Geomagnetic Orientation in Cetaceans: Behavioural Evidence
Cetaceans appear to use the flux density of the earth’s magnetic field (total field) in two ways as an aid to travel. The topography of the local field is used as a map, with the animals generally moving parallel to the contours. A timer, based on the regular fluctuations in this field, allows the animals to monitor position and progress on this map. Problems can arise leading to live strandings when the geomagnetic contour routes cross land or when the pattern of time information is disrupted by irregular field fluctuations. The animals do not use directional geomagnetic information, for example as we do with our magnetic compasses.
Statistical evidence for this travel strategy has come from the positions and timing of live strandings around the UK coast, and from similar studies elsewhere. Other sources of information on cetacean behaviour are being explored in order to gain further insights into this travel strategy. Among these are the records of the drive fisheries for pilot whales (Globicephala melas) in the North Atlantic. Traditional driving beaches generally have the same characteristic geomagnetic topography as live stranding sites, and it therefore appears that the whalers are exploiting the normal orientation strategy of the animals to facilitate their work. These whales will flee without reference to geomagnetic contour routes when alarmed — perhaps another means whereby the animals can take the “wrong turnings” which may lead to live strandings. Since they can be driven by experienced crews without reference to the geomagnetic contour route, this method could be used for averting live strandings or for rescue purposes. However, it is unlikely to be practical today, because of the lack of experienced driving crews.
KeywordsFaroe Island Harbour Porpoise Magnetic Compass British Geological Survey Pilot Whale
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