The pallid bat's echolocation calls sound like this. In more open areas, the bat switches to calls of longer duration and lower frequency, sometimes as low as 12 kilohertz that are audible to humans. In many cases, call intensity is related to a bat's feeding habitat. Bats that feed in open areas produce the loudest calls. The following echolocation calls from a big brown bat were recorded as the animal hunted in a relatively open desert habitat.
Bats can tailor their echolocation calls to many different conditions.
These are most often used when bats are flying in groups where they need to avoid collisions. The following recordings were taken as a colony of Mexican free-tailed bats left their roost under a highway bridge in Tucson, Arizona. Bats also use a wide range of vocalizations to communicate. Many of these contain ultrasonic components that are above our range of hearing. These recordings are slowed down and repeated.