Satellite-Monitored Radio Tracking of Cetaceans: Developments in Transmitter Package and Attachment
Bruce R. Mate, Fisheries & Wildlife, Oregon State University, Hatfield Marine Science Center, Newport, Oregon 97365 USA, and Rod Mesecar, Oceanography, Oregon State University, Corvallis, Oregon 97330 USA
Our group has conducted satellite-monitored radio tracking of large whales (blues, humpbacks, grays, rights, and bowheads), dolphins (bottlenose, pilot whales, and white-sided), and manatees. We developed the packaging for all of the above and the attachments for the dolphins and whales. Our dolphin tracks (up to 107 days) and whale tracks (up to 85 days) have provided new information about migratory routes, reproductive range, and feeding areas (including substantial range extensions for several species). Many of these tags have collected data on dive depths, durations, water temperature, and time spent at the surface to reveal how the animals exploit their three-dimensional environment. We have additionally used satellite-derived sea surface temperature information to identify oceanographic features which whales may use (upwellings, eddies, and water-mass boundaries) to increase their foraging efficiency. Although we have had tags stay attached and run until their batteries were exhausted, we feel attachment mechanisms are the factor limiting the duration of most whale tracking experiments.
Our transmitters for large whales have evolved from a large, heavy device using sutures and applied by pole (1983) to a relatively small implantable dart applied by crossbow. Five basic attachment types have been used with several variations, but hydrodynamic drag, tissue "rejection," and physical contact (rubbing) are still issues that probably affect tag longevity. Dorsal fin attachments on dolphins are much more reliable because dolphins are small enough to capture, allowing controlled application on tissue that is stronger than whale blubber.
Because so very little is known about the movements, dive patterns, and behaviors of whales, even relatively short periods can reveal important aspects of whale behavior, habitat utilization, and migration. Tracking often provides a fundamental change in understanding where whales go or how they utilize their three-dimensional environment. Tag placement and deployment are critical to tag performance and longevity.
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