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Spatial distribution in Norwegian lemming Lemmus lemmus in relation to the phase of the cycle
Stockholm University, Faculty of Science, Department of Zoology.
Stockholm University, Faculty of Science, Department of Zoology.ORCID iD: 0000-0002-9207-5709
Stockholm University, Faculty of Science, Department of Zoology.ORCID iD: 0000-0001-5496-4727
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2018 (English)In: Polar Biology, ISSN 0722-4060, E-ISSN 1432-2056, Vol. 41, no 7, p. 1391-1403Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
2018. Vol. 41, no 7, p. 1391-1403
Keywords [en]
Small rodents, Density-dependent, Competition, Habitat, Primary productivity
National Category
Ecology
Research subject
Animal Ecology
Identifiers
URN: urn:nbn:se:su:diva-153974DOI: 10.1007/s00300-018-2293-6ISI: 000437102400007OAI: oai:DiVA.org:su-153974DiVA, id: diva2:1189419
Projects
Svenska fjällrävsprojektet
Funder
Interreg Sweden-NorwayAvailable from: 2018-03-09 Created: 2018-03-09 Last updated: 2018-12-04Bibliographically approved
In thesis
1. Spatial and temporal population dynamics in the mountain tundra – mesopredator and prey
Open this publication in new window or tab >>Spatial and temporal population dynamics in the mountain tundra – mesopredator and prey
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

It is well known that competition, predation and fluctuating food resources can have strong effect on individual fitness and population dynamics. The complexity of natural systems can make it complicate to disentangle those processes, but environments with relatively simple food webs, and strong cyclic population dynamics offer contrasting conditions resembling experimental treatments. This thesis concerns the spatial and temporal implications of fluctuations in small rodent abundance on two trophic levels in a highly cyclic ecosystem, the Scandinavian mountain tundra. The first two chapters focus on plant biomass and spatiotemporal distribution in the Norwegian lemming (Lemmus lemmus), while the three last papers focus on the direct and indirect effects of small rodent fluctuations and territory quality on reproductive success, juvenile survival and group living in a lemming specialist mesopredator, the arctic fox (Vulpes lagopus). By developing, validating and applying a novel application of aerial photos for remote sensing of plant biomass (Chapter I), we found that food availability predicted lemming distribution during population peaks, but that they were more habitat specific during increase years when intraspecific competition was lower (Chapter II). Arctic fox reproduction is tightly connected to small rodent abundance but the effects of geographical variation in food availability is less well known. We used 17 years of population surveys of an arctic fox subpopulation in mid Sweden (Helagsfjällen) to investigate potential effects. During small rodent increase years, we found that arctic fox litter sizes were smaller in territories of intermediate plant productivity, compared to both more and less productive territories (Chapter III). This could be an effect of limited food availability together with increased presence of red foxes (Vulpes vulpes), a stronger and potentially lethal competitor. However, when small rodents peaked, and competition would be expected to decrease, we saw no effect of territory productivity. Based on a smaller data set concerning juvenile summer survival, we found that the mortality rate among juveniles born by first time breeding arctic fox females were more sensitive to low small rodent prey abundance (Chapter IV). We explain it with an increased predation pressure from top-predators that switch from small rodents to alternative prey when small rodents decline, as suggested by an observed positive effect on juvenile survival by adult presence on den sites. Arctic foxes are socially flexible, and several adults can share a den with the resident pair, potentially increasing juvenile survival and help in territorial defence. Returning to the 17-year data set, we tested the Resource Dispersion Hypothesis predicting that increased resource availability should increase group size (Chapter V). We found support for this prediction as group living increased during the small rodent peak phase. However, it remained unexpectedly high during the decrease phase, when resources are scarce. This could however be related to increased predation pressure, and an increasing benefit of group living.

Place, publisher, year, edition, pages
Stockholm: Department of Zoology, Stockholm University, 2019. p. 17
Keywords
population dynamics, cyclic, mountain tundra, arctic fox, Norwegian lemming, small rodents, mesopredator, predation, survival, reproduction
National Category
Zoology Ecology
Research subject
Animal Ecology
Identifiers
urn:nbn:se:su:diva-162539 (URN)978-91-7797-540-3 (ISBN)978-91-7797-541-0 (ISBN)
Public defence
2019-01-25, Vivi Täckholmsalen (Q-salen), NPQ-huset, Svante Arrhenius väg 20, Stockholm, 10:00 (English)
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Note

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 1: Manuscript. Paper 3: Manuscript. Paper 5: Manuscript.

Available from: 2018-12-19 Created: 2018-11-30 Last updated: 2020-05-11Bibliographically approved

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