Proximate factors affecting snowshoe hare movements during a cyclic population low phase

Abstract

Animals change their movements in response to food supply and predation risk. Such behavioural shifts can affect reproduction and survival, especially if animals are forced to trade off between food and safety. I studied snowshoe hares (Lepus americanus Erxleben) during a low phase of the ten-year cycle in the southern Yukon. I used a factorial manipulation of food addition and predator reduction to determine how predators, food supply, and hare density affect hare movements. Control hares were more active than hares protected from predators or hares given supplemental food. Female hares showed no change in home range size or winter travel rates with these treatments, but females protected from predators had lower summer travel rates than did control females. Male hares protected from predators had lower travel rates in both seasons and smaller home ranges than did males exposed to mammalian predators. Male hares generally had higher movements than did females, but neither sex responded to a ~5-fold change in density. The results indicate that different movement indices have distinct functions that may differ with sex. Not all movement types are necessarily affected by predation risk, food availability, or density. The increase in movements with higher risk is unusual, because most small mammals reduce movements when predation risk is high. For snowshoe hares, safety may increase by moving away from predators and using larger areas.