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No. 65: Sep-Oct 1989

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Why the hammer head?

Hammerhead shark
You probably thought, as we did, that the function of the hammerhead shark's weirdly shaped head was to separate the eyes and thus improve binocular vision. This is not the case. The visual fields of the hammerhead's eyes do not overlap at all. Each eye presents the brain with a separate, completely different image to integrate. What, then, could be the purpose of the hammer head? No one really knows, but three suggestions are as follows:

  1. The head acts as a hydrofoil and gives the heavier-than-water, swimbladderless shark better swimming control.

  2. Grooves on the hammer head channel water toward the nostrils, providing "stereoscopic sniffing."

  3. The head is a platform for electromagnetic sensors that help locate prey. Stingrays are a favorite food of the hammerhead, and the shark may de-tect them electromagnetically, as surmised by the author of this article in the following encounters:

    "I have observed great hammerheads swimming close to the bottom, swinging their heads in wide arcs (a motion common, in a lesser degree, to all large sharks) as if using the increased electroreceptive area of their hammer like the sensor plate of a metal detector. Sometimes, these animals would doubleback to scoop up one of several stingrays hiding in the bottom silt. The minute electrical pulse that keeps the stingray's heart and spiracles operating betrays their presence to a hungry hammerhead."

(Martin, Richard; "Why the Hammer Head?" Sea Frontiers, 35:142, 1989.)

From Science Frontiers #65, SEP-OCT 1989. 1989-2000 William R. Corliss

Science Frontiers Sourcebook Project Reviewed in:

Quotes

  • "A sourcebook of unexplained phenomena is therefore a valuable addition to a collection of scientific literature. William R. Corliss has provided this in the past with his source books of scientific anomalies in several subjects, and now he has provided it for astronomy. He has done an excellent job of collecting and editing a large amount of material, taken in part from scientific journals and in part from scientific reporting in the popular or semi-scientific press." -- "The Mysterious Universe: A Handbook of Astronomical Anomalies", reviwed by Thomas Gold, Cornell University, in Icarus, vol.41, 1980

  • "An interesting, systematic presentation of unusual weather [..] This book is recommended for a general audience" --"Corliss, William R., Tornados, Dark Days, Anomalous Precipitation, and Related Weather Phenomena, Sourcebook Project, 1983.", revieweed in Choice, September 1983
  • "..the science is necessarily somewhat speculative, but Corliss's symthesis is based on reputable sources." -- "Corliss, William R. (Compiler). Lightning, Auroras, Nocturnal Lights, and Related Luminous Phenomena" reviwed by Joseph M. Moran, Univ. of Wisconsin in Science Books and Films, Sep/Oct 1983

  • "Before opening the book, I set certain standards that a volume which treads into dangerous grounds grounds like this must meet. The author scrupulously met, or even exceeded those standards. Each phenomenon is exhaustively documented, with references to scientific journals [..] and extensive quotations" -- "Book Review: The moon and planets: a catalog of astronomical anomalies", The Sourcebook Project, 1985., Corliss, W. R., Journal of the Royal Astronomical Society of Canada, Vol. 81, no. 1 (1987), p. 24., 02/1987