Localization of prey by the Indian false vampire bat Megaderma lyra

Studies on gleaning bats indicate that they do not mainly rely on echolocat ion to detect and capture prey from surfaces. In the event of not using ech olocation, there may be an error in their passive localization of prey comp ared to the bats which use echolocation. It is to be tested whether the amo unt of such error is related with the size of the prey in the passive local ization employed by gleaning bats. We conducted experiments on the Indian f alse vampire bat Megaderma lyra in an outdoor enclosure using small, medium and large-sized frogs as prey. M. lyra captured live and freshly killed fr ogs only when they jumped or when pulled with a long thread on a sandy floo r. Bats were more successful in capturing frogs without error (i.e. landing straight on the frog) under the background of fluorescent light than red l ight. The number of captures of live frogs without error was also significa ntly higher compared to the captures of freshly killed frogs under both the lights, except with the large-sized frogs. The number of jumps made by the live frogs decreased with their body lengths increased before M. lyra capt ured them without error. In a few observations, instead of landing straight on the frogs the bats landed on the floor close to the frogs and then capt ured them in a short jump (i.e. localization made with an error). The dista nce between the final position of the frogs and the site at which the bats landed on the floor prior to the capture, is considered as the amount of er ror committed by bats. While the bats localized and captured the frogs with an error, we found a linear decrease of error with an increase in the body length of the frogs. Bats never responded to the movements of tiny live an d dead frogs of 0.8-1.3 cm.