Anatomy of Bats

As the only flying mammals, bats have unique anatomy even without considering echolocation.  Most species weigh less than 50 grams as adults, allowing them great mobility and a diverse range of niches to exploit (Fenton 1997).

All terrestrial mammals vocalize using the same respiratory and laryngeal muscles. Vocalizations require the coordinated movement of jaw, lips, and tongue for shaping the acoustic properties of voice (Smotherman 2007).

Bats only have small variations from normal mammalian laryngeal anatomy. Laryngeal cartilage may contain additional ossification or calcification for scaffolding. Bats also have subglottic laryngeal cavities that may function as air sacs. All calls originate in the larynx and are transmitted through the nose or mouth (Fenzl and Schuller 2007)

Image used with permission from Lollar

All bats are characterized by forelimbs that have been adapted for flight.

Prior to molecular studies, morphological data was used in bat systematics. Laryngeal echolocation and presence/absence of premaxillary bones were used to distinguish suborders of bats (Jones and Teeling 2006).

Image used with permission from Lollar

A comparison of thoracic structure in bats using laryngeal echolocation showed significant modifications beyond those involved with flight. Bats that use low duty cycle echolocation also differ significantly in thoracic morphology from those that use high duty cycle echolocation. Muscles recruited in low duty cycle signals may be poorly developed in high duty cycle echolocators (DesRoche et al. 2007)

Two different bats with the same type of CF-FM call use different anatomical structures to create similar vocalizations. The horseshoe bat emits a call through its nose, while the mustached bat calls through its mouth (Smotherman 2007).

Anatomical converegence can also play a role in detecting vocalizations. Megadermatidae and Nycteridae are two bat species that are not very closely related. Both inhabit similar environments, and have evolved large ears to detect prey-generated sounds in cluttered siutations. They also exhibit elaborate nose-leaves and similar call design (Jones and Holderied 2007).

The wing of a Miniopterus australis. Photo courtesy of Laura Street.