Provisioning time and central-place foraging in beavers

Abstract
Field studies suggest that beavers are increasingly selective the farther they forage from the lodge. This could result either from spatial variation in food availability (as predicted by classic contingency foraging models) or from the provisioning time (as predicted by central-place foraging models). We tested the effect of provisioning time by providing beavers in experimental enclosures with equal frequencies of saplings at various distances from the lodge and we compared the patterns of resource use with the predictions from an explicit model of central-place foraging. The model qualitatively predicted the observed patterns of increase in the mean size of aspen and maple saplings utilized and the decrease in the variance of saplings utilized, at distances ranging between 10 and 40 m, but there was evidence that the degree of selectivity by beavers increased more rapidly with distance than predicted by the model. No size–distance relations were apparent when beavers were presented with alders. Our results suggest that provisioning time is an important determinant of resource exploitation patterns by beavers, at least in some forage species.