References 229

of the signal within the heterodyne window. There are numerous electronic circuit designs and kits for bat detectors on the Internet. For example a simple kit is available from http://www.magenta2000.co.uk. A further example uses a piezoelectric transducer coupled to a simple heterodyne circuit is available from http://www.alanaecology.com. Circuit designs are also available for frequency division detectors, where the received frequency is divided by a factor (usually a power of 2) and output to a tape-recorder or headphones. Frequency division detectors tend to be less sensitive overall due to their broadband sensitivity to noise, and are less useful for listening in the field, but are useful for analysis if the signals are recorded to tape and analysed later.

Listening to bats using their echolocation calls while watching them catch prey and detect and avoid obstacles gives great insight into the potential for sonar orientation and navigation.

References

Fenton, M.B., 1995, Natural history and biosonar signals, In: Hearing by Bats (ed. A.N. Popper and R.R. Fay), pp37–86, Springer-Verlag, New York

Griffin, D., 1958, Listening in the Dark, Yale University Press

Grunwalf, J., Sch¨ornich, S., and Wiegrebe, L., 2004, Classification of natural textures in echolocation,

Proceedings of the National Academy of Sciences, Vol. 101, pp. 5670–5674

Møhl, B., 1988, Target detection by echolocating bats, In: Animal Sonar: Processes and Performance, (ed. P.E. Nachitgall and P.W.B. Moore), pp. 435–450, Plenum Press, New York

Morse, P.M., 1948, Vibration and Sound (2nd Ed.), McGraw-Hill, New York

Rossing, T.D., and Fletcher, N.H., 2004, Principles of vibration and sound (2nd Ed.), Springer-Verlag, New York

Saillant, P.A., Simmons, J.A., and Dear, S., 1993, A computational model of echo processing and acoustic imaging in frequency-modulated echolocating bats: The spectrogram correlation and transformation receiver, J. Acoustical Society of America, Vol. 94, pp. 2691–2712

Schnitzler, H.U., 1973, Control of Doppler shift compensation in the Greater Horseshoe Bat, Rhinolophus ferrumequinum, J. Comparative Physiology, Vol. 82, pp. 79–92

Schniztler, H.U., and Kalko, E.K.V., 2001, Echolocation by insect-eating bats, Bioscience, Vol. 51, No. 7, pp. 557–569

Schnitzler, H.U., Moss, C.F., and Denzinger, A., 2003, From spatial orientation to food acquisition in echolocating bats, Trends in Ecology and Evolution, Vol. 18, pp. 386–394

Stein, B.E., and Meredith, M.A., 1993, The merging of the senses, MIT Press, Cambridge, Mass. USA Waters, D.A., and Jones, G., 1995, Echolocation call structure and intensity in five species of insectivorous

bats, J. Experimental Biology, Vol. 198, pp. 475–489

Waters, D.A., Rydell, J., and Jones, G., 1995, Echolocation call design and limits on prey size: a case study using the aerial-hawking bat Nyctalus leisleri, Behavioural Ecology and Sociobiology, Vol. 17, pp. 312–328

Wells P.N.T., 1969, Physical principles of ultrasonic diagnosis, Academic Press

Resources

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