Adaption
Why is this behavior important and how has it given the species a survival advantage in its environment?


Echolocation calls are distinct from social calls in both form and frequency. (Mark Denny, 2004)

Indeed, there is evidence that bats use their echolocation calls to navigate, as well as to detect and track prey. (Mark Denny, 2004)

Although Bats alter their transmitted sound in the presence of other bats (they also can make use of the calls made by other bats of the same species) , it isn’t known if they allocate frequencies cooperatively, or if individuals adjust their own calls to frequencies not in use in order to recognize their own echoes.(Mark Denny, 2004)

The finding that bats may regularly eavesdrop on calls from other bats supports the hypothesis that echolocation is important in communication as well as in biosonar. Densely packed communities of bats use species-specific frequencies that rarely overlap with other, often closely-related species. A hypothesis for this is that each species uses a ‘private bandwidth’ for acoustic communication. This suggests that echolocation can function as a badge of species identity. (Gareth Jones, 2007)

Bats use echolocation calls that are suited for foraging in particular habitats. Several species of bats are known to change their calls in predictable ways when they forage in different habitats. In addition to this, they varied from trial to trial in the same habitat. A flexible behavioral repertoire can increase success under varying conditions. (Matthew Wund, 2005)

Bats use echolocation for orientation during foraging and navigation. It also has a communicative form between roost members. They have been shown to react to echolocation calls with a complex repertoire of social behaviors. Bats adjust frequency of echolocation calls according to the presence of conspecifics, noisy environments, or habitat types. (Voigt-Heucke, 2010)

Sounds are generated in the larynx, which is larger than in other mammals. Air passing over the vocal chords makes them vibrate, and the muscles of the larynx are used to adjust tension, and change the frequency of the sound. The calls are emitted through the mouth or nostrils. The types of bats using nostrils usually have complex noseleaves (folds of skin or cartilage that act as an acoustic lens focusing the sound in front of the bat). Ears have large pinnae. The higher the frequency of the echolocation pulses, the smaller the eardrum, and smaller and lighter the ossicles so that they an vibrate more rapidly. Incoming sound vibrations push the eardrum, which pushes the ossicles, which vibrate the oval window, which are transmitted along inside the cochlea. The cochlea sifts and categorizes the sounds by frequency and send the information to the brain via the auditory nerve. Final processing happens in the auditory cortex. ( Altringham, 1998)

With the rules presented for CF and FM in mechanism, a bat adapts its ratio of use to its local environment.