Females roam while males patrol: divergence in breeding season movements of pack-ice polar bears (Ursus maritimus) |
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Authors: | Kristin L Laidre Erik W Born Eliezer Gurarie ?ystein Wiig Rune Dietz Harry Stern |
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Institution: | 1.Polar Science Center, APL, University of Washington, Seattle, WA 98105, USA;2.Department of Statistics, University of Washington, Seattle, WA 98105, USA;3.Greenland Institute of Natural Resources, PO Box 570, 3900 Nuuk, Greenland;4.National Centre for Biosystematics, Natural History Museum, University of Oslo, PO Box 1172, Blindern, 0318 Oslo, Norway;5.Institute of Bioscience, Arctic Research Centre, Aarhus University, PO Box 358, 4000 Roskilde, Denmark |
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Abstract: | Intraspecific differences in movement behaviour reflect different tactics used by individuals or sexes to favour strategies that maximize fitness. We report movement data collected from n = 23 adult male polar bears with novel ear-attached transmitters in two separate pack ice subpopulations over five breeding seasons. We compared movements with n = 26 concurrently tagged adult females, and analysed velocities, movement tortuosity, range sizes and habitat selection with respect to sex, reproductive status and body mass. There were no differences in 4-day displacements or sea ice habitat selection for sex or population. By contrast, adult females in all years and both populations had significantly more linear movements and significantly larger breeding range sizes than males. We hypothesized that differences were related to encounter rates, and used observed movement metrics to parametrize a simulation model of male–male and male–female encounter. The simulation showed that the more tortuous movement of males leads to significantly longer times to male–male encounter, while having little impact on male–female encounter. By contrast, linear movements of females are consistent with a prioritized search for sparsely distributed prey. These results suggest a possible mechanism for explaining the smaller breeding range sizes of some solitary male carnivores compared to females. |
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Keywords: | ursids polar bear Greenland breeding season pair formation tortuosity |
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