Effect of moonlight on the foraging behaviour of a Megachiropteran bat Cynopterus sphinx

Abstract

We studied the influence of moonlight upon the foraging activity pattern of the fruit bat Cynopterus sphinx. We observed the bats when foraging on the fruits of Calophyllum inophyllum and on the leaves of Mimusops elengi and Cassia fistula for 31, 27 and 28 days, respectively at the botanical garden in the Madurai Kamaraj University campus. The number of feeding bouts was recorded every hour between 18:00 and 05:00. A feeding bout involves a bat landing on the tree and collecting a part (or whole) of the fruit or a leaf. The total number of feeding bouts was negatively correlated with per cent moonlight each night. The number of feeding bouts decreased during the waxing phases of the moon. During the period of new moon the mean number of feeding bouts was significantly higher compared to the periods of other phases. During the first quarter and the last quarter phases, feeding occurred more during the dark part of the night, especially when the bats foraged upon M. elengi and C. fistula. While cloud cover enhanced the foraging activity, lightning and thunder suppressed it. Our study indicates that moonlight influences the foraging activity of C. sphinx.