A Harvard researcher reported in today's issue of Science magazine the first evidence of sex pheromones--chemical-scents that influence sexual behavior--in the bloodstream of a vertebrate.

David P. Crews, associate professor of Biology and Psychology, said yesterday he has found that female garter snakes hyperventilate during courtship, stretching their scales apart and releasing the blood-borne pheromones, which attract male garter snakes.

"This is a very unique form of communication--it has never been described for any other animal," he added.

Most pheromones are produced by glands and are released immediately into the environment, where they influence the behavior of other members of the species. By contrast, hormones, which are blood-borne, convey information from tissue to tissue within an individual organism.

Crews said the substance he found in garter snakes is transported like a hormone but eventually reaches the exterior and functions as a pheromone.

Garter snakes communicate primarily by way of pheromones, Crews said. The newly discovered pheromone conveys information about the female snake's reproductive potential.

"We are interested in exactly what information pheromones convey to other individuals within the species, and with how this method of communication evolved," Crews said.

He added that although this phenomenon may be unique to garter snakes, he hopes his discovery will spur similar research with other species. "For now, I will pursue my work with garter snakes," he said.

William R. Garstka, a graduate student in Biology, assisted Crews in his research and co-authored the Science article.