How do snowshoe hares manage the risk of being eaten?
The short lives of snowshoe hares are filled with danger. For most, death comes quickly through the teeth or talons of predators. Hares have only two modes of defense — hide from or evade their predators. But they also have to eat during the dark cold days of winter when food is limited and hungry predators abound. How do hares manage the competing interests of food versus safety?
Theory and common sense tell us that hares should eat less and be more vigilant when risk is high and should eat more and be less vigilant when risk is low. I tested these conjectures by giving hares a choice to eat one of their preferred winter foods under differing levels of safety.
Read this open access paper on the FACETS website.
Wildlife cameras recorded the hares’ behaviour while they ate pairs of jack-pine boughs stuck in the snow. Hares could choose to eat from a patch in the open or a nearby patch located in dense alder scrub — cover that the hares use to escape from predators.
When predators were abundant and risk was high, hares were more vigilant in the alder than they were in the open. The safety of the alders reduces visibility, so hares increase vigilance to detect predators in time to escape. When predators were absent and risk was low, hares were more vigilant in risky open habitat far from safety. This pattern occurred only when hares were most visible to predators during the full moon. Hares foraged less in the open in each experiment but only when far from the safety of alders.
The results demonstrate a sophisticated strategy that allows hares to secure food by managing risk. They modify vigilance to correspond with current danger. When predators are abundant, predation is imminent, so hares must be most vigilant in places where predators are difficult to detect. When predators are scarce, risk declines, so hares are most vigilant in places where the hares are most visible to predators. Vigilance is only partially effective, so hares always eat less in dangerous places.