Bat social vocalizations are not well understood. Within a colony, bats often make squeaking sounds that people can easily hear and occasionally mistake for mice. While flying, bats sometimes produce social vocalizations that bear no resemblance to their normal search phase calls. This is often the case when bats are emerging from a roost site. These calls may communicate individual identity, social status, or territorial intentions. Of course, the bats may merely be humming to themselves because they are happy.

About the Recordings and Graphs

Each recording is a series of bat calls. The pitch (frequency) has been lowered by a factor of 16 so the calls fall within the range of human hearing. For example, a call that was originally 64 kHz is played back at 4 kHz. For most of the files, playback speed has not been altered, so you are hearing the calls at the speed they were produced. The social vocalizations of the Pallid bat have been slowed down so that you can hear the more complex nature of the call.

The graphs show the pitch (frequency) of the call versus time. Most of the graphs show frequency up to 80 kHz. The time scale has been compressed by removing all time between calls. If this were not done, only one or two calls would display on each graph. Hence, the duration of each call on the graph is accurate, but the time interval between calls is not shown. Since the wav files exactly match the corresponding graph, you can get a good feel for time by looking at the graph while playing the call.

• Pallid bat (Antrozous pallidus) (actual speed) 26 kb
• Pallid bat (Antrozous pallidus) (slow speed) 1.2 mb