Spatial scale in games of habitat selection, patch use, and sympatric speciation

Abstract

Most organisms live in heterogeneous environments. Yet we know little about how variations in scales of heterogeneity influence decisions on patch use and habitat selection, and how they impact spatial distribution and evolution. In particular, we need to know whether the choice of habitats and patches emerges from a hierarchy of decisions, whether resource consumption correlates closely with space use, and whether different types of individuals are associated with patterns of spatial distribution. I address these knowledge gaps with field experiments that manipulated the risk and quality of foraging patches exploited by male meadow voles. I used clear versus wooden covers to create risky versus safe foraging sites and added supplemental food to create rich versus poor habitats. I assessed whether the resources harvested from each tray matched its frequency of use by groups of voles expressing different temperament scores. Habitat and patch use did not fit a simple hierarchy of decisions because animals merged space use and foraging speed in a sophisticated strategy of risk management. Giving-up densities mirrored activity densities at the scale of safe versus risky patches but not at the scale of safe versus risky or rich versus poor habitats. Voles tended to prefer one habitat over another for reasons independent of the experimental manipulations. Groups of voles with different temperament scores were not linked to foraging types but were linked to habitat preference. The bias in habitat use by different behavioural types provides a potential mechanism for the evolutionary divergence of populations occupying different habitats.