Using a spatially explicit model to understand the impact of search rate and search distance on spatial heterogeneity within an herbivore grazing system

The importance of animal selection behaviour in determining spatial structure of grazing systems has implications for sustainable grazing management. Although changes in stocking density provide a mechanism for direct control of animal impact, grazing behaviour is also responsible for influencing vegetation dynamics. A spatially explicit grazing model was used to explore the impact of movement in search of higher intake (search rate) and search distance on spatial sward structure, specifically the distribution of sward surface height. The model simulated a two-stage grazing process in heterogeneous environments i.e. searching then biting. As search rate and search distance increased so the spatial variance of sward structure decreased. Changes in herbivore search rate have a greater impact on spatial variance of pastoral grazing systems than search distance. Herbivores foraging in heterogeneous environments with greater search rates may better utilise the available forage resources. Higher search rates in natural and agricultural systems may determine herbivore fitness and survival or production, respectively.