Abstract:
We investigated the acoustical component of the recognition process leading to successful motherepup
reunions in the greater sac-winged bat, Saccopteryx bilineata, using both a statistical approach and playback
experiments. Statistical evidence for individual distinctiveness was found in the isolation calls uttered by
pups and, to a weaker degree, in the echolocation pulse trains emitted by mothers. In contrast to other bat
species, isolation calls of S. bilineata pups were complex and multisyllabic, with most of the vocal signature
information encoded in the composite syllables at the end of calls. Playback experiments with free-living
bats revealed that mothers were able to discriminate between their own pup and an alien young on the
basis of isolation calls alone, which confirms the results of the acoustical analysis on vocal signatures in
isolation calls. Pups, on the other hand, indiscriminately vocalized in response to echolocation pulse trains
from their own and alien mothers, rendering the motherepup recognition process unidirectional. The
one-sidedness of the vocal recognition process in S. bilineata as well as in other bat species might be explained
by a lack of selection pressures that shape mutual vocal parenteoffspring recognition in other species
of mammals and birds. To our knowledge, this study is the first in which playbacks were used to elicit
antiphonal calling behaviour between bat mothers and pups experimentally. We argue that vocal responses
to playback stimuli are a more feasible and reliable response measure for conducting mothere
pup recognition playbacks in bats than the phonotaxis behaviour used in the past.
