Spatial Ecology of Wolverines in Scandinavia

by May, Roelof Frans

1. Conservation of carnivores in an increasingly changing environment is much enhanced by understanding the decision-making processes underlying habitat patch choice. In a fluctuating environment incorporation of spatio-temporal activity patterns and home range use in resource selection models enhances the biological meaning of behavioural choices animals make along their path. Especially for central place foragers, such as the wolverine Gulo gulo L., the nature and strength of the trade-off between central place foraging and optimal foraging are likely to influence both spatio-temporal movement patterns and patch choice. 2. We investigated the spatio-temporal ranging behaviour of seven reproductive female wolverines in south-central Norway, based on GPS data collected in 2002-2005. The study was conducted using autoregressive models and discrete choice models, which incorporated individual preferences. Travel speed, home range use and selection for elevation were analysed in relation to spatial and temporal covariates (time-of-day and date). 3. Wolverines were more active during the night and in the home range periphery. The stronger selection for higher elevations towards the periphery of the wolverines’ home ranges may be explained in two ways: (1) the location of the optimal central place lies in the “centre of gravity” of the food distribution, or (2) peripheral locations represent ranging movements for the purpose of transportation from patch to patch or central place. Over the summer, travel speed decreased and preference for lower-lying patches at day time increased, indicating a diminishing central place foraging movement pattern. At night wolverines selected similar patches at lower elevations all through the summer, enabling them to forage in the forest–alpine tundra ecotone; likely to be the patch with the highest expected profitability. May et al. – Spatio-temporal ranging behaviour in wolverines 3/36 4. The elevation preferences throughout the summer clearly showed a change from central place foraging to optimal foraging in wolverines with dependent cubs. Whereas in the beginning of the summer cubs are placed at rendezvous sites, towards the end of the summer cubs grow more mobile and independent. Apparently, female wolverines are faced with a continuous, but diminishing, trade-off between providing food and shelter for their offspring throughout the summer.