A THEORETICAL BASIS FOR STUDY AND MANAGEMENT OF TRAMPLING BY CATTLE

Cattle trampling of endangered plants, certain animal species, and gro und nests may be a management concern on rangeland, Researchers need t heoretical models of trampling lass to assist in design of studies and interpretation of results, Managers can use such models to assist in grazing management decisions, We present null (random background) mode ls for predicting probability of trampling loss, explore the effects o f failure of assumptions underlying these models, and develop alternat ive models for dealing with nonrandom grazing and nonrandom placement of vulnerable objects, The null models predict that if time-based stoc king rate (head-days ha(-1)) is held constant and 1 pasture is grazed under several rotation schedules (a study design used to simulate rota tional grazing), or if 1 pasture is divided into n paddocks through wh ich 1 herd rotates, the probability of trampling is operationally cons tant. This qualitative prediction holds when grazing is nonindependent and nonrandom, competing risks exist, and objects subject to tramplin g are dispersed nonrandomly, Quantitative predictions of the null mode ls do not hold under nonrandom grazing, which is expected to reduce pr obability of trampling, Researchers can use predictions of the models as a priori hypotheses, If empirical results deviate from the predicti ons, then researchers should search for the underlying cause-effect me chanisms, For management, the models indicate that trampling varies wi th livestock density and time grazed but is independent of herd rotati on.