Hierarchical foraging models: Effects of stocking and landscape composition on simulated resource use by cattle

Abstract

This study tested the sensitivity of a hierarchical foraging model to plant community composition, landscape composition and cattle stocking rate. Diet selection was represented as an overmatching process. Relative species preference (proportion in diet/proportion in herbage) was expressed as an exponential function of relative palatability. Habitat selection was described as a biased matching response in which relative community preference (proportional foraging time/proportional area) was a linear function of relative availability of food plants, weighted by palatability. Interaction of palatability and availability effects resulted in complex diet selection responses to community composition; response of landscape utilization to community availability was simpler and less volatile. Simulated experiments suggested that diet selection was more sensitive to stocking rate than was plant community use. Results have implications for the efficacy of grazing management as a tool for manipulating livestock foraging behavior. Intensive grazing systems may simulate the effects of high stocking rate on diet selection, thereby resulting in decreased expression of species preferences. Patterns of landscape use may be strongly influenced by landscape composition but only weakly influenced by grazing management.