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Science Frontiers ONLINE No. 53: Sep-Oct 1987 |
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Magnetic "dead" reckoning
Try on this theory for size. Whales subconsciously strand and kill themselves in order to maintain their populations at optimum levels! Well, the dozen or so other theories that have been advanced to account for whale strandings haven't been much better.
M. Klinowska thinks that she has some clues indicating a better theory. First, all whale strandings (in Britain, at least) occur where magnetic field contours are perpendicular to the shoreline. Second, strandings are also correlated with irregular changes in the magnetic field. You will see the significance of these facts after you hear her theory.
"Cetaceans use the total geomagnetic field of the Earth as a map. A timer, also based on this field, allows them to monitor their position and progress on the map. They are not using the directional information of the Earth's field, as we do with our compasses, but small relative differences in the total local field. I arrived at this explanation after a detailed analysis of the records of strandings in Britain, but it has so far been confirmed by two groups working in the U.S. Similar work is in progress in other parts of the world."The total magnetic field of the Earth is not uniform. It is distorted by the underlying geology, forming a topography of magnetic 'hills and valleys.' My analysis shows that the animals move along the contours of these magnetic slopes, and that in certain circumstances this can lead them to strand themselves. In the oceans, sea-floor spreading has produced a set of almost parallel hills and valleys. Whales could use these as undersea motorways, but might swim into problems when they came near the shore, because the magnetic contours do not stop at the beach. They continue onto the land, and sometimes so do the whales."
In addition to stranding because of land-intersecting contours, unpredictable changes in the earth's magnetic field can upset the whales' timing mechanism, causing them to lose their true position on their magnetic dead-reckoning maps. Magnetically speaking, they become lost.
(Klinowska, Margaret; "No Through Road for the Misguided Whale," New Scientist, p. 46, February 12, 1987. Also: Ellis, Richard; "Why Do Whales Strand?" Oceans, 20:24, June 1987.)
Comment. Klinowska's theory is attractive in the sense that one can test it by checking strandings against magnetic contours and magnetic variations. However, the theory requires whales to sense changes in the earth's field of only 1 nanotesla (that is, one part in 50,000). No one has any idea how this can be accomplished biologically. Furthermore, how are the world-wide magnetic reference maps constructed and stored in the whales' brains?