The influence of moonlight on the activity of little brown bats (Myotis lucifugus)

Lunar cycles influence the activity patterns of a variety of organisms including marine fish, rodents, birds, and fruit-eating bats. Lunar light, specifically a full moon, has also been suggested to depress the activity of insectivorous bats, because of increased predation risk or decreased insect prey abundance. These observations are generally anecdotal, however, with few quantitative data to support or refute them. The purpose of our study was to measure activity of little brown bats (Myotis lucifugus) in relation to the lunar cycle, and other environmental conditions, (e.g., ambient temperature, cloud cover, and wind strength). If bats are ''lunar phobic'' for predator avoidance reasons, then activity levels should decrease or shift to more sheltered habitats. We used ultrasonic bat detectors to assess bat activity. Counter to our prediction, the percent moon face illuminated did not significantly predict bat activity levels There was also no evidence of a habitat shift correlated with lunar light levels. Activity was significantly related only to ambient temperature, a result commonly found in other studies. Our results indicate that insectivorous bats are not lunar phobic, implying they do not experience substantially higher predation risk or lower prey availability during moonlit periods.