Snowshoe hares are more vigilant when feeding in the safety of dense shrubs than they are in risky open habitat

Risk management isn’t only for the financial world; animals in the wild are constantly balancing risk and reward.

Is energy gained by feeding in an open and unprotected area worth the risk of predation? Can vigilance be reduced when prey use habitats that allow escape from predators?

We answered these questions by testing theory that predicts how animals should manage the risks of being killed by predators.

We chose snowshoe hares in northern Ontario for these tests because:

(1) they live under a high risk of being killed by Canada lynx and other predators,

(2) their behaviour is easily photographed by motion-detecting cameras while they travel and feed along snow-packed runways,

(3) they look for food as individuals,

(4) they forage eagerly on small jack-pine boughs stuck in the snow, and

(5) they forage in the apparent safety of dense alder shrubs as well as in putatively risky open areas.

We assessed their risk management by analyzing the size of pine boughs that hares leave behind after their nighttime feeding as well as the proportion of camera images that revealed vigilant (e.g., erect or standing posture) behaviour.

Surprisingly, hares were more vigilant in alder habitat that they use to hide from and evade predators than they were in the open along abandoned logging trails (i.e., runways).

The paradox of increased vigilance in alder emerges because dense branches obstruct their field of view and ability to see predators. Predators are more visible in the open so hares can be less vigilant there.

Hares trade-off the safety afforded by numerous escape routes in the shrubs with the requirement to increase vigilance to detect predators concealed by vegetation.

The trade-off reduces feeding efficiency in alder and equalizes the risk with foraging in the open as long as foraging opportunities are close to alder. Hares are more vigilant and forage less in the open when food is located farther from the safe alder habitat.

The results demonstrate the sophisticated ability of prey species to manage risk and reveal unforeseen costs that may accrue to wildlife when humans modify habitat.

Read the full paper — Trade-offs between sight lines and escape habitat determine spatial strategies of risk management by a keystone herbivore by Douglas W. Morris and Sundararaj Vijayana.