Overview of Echolocation

What is echolocation?

Echolocation is an active sensing system, in which animals use the difference between what they hear and what they say to learn about the surrounding environment (Fenton 2003).

What is an active sensing system?

The use of self-generated energy to probe the environment.  Various animals make use of active sensing systems including bats, dolphins, electric fish, and rodents.  Although these systems differ, all share some characteristics.  The return signal must be strong enough to be detected by the sensory receptors, and the signal must propagate faster than the organism moving through the environment.  The probe cannot reveal the animal to either prey or predators.  Metabolic costs of signal production factor into the sensing system, and sensory and motor capabilities must be integrated in the nervous system (Nelson and MacIver 2006).

Image used with permission from Lollar

When is echolocation not useful?

When many bats are flying and echolocating in the same area, a situation known as the cocktail party effect arises. This situation is named after the ability of people to be in a room full of voices, and to concentrate on only one. Bats must be able to separate and group sounds from many sources into constituent objects. Spatial memory is thought to play a major role in situations such as mass exodus from a cave. Anecdotal evidence supports this theory: when bat caves were blocked off by doors, thousands of bats were found dead upon colliding with the door. Clearly they were capable of detecting such as obstacle, but were choosing to rely on memory instead (Ulanovsky and Moss 2008)

Do bats use echolocation for social communication?

Bats use different calls for communication and navigation.  For communication calls, bats determine information content themselves. In echolocation, signal parameters depend on environment and may shift depending on location (Fenzl and Schuller 2007)

Horseshoe bat. Photo courtesy of Kelly Cloward.