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The resource dispersion hypothesis – a test with a cyclic mesopredator
Stockholm University, Faculty of Science, Department of Zoology, Animal Ecology.ORCID iD: 0000-0002-9207-5709
Stockholm University, Faculty of Science, Department of Zoology, Animal Ecology.ORCID iD: 0000-0002-4875-4413
Stockholm University, Faculty of Science, Department of Zoology, Animal Ecology.ORCID iD: 0000-0001-5535-9086
Stockholm University, Faculty of Science, Department of Zoology, Animal Ecology.ORCID iD: 0000-0002-9707-5206
(English)Manuscript (preprint) (Other academic)
National Category
Ecology
Research subject
Animal Ecology
Identifiers
URN: urn:nbn:se:su:diva-162538OAI: oai:DiVA.org:su-162538DiVA, id: diva2:1267129
Available from: 2018-11-30 Created: 2018-11-30 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)
Opponent
Supervisors
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: 2019-02-04Bibliographically approved

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Erlandsson, RasmusHasselgren, MalinAngerbjörn, AndersNorén, Karin
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