Linking Habitat Selection and Predation Risk to Spatial Variation in Fitness for Woodland Caribou

Abstract

A central assumption underlying niche theory and the study of habitat selection is that selected habitats confer enhanced fitness. Here, we separately measured spatial patterns of both resource selection and predation risk and tested their relationships with a key demographic fitness trait, adult female survival, for a threatened ungulate, woodland caribou (Rangifer tarandus caribou). We used Cox-proportional hazards spatial survival modeling to assess support for various selection- and risk-based estimates of habitat quality using previously developed caribou resource selection functions and wolf predation risk models. Indeed we found positive relationships between the predicted values of a scale-integrated resource selection function and survival, yet subsequently incorporating predation risk greatly improved models further. Predation risk was an additive source of hazard beyond that detected through selection alone, and selection thus shown to be non-ideal. Furthermore, by combining spatially-explicit adult female survival predictions with herd-specific estimates of recruitment in matrix population models, we demographically estimated a fitness landscape for this threatened species.