ARCUS | Arctic Research Consortium of the United States

6th Annual ARCUS Award for Arctic Research Excellence


Submitted by   Mette Mauritzen
Authors   Mette Mauritzen, S.E. Belikov, A.N. Boltunov, A.E. Derocher, E. Hansen, R.A. Ims, Ø. Wiig, and N. Yoccoz
Category   Life Science
Title   Functional responses in polar bear habitat selection.
Affiliation   Zoological Museum, University of Oslo, 5817 Bergen, Norway

Abstract

Habitat selection may occur in situations in which animals experience a trade-off, e.g. between the use of habitats with abundant forage and the use of safer retreat habitats with little forage. Such trade-offs may yield relative habitat use conditional on the relative availability of the different habitat types and thus result in functional responses in habitat use (i.e. change in relative use with changing availability). We used logistic and log-linear models to model functional responses in polar bear habitat use based on satellite telemetry data from two contiguous populations; one near shore inhabiting sea ice within fjords, and one inhabiting pelagic drift ice. The pelagic areas along the sea ice edge are hypothesized to be important polar bear habitat with high prey availability. These habitats are highly dynamic due to continuous alterations made by wind, currents and changing temperature. In such habitats polar bears may experience a high energetic cost of movements and risk drifting away from the main ice field. If polar bears were constrained by ice dynamics we therefore predicted use of retreat habitats with greater ice coverage relative to habitats used for hunting. The polar bears demonstrated season and population specific functional responses in habitat use, likely reflecting seasonal and regional variation in use of retreat habitats and in habitat specific seal availability. We suggest that in seasons with functional responses in habitat use, polar bear space use and population distribution may not be a mere reflection of prey availability but rather reflect the alternate allocation of time in hunting and retreat habitats.