SEARCH COSTS AND HABITAT SELECTION BY DISPERSERS

Abstract

The effects of search costs on habitat selection by dispersers are largely unknown. We explore how habitat selection behavior is affected by the risk of mortality en route and by deferred search costs (i.e., costs incurred during search that reduce fitness after arrival in the new habitat), using a model designed for long-distance natal dispersers searching for scarce patches of suitable habitat embedded within a matrix of unsuitable habitat. In this situation, increases in the risk of mortality during search reduce disperser selectivity, where selectivity is reflected by the period during search when dispersers are only willing to accept a high-quality habitat. However, the effects of deferred costs on selectivity depend on other factors with pronounced effects on selectivity, including encounter rates with high-quality habitats, relative habitat quality, and total search time. Surprisingly, under some sets of conditions, increases in deferred costs lead to increases in disperser selectivity. Overall, the effects of mortality and deferred costs on selectivity are small relative to the effects of other factors on selectivity. For instance, our model suggests that selectivity is much more strongly affected by total search time than by search costs, and it predicts a positive relationship between total search time and disperser selectivity across individuals in the same population, even in the face of considerable inter-individual variation in risk of mortality or deferred search costs.