Ontogeny of vocal signals in the little brown bat,Myotis lucifugus

Abstract

This study reports developmental changes in the vocal signals produced by wild-caught pre-volant and volantMyotis lucifugusAudio recordings were made from young animals (1–33 days old) and adults (over 1 year of age). The animals were removed from an attic maternity roost and studied individually in a room below. To stimulate flight-related behaviours, animals were released from a launching platform via a hinged floor, and their vocalizations were recorded as they approached a soft foam pad below. When the hinged floor opened, the youngest animals (1–4 days old) typically dropped onto the pad, but older animals either flapped their wings to achieve some horizontal displacement (>4 days) or sustained horizontal flight (>17 days). Vocalizations recorded under these conditions showed frequency modulation characteristic of adult echolocation sounds, even in animals as young as 4 days. Ontogenetic trends showed an increase in sound frequency, an increase in sound repetition rate and a decrease in sound duration as the animals matured. These data are discussed in the context of the development of echolocation behaviour in bats.