Echolocating bats use the echoes from their echolocation calls to perceive their
surroundings. The ability to use these continuously emitted calls, whose main
function is not communication, for recognition of individual conspecifics might
facilitate many of the social behaviours observed in bats. Several studies of
individual-specific information in echolocation calls found some evidence for
its existence but did not quantify or explain it. We used a direct paradigm to
show that greater mouse-eared bats (Myotis myotis) can easily
discriminate between individuals based on their echolocation calls and that they
can generalize their knowledge to discriminate new individuals that they were
not trained to recognize. We conclude that, despite their high variability,
broadband bat-echolocation calls contain individual-specific information that is
sufficient for recognition. An analysis of the call spectra showed that
formant-related features are suitable cues for individual recognition. As a
model for the bat's decision strategy, we trained nonlinear statistical
classifiers to reproduce the behaviour of the bats, namely to repeat correct and
incorrect decisions of the bats. The comparison of the bats with the model
strongly implies that the bats are using a prototype classification approach:
they learn the average call characteristics of individuals and use them as a
reference for classification
