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Mathematical Biology seminar
David Carrier
Biology Department, University of Utah
"The Face That Sunk the Essex: Potential Function of the Spermaceti Organ in Aggression"
October 8
3:05pm in LCB 225
Herman Melville?s fictional portrayal of the sinking of the Pequod was
inspired by instances in which large sperm whales sunk whaling ships
by ramming the ships with their heads. Observations of aggression in
species of the four major clades of cetaceans and the artiodactyl
outgroup suggest that head-butting during male-male aggression is a
basal behavior for cetaceans. We hypothesize that the ability of sperm
whales to destroy stout wooden ships, three to five times their body
mass, is a product of specialization for male-male
aggression. Specifically, we suggest that the greatly enlarged and
derived melon of sperm whales, the spermaceti organ, evolved as a
battering ram to injure an opponent. To address this hypothesis we
examined the correlation of relative melon size with the level of
sexual dimorphism in body size among species of cetaceans. We also
modeled impacts between two equal-sized sperm whales to determine if
it is physically possible for the spermaceti organ to function as an
effective battering ram. We found (1) that the evolution of relative
melon size in cetaceans is positively correlated with the evolution of
sexual dimorphism in body size, and (2) that the spermaceti organ of a
charging sperm whale has enough momentum to seriously injure an
opponent. These observations are consistent with the hypothesis that
the spermaceti organ has evolved to be a weapon used in male-male
aggression.
For more information contact J. Keener, 1-6089
E-mail:
keener@math.utah.edu
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