420 MECHANICAL AND ACOUSTICAL SENSES 



INTRODUCTION 



Recent advances in acoustic and radio telemetry have made these techniques 

 increasingly useful to biologists conducting field studies of the behavior 

 patterns and underlying sensory mechanisms of terrestrial and marine 

 animals. In the case of free-ranging sharks, especially the larger active species, 

 telemetering techniques are particularly needed because of the difficulty of 

 studying these animals by direct underwater observation. Such difficulties 

 stem from sharks being generally (1 ) shy of divers unless attracted by bait, 

 (2) wide ranging, and (3) in a concealing environment, i.e., visibility a small 

 fraction of home-range dimensions. In addition, many species are usually too 

 deep for scuba observation, and most species are active primarily at night. 

 There is also a significant danger to the unprotected observer in certain 

 circumstances, e.g., agonistic attack by gray reef sharks (Johnson and Nelson 

 1973). 



This review is intended primarily for biologists contemplating the use of 

 telemetry in field studies of sharks or other large marine animals. Present 

 capabilities and future possibilities are discussed, with example taken mainly 

 from shark-telemetry studies in which the author has been involved. This 

 paper is based partly on and includes some modified excerpts from the 

 previous article "Ultrasonic Telemetry of Shark Behavior" (Nelson 1974). 



The main emphasis is on ultrasonic telemetry, as only acoustic trans- 

 mission is practical from fully submerged, free-ranging sharks in seawater. 

 Radio telemetry is considered, however, for the special application of non- 

 continuous trackings using timed-release radio floats. Such radio methods 

 appear most useful for monitoring relatively long-term movements or migra- 

 tions. 



For a broad coverage of the techniques of telemetry in biological research, 

 the reader is referred to the second edition of Bio-medical Telemetry 

 (Mackay 1970). Although written prior to some of the current electronic 

 technology (e.g., CMOS micropower digital integrated circuits), the book 

 contains a wealth of information, ideas, and circuits and should be con- 

 sidered a primary reference work for those involved with biotelemetry. 

 Mackay's emphasis is on radio methods, such as low-power transmission of 

 physiological data from inside the body to outside, but both long-range field 

 applications and ultrasonic methods are treated. The reader is also referred 

 to the "Underwater Telemetry Newsletter" 1 for up-to-date, practical infor- 

 mation on the telemetering techniques (mainly ultrasonic) used in tracking 

 and monitoring aquatic animals. Each issue also contains news of biological 

 studies and a bibliographic updating of publications in underwater bio- 

 telemetry. An annotated form of this bibliography is available elsewhere 

 (Stasko 1975), as well as a more recent review of the subject (Stasko and 

 Pincock 1977). 



^''Underwater Telemetry Newsletter" is presently edited by Charles C. Coutant, Envi- 

 ronmental Sciences Division, Oak Ridge National Laboratory, P.O. Box X, Oak Ridge, 

 Tennessee 37830. It has been distributed to interested researchers approximately 

 twice a year since 1971. 



