic fox, Alopex lagopus, is a small canid living on the northern tundras of the world. It has the largest known litter size in the order Carnivora. up to 18 young, and litter size is highly variable. We have analysed data From arctic fox populations throughout the species circumpolar range. In some areas, arctic foxes feed on strongly fluctuating populations of small rodents. In contrast, they have more stable food resources at bird cliffs and along coast lines. Food availability determines arctic fos litter and population sizes. A comparison between fluctuating and stable arctic fox populations showed that fluctuations are associated with large litter sizes. There were significant differences in litter size means, maxima and variances, as well as in placental scar count means. We have discussed five hypotheses on the determination of variation in litter size: one energetic, one genetic (based on density variation), one diet-determined, one based on reproductive allocation and one based on differences in reaction norms. Our findings suggest that litter size in the arctic fox is determined by the combined effect of immediate resource levels and the degree of resource predictability. We describe reaction norms that suggest how litter sizes result from adaptive plasticity within each of two genetic strategies where, according to the jackpot hypothesis, populations with unpredictable food resources generally have larger litter sizes. Within each genetic strategy, or reaction norm, litter sizes are adjusted through a number of plastic trails. These traits are influenced by nutritional limitations and include reduced ovulation rates, prenatal losses, and litter size reduction during the lactation period.

  • 144.
    Tannerfeldt, Magnus
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    Life history strategies in a fluctuating environment: establishment and reproductive success in the arctic fox1996In: Ecography, ISSN 0906-7590, E-ISSN 1600-0587, Vol. 19, no 3, p. 209-220Article in journal (Refereed)
    Abstract [en]

    Natal dispersal, territoriality and reproductive success can have a major impact on the range, genetics and risk of extinction of a population. The proportions of animals that disperse have often been investigated, but not their fate. We have studied the lifetime reproductive success of arctic foxes that successfully emigrated, travelled and settled. Of these, some settled in the vicinity of their natal site as residents and some immigrated from other ai eas, i.e. short- and long-range dispersers respectively. We round no seu bias in migration patterns. In presaturation years, more immigrants residents settled. Immigrant females had higher reproductive success than resident females. There was strong support for the ultimate hypothesis of Competition For Resources (CFR), but not for tile hypotheses of Competition For Mates (CFM), Resident Fitness (RFH) and Inbreeding Avoidance (IA). Our data on arctic foxes could not be fully explained by and of four proximate hypotheses. We suggest that the reason is that dispersal and establishment should be considered as state dependent life history characteristics of individuals rather than population averages.

  • 145.
    Tannerfeldt, Magnus
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    Arvidson, Bengt
    Stockholm University, Faculty of Science, Department of Zoology.
    The Effect of Summer Feeding on Juvenile Arctic Fox Survival - a Field Experiment1994In: Ecography, ISSN 0906-7590, E-ISSN 1600-0587, Vol. 17, no 1, p. 88-96Article in journal (Refereed)
    Abstract [en]

    The arctic fox Alopex lagopus L. population in Sweden is small and its numbers fluctuate widely with food availability, i.e. rodent populations. This fluctuation is mediated through differences in recruitment rates between years. The recruitment can be divided into three phases: number of litters born, number of cubs per litter and cub survival rates. The number of litters and their sizes have been shown to depend on food availability during winter and spring. To examine cub survival during the summer and how it relates to food availability, we conducted a feeding experiment in northern Sweden during 1990, a year of low rodent density, involving six occupied arctic fox dens. Feeding at dens lowered cub mortality rates. However, condition and growth rates of juveniles were not influenced by supplementary feeding at dens, nor were they related to the probability of survival for an individual. Thus arctic foxes seem to minimize risks rather than maximize growth. The juvenile mortality from weaning and over the next 6 wk was 21%, mostly due to starvation. Only 8.2% survived from weaning to the first breeding season. Of the one-year-old foxes, 50% survived their second year. Supplementary feeding of juveniles had no effect on the final survival rates over these two years. However, the immediate, positive effect on cub survival could be used in a long-term, extensive management programme if combined with winter feeding.

  • 146.
    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.

  • 147.
    Taylor, Alexandra K.
    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.
    Effects of trap density and duration on vole abundance indices2011In: Annales Zoologici Fennici, ISSN 0003-455X, E-ISSN 1797-2450, Vol. 48, no 1, p. 45-55Article in journal (Refereed)
    Abstract [en]

    This study aims to investigate if patterns of immigration by voles into removal plots on the third day of trapping are evident in the grey-sided vole, and if altering the number of traps at each station will result in increased precision of the vole abundance estimate. Traps were placed using the small quadrat method, with one, three, or five traps placed at each corner. Traps were checked twice a day for five days. Mixed-effect models were used to investigate the relationship between the number of traps and the length of time the traps were out on the abundance index. There was no difference between having three or five traps. Having one trap resulted in an inflated estimate. Five traps had the highest number of successful trapping events, reducing the number of zeros in the data set and leaving fewer individuals unaccounted. There was a peak in catches on the third day, driven by younger individuals and by males. These are suspected immigrants that are exploiting the territories left by individuals trapped in the first two days, suggesting this is not a closed system.

  • 148. Tietgen, Lukas
    et al.
    Hagen, Ingerid J.
    Kleven, Oddmund
    Di Bernardi, Cecilia
    Kvalnes, Thomas
    Norén, Karin
    Stockholm University, Faculty of Science, Department of Zoology.
    Hasselgren, Malin
    Stockholm University, Faculty of Science, Department of Zoology.
    Wallén, Johan Fredrik
    Stockholm University, Faculty of Science, Department of Zoology. Swedish Museum of Natural History, Sweden.
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    Landa, Arild
    Eide, Nina E.
    Flagstad, Øystein
    Jensen, Henrik
    Fur colour in the Arctic fox: genetic architecture and consequences for fitness2021In: Proceedings of the Royal Society of London. Biological Sciences, ISSN 0962-8452, E-ISSN 1471-2954, Vol. 288, no 1959, article id 20211452Article in journal (Refereed)
    Abstract [en]

    Genome-wide association studies provide good opportunities for studying the genetic basis of adaptive traits in wild populations. Yet, previous studies often failed to identify major effect genes. In this study, we used high-density single nucleotide polymorphism and individual fitness data from a wild non-model species. Using a whole-genome approach, we identified the MC1R gene as the sole causal gene underlying Arctic fox Vulpes lagopus fur colour. Further, we showed the adaptive importance of fur colour genotypes through measures of fitness that link ecological and evolutionary processes. We found a tendency for blue foxes that are heterozygous at the fur colour locus to have higher fitness than homozygous white foxes. The effect of genotype on fitness was independent of winter duration but varied with prey availability, with the strongest effect in years of increasing rodent populations. MC1R is located in a genomic region with high gene density, and we discuss the potential for indirect selection through linkage and pleiotropy. Our study shows that whole-genome analyses can be successfully applied to wild species and identify major effect genes underlying adaptive traits. Furthermore, we show how this approach can be used to identify knowledge gaps in our understanding of interactions between ecology and evolution.

  • 149. Tirronen, Konstantin
    et al.
    Ehrich, Dorothee
    Panchenko, Danila
    Dalén, Love
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    The Arctic fox (Vulpes lagopus L.) on the Kola Peninsula (Russia): silently disappearing in the mist of data deficiency?2021In: Polar Biology, ISSN 0722-4060, E-ISSN 1432-2056, Vol. 44, p. 913-925Article in journal (Refereed)
    Abstract [en]

    The Arctic fox (Vulpes lagopus L.) population on the Kola Peninsula occupies an intermediate, and potentially connecting, position between foxes living on the Scandinavian Peninsula and populations further east in Russia, but very little is known about the status of this population. Here we summarize data from the literature, forgotten archival sources about research in the first half of the twentieth century, and the results of several independent expeditions undertaken over the past two decades. These materials include data on fur harvesting, incomplete monitoring data from official winter track counts of game animals, local knowledge, and our own observations. Our research revealed the extremely poor state of the Arctic fox population on the Kola Peninsula. According to our estimates, the current population is likely isolated and consists of no more than a few dozen adults. The fur return data, together with long-term data on small rodent abundance, suggest that irregular and fading out lemming cycles were a major driver of the Arctic fox population decline. The thorough research from the 1930s contrasts strongly with the lack of interest in studying and monitoring the population in recent decades, which is not even listed as a threatened species in the regional Red Data Book. In fact, the work performed here filled a more than a half-century gap in the study of the population and allowed us to determine the urgent need to resume research and immediately take active measures to protect and promote the recovery of the species in the region.

  • 150. Unnsteinsdottir, E. R.
    et al.
    Hersteinsson, P.
    Pálsson, S.
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    The fall and rise of the Icelandic Arctic fox (Vulpes lagopus): a 50-year demographic study on a non-cyclic Arctic fox population2016In: Oecologia, ISSN 0029-8549, E-ISSN 1432-1939, Vol. 181, no 4, p. 1129-1138Article in journal (Refereed)
    Abstract [en]

    In territorial species, observed density dependence is often manifest in lowered reproductive output at high population density where individuals have fewer resources or are forced to inhabit low-quality territories. The Arctic fox (Vulpes lagopus) in Iceland is territorial throughout the year and feeds mostly on birds, since lemmings are absent from the country. Thus, the population does not exhibit short-term population cycles that are evident in most of the species' geographical range. The population has, however, gone through a major long-term fluctuation in population size. Because of the stability in hunting effort and reliable hunting records since 1958, the total number of adult foxes killed annually can be used as an index of population size (N (t) ). An index of carrying capacity (K) from population growth data for five separate time blocks during 1958-2007 revealed considerable variation in K and allowed a novel definition of population density in terms of K, or N (t) /K. Correlation analysis suggested that the reproductive rate was largely determined by the proportion of territorial foxes in the population. Variation in litter size and cub mortality was, on the other hand, related to climatic variation. Thus, Arctic foxes in Iceland engage in typical contest competition but can adapt their territory sizes in response to both temporal and spatial variation in carrying capacity, resulting in surprisingly little variation in litter size.

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