Radio Transmitter Tags
In recent years, radio transmitter tags have been developed for use on marine mammals. As they continue to become more reliable, these tags are expected to come into more and more widespread use.
Early radio tags ([Fig. A7]) were simple locator beacons which permitted the animal to be tracked by sending a signal to a tracking vessel or aircraft every time the animal surfaced and the antenna tip was exposed. Even these basic packages provide important information on movement, activity patterns, and respiration rates.
Subsequent developments have involved the addition of sensors to monitor the maximum depth of each dive and environmental parameters such as the water temperature at that depth ([Fig. A8]).
Logical extensions of these developments include the addition of numerous other sensors to permit simultaneous monitoring of multiple aspects of the animal's environment and the transmission of these data first to aircraft and subsequently to satellites for relay to shore-based laboratories.
In addition to permitting scientists to define movement patterns and daily diving patterns of cetaceans, the use of such devices offers an exciting means of determining the environmental parameters that trigger changes in their behavior.
Radio transmitter tags, in a variety of configurations, may be constructed and attached for short-term studies or for long-term monitoring of migrating animals. In either case, depending on their size and methods of attachment, radio transmitter tags may be visible on a free-swimming animal even at a considerable distance.