When a bat detects a flying insect that it might want to eat, the search phase calls change to a feeding buzz. The calls become somewhat higher pitch, but most notably, they are produced so rapidly that the individual calls merge into what sounds like a buzz. This is best appreciated by looking at the graph and listening to the recording of a feeding buzz.

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 feeding buzz of the Mexican free-tailed bat has 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.

• Mexican free-tailed bat (Tadarida brasiliensis) (actual speed) 514 kb
• Mexican free-tailed bat (Tadarida brasiliensis) (slow speed) 4.4 mb