Eclipsed: Emergence-return activity of two pteropodid bat species during lunar eclipse

Lunar eclipses are known to influence flight activity of tropical bats at foraging sites. However, little is known about the onset and offset of flight activity from the roost during lunar eclipses compared to other full moon nights. Emergence from and return to the roost were observed during a total lunar eclipse at a colony of the fruit bat Rousettus leschenaultii and during a partial lunar eclipse at a Pteropus giganteus colony in southern India. In addition, on the same partial eclipse night, a single male P. giganteus was tracked using GPS telemetry. Flight activity in both species was compared between the eclipse night and other full moon nights. In both cases, bats emerged before the eclipse and fewer R. leschenaultii individuals returned to the roost during the hours of the total eclipse, compared to the corresponding hours during other full moon nights. No such difference in return activity was observed in the P. giganteus colony or in the GPS tracked individual between the partial eclipse and other nights. This is the first attempt to study temporal flight activity of bats during lunar eclipses at their roosting sites. More roosting site observations, especially on species that roost in the open, are required to understand the effects of lunar eclipses on bat activity.