Bat Echolocation Research tools, techniques and analysis

Abstract

(Uploaded by Plazi for the Bat Literature Project) In Europe, ultrasound detectors are used to conduct various types of fieldwork on bats, including ecological research, area surveys, and monitoring of populations. The heterodyne system has been used extensively during the last 25 years and is still the most common. To enable the recording of information about frequencies, the frequency-division system was commonly used in Europe, singly or in combination with heterodyne. In 1985, time expansion became available, and this system is now widely used in combination with the heterodyne system for identifying bat species in the field. In this paper, I assess the utility and limitations of the heterodyne and timeexpansion systems using examples from work on the European bat fauna. The advantage of the two systems in combination is improved detection of bats, instant identification of species, and the ability to subsequently analyze recordings. Further, I illustrate the importance of sampling species-specific sequences and being aware of various limitations and pitfalls. Even the most skilled observers need to accept that it is not always possible to identify species. Separating similar species often requires long periods of observation during which bats can be heard (and seen) hunting or performing characteristic behaviors. Therefore, in many studies, some species must be pooled into groups, e.g., using line transects when there is limited time for each observation.