Bats and echolocation Species identification Some species can be identified reliably from their echolocation calls using a bat detector others can be identified only in favourable situations, with considerable experience or by computer analysis. Echolocation calls are made to perceive the environment and the nature of the environment dictates the type of calls that are produced. This is in contrast to birdsong, which is a repetitive series of notes sung irrespective of the environment the bird is found in. For example, bats in open areas produce loud sounds, which travel far, whereas the same bat in cluttered areas produces quieter sounds so as not to be deafened by the echoes. Horseshoe bats can be identified from their unique echolocation calls, and the frequency of the call identifies the species. Pipistrelle bats have a unique echolocation call, which distinguishes them from other bat genera in the UK and the species of pipistrelle can be distinguished, although only under certain conditions. Identification of other species in the UK requires a combination of visual observation and listening to the sounds heard through the detector. There is some overlap in the echolocation calls of noctules, serotines and Leisler’s bat (although their calls are distinct from other UK species) but their size and wing shape can separate these species from each other. The identification of most Myotis species rests least with echolocation calls and comes mostly from the foraging style and environment in which the bat is found. The level of confidence of identification depends on the experience of the surveyor and the type of equipment used. The topic of identification of flying bats is complex and is covered in detail by Briggs & King, 1998. The use of time expansion techniques can help verify field identification of bats made with tuneable bat detectors. A detailed analysis of the echolocation calls of British bat species has been made by Vaughan et al. (1997).