Acoustic systems with dual functions offer an interesting view into the evolution of animal communication systems. Bat echolocation has evolved primarily for orientation and foraging and these functions largely determine the acoustic parameters of echolocation calls. However, small variations in the parameters of echolocation calls, both within and between species, have the potential to encode species and individual identity, raising the possibility that echolocation calls also function in communication. 

Recent behavioural studies have demonstrated the ability of bats to discriminate between several different classes of individuals bases on echolocation call alone, supporting a communicative function for echolocation. Although call frequency appears to be the parameter most often used to discriminate between classes of individuals, there is evidence that other parameters, not yet identified, may also be implicated. Using a series of playback experiments on captive Horseshoe bats, I have teased apart individual components of echolocation to ascertain which components provide sufficient cues for discrimination between species. In addition to the frequency of the constant frequency component of the calls, duty cycle and the bandwidth of the initial and terminal frequency modulated components of calls exhibited individual signatures. Bats were able to use all of these parameters to discriminate between different classes of individuals, the most important of which will be discussed.
The role of echolocation in mate choice was also investigated using a two-alternative forced choice playback experiment. Bats were presented with different acoustic stimuli based on sex and body condition and observations were made of the preference shown towards each class of playback. Preference for playbacks of echolocation calls from the opposite sex or from individuals with a higher body condition was indicative of potential mate choice via echolocation.