(…) Although various sensory mechanisms are present in cetaceans, special navigational problems occur when animals are in a pelagic environment which can minimize available cues. Dawbin (1966) has observed that the migration routes of humpback whales cannot be consistently related to bottom topography, direction of ocean currents, or the nature of water masses. There are few distinctive surface features and the bottom topography is frequently too distant to provide precise cues. During overcast conditions, celestial features are unavailable. In an ocean environment of limited navigational cues, the earth’s magnetic field could provide necessary information for orientation. There is evidence that a number of marine vertebrates can detect magnetic fields (Walker et 01., Chapter 20, this volume). Recently, Klinowska (in press) has reported evidence that cetacean strandings in the United Kingdom all occur at areas of minimum magnetic field. This evidence has important implications for the ability of cetaceans to use magnetic fields and use them to guide migrations.
Our own research on magnetic detection by cetaceans followed two tracks. In our behavioral studies, we took a preliminary look at the relationship of geomagnetic events with cetacean strandings and migrations, but concentrated our efforts on a variety of conditioning experiments to investigate magnetic perceptual abilities in two bottlenose dolphins, Tursiops truncatus. In our anatomical studies, we looked for a potential magnetic receptor in a diverse group of subjects, four odontocetes and a mysticete: two species of dolphins, the common dolphin (D. delphis), a pelagic animal, and the bottlenose dolphin (T. truncatus), a coastal species; Cuvier’s beaked whale, Ziphius cavirostris, a large, deepwater species; Dall’s porpoise, Phocoenoides dalli, a coastal animal; and a humpback whale, Megaptera novaeangliae, the only mysticete studied. (…)