The bright colors and elaborate courtship displays of many male animals have long been interpreted as means of attracting females.

It ain't necessarily so, a biologist has found after studying one species of coral reef fish.

His observations in the waters off Panama's San Blas Islands show that females of the bluehead wrasse generally ignore the coloration and behavior of males and, instead, choose their mates after evaluating the features of the territory the male controls. In other words, the female bluehead wrasse picks her mate not for his looks or behavior but for the property he owns.

The discovery, reported by Robert R. Warner of the University of California at Santa Barbara in the October issue of the journal Animal Behavior, is one of few conducted in a way that distinguishes between the attractive value of the male and that of the territory he controls.

Warner's method was to swim, wearing scuba gear, into areas of the reef favored by wrasses and find a male occupying a territory. He watched as females swam through the area and males carried out what appeared to be courtship displays. Once a female made her choice, Warner captured and removed the male.

Although nearby males were in plain sight and put on "courtship displays," none could entice the female away from the territory. In a day or so, a nearby male would swim in and occupy the site. Typically, the female would mate with him.

Warner concludes that the males' colors and behaviors are probably used in competition with rival males contending for prime territories. The most favored territories were sharp ledges on the down-current side of the reef, where the prevailing currents would sweep the free-drifting eggs away from the reef and its predators.