Methods for radio tracking marine mammals in the open sea

Of all the groups of animals considered as subjects for a radio tracking study, marine mammals probably present the greatest challenge to the engineer and biologist. In addition to special packaging problems associated with operating in the ocean, the fact that marine mammals spend most of their time submerged essentially precludes transmitting at RF frequencies. During the past 36 months, a series of systems specifically for use on a variety of marine mammals in the open sea have been designed and tested under field conditions. This paper discusses the design of the radio transmitter and receiver system, frequency, power, packaging and antenna requirements, and discusses data on respiration rate, pattern and maximum depth of dive collected from several instrumented cetaceans.