Mortality by moonlight: predation risk and the snowshoe hare.

Optimal behavior theory suggests that prey animals will reduce activity during intermittent periods when elevated predation risk outweighs the fitness benefits of activity. Specifically, the predation risk allocation hypothesis predicts that prey activity should decrease dramatically at times of high predation risk if there is high temporal variation in predation risk but should remain relatively uniform when temporal variation in predation risk is low. To test these predictions we examined the seasonably variable response of snowshoe hares to moonlight and predation risk. Unlike studies finding uniform avoidance of moonlight in small mammals, we find that moonlight avoidance is seasonal and corresponds to seasonal variation in moonlight intensity. We radio-collared 177 wild snowshoe hares to estimate predation rates as a measure of risk and used movement distances from a sample of those animals as a measure of activity. In the snowy season, 5-day periods around full moons had 2.5 times more predation than around new moons, but that ratio of the increased predation rate was only 1.8 in the snow-free season. There was no significant increase in use of habitats with more hiding cover during full moons. Snowshoe hares' nightly movement distances decreased during high-risk full-moon periods in the snowy season but did not change according to moon phase in the snow-free season. These results are consistent with the predation risk allocation hypothesis. [ABSTRACT FROM AUTHOR]

Copyright of Behavioral Ecology is the property of Oxford University Press / USA and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)