Linking physiological effects on activity and resource use to population level phenomena

Abstract

We present an approach to delineating physiological effects on population level processes by modeling the activity and resource budgets of animals. Physiology and its environmental forcing functions are assumed to affect both the total time available for activity and foraging and the resource budgets by affecting resource acquisition, costs, and handling. We extend the earlier model of Dunham and others (1989) and translate it into a computational algorithm. To satisfy conservation needs for accuracy, wide applicability, and rapid deployment, the model is relatively simple, uses as much data on the focal organism as possible, is mechanistically driven, and can be adapted to new organisms by using data for the new species, or the best available approximations to those data. We present 2 applications of the modeling approach. First, we consider a system with substantial information available, canyon lizards (Sceloporus merriami) studied by Dunham and colleagues in west Texas. In this case the focus is on integration of numerous inputs and the ability of the model to produce predictions that approximate counterintuitive empirical patterns. By using the wealth of specific data available, the model outperforms previous attempts at explanation of those patterns. Next, we consider a system with much less available information (forest-dwelling semi-fossorial frogs). The question here is how hydric conditions can become limiting. A model of evaporation from frogs buried in leaf litter was incorporated and it demonstrates how rainfall patterns can both supply water and put the frogs at risk of critical dehydration.