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Female fish fond of male's fiefdom.

Female fish fond of male's fiefdom

To the female bluehead wrasse, it's not the brilliant coloration or amorous displays that make a male most desirable, but rather his real estate holdings.

Females of this coral-reef species appear more concerned with where they mate during their daily spawning than with whom, according to Robert R. Warner, a biologist at the University of California at Santa Barbara. In Warner's study of reefs in the San Blas islands off Panama, the most coveted spawning sites are those where the current sweeps eggs away from the reef and its predators. The males who control these sites are most likely to mate.

According to behavioral ecologist Luther Brown at George Mason University in Fairfax, Va., Warner's study is one of a very few that have been able to unequivocally separate the appeal of a male animal's appearance and behavior from that of his territory. Warner was able to do this experimentally by removing dominant male wrasses from their territories and noting the reactions of the female fish. He found that the females remained loyal to specific spawning sites even after new males from elsewhere in the reef took over the newly vacated spots. This loyalty was demonstrated most strongly in two cases, in which females stayed at one site after the resident male moved into an adjacent site that was in plain view of his old territory, writes Warner in the October ANIMAL BEHAVIOR.

According to Warner, behavioral biologists have long assumed that coloration and courtship in male animals indicate that females judge these qualities in choosing their mates. "These studies have begun to show that we shouldn't jump to that conclusion with every species,' he says.

But if female wrasses largely ignore coloration and courtship, why have these qualities evolved in male wrasses? That's the subject of Warner's next research. For now, he speculates that bright coloration may play a part in battles between males for sites. Courtship displays may signal to females that there are no predators lurking about and it is safe to spawn.
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Author:Weisburd, Stefi
Publication:Science News
Date:Nov 7, 1987
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