Vigilance by female dall's sheep: interactions between predation risk factors

摘要

Data on adult female Dall's Ovis dalli dalli, were used to assess how predation risk factors combine to affect vigilance. An interactive factors hypothesis was proposed, and whether predation risk factors have interactive (or multiplicative) effects on vigilance was tested. Because most studies have implicitly assumed additivity, for illustrative purposes the alternative but less plausible independent factors hypothesis, in which predation risk factors have independent (or additive) effects on vigilance, was also tested.