CORVALLIS - Zoologists at Oregon State University have taken a major step forward in their search for control strategies against the brown tree snake, a noxious reptile that threatens Pacific island ecosystems.
For the first time ever, at a university laboratory in Corvallis, Ore., the snake has mated in captivity.
The documentation of mating behavior will help scientists successfully identify sexual attractant "pheromones" in this snake species, which in turn could form the basis for a control or capture strategy.
In a separate advance, the OSU research program has also observed - again, for the first time ever - combat behavior among male brown tree snakes, which may lay the groundwork for discovering a repellant pheromone.
"This is a huge leap for our pheromone research program," said Robert Mason, an OSU assistant professor of zoology. "Now we have a fighting chance to accurately identify the attractant or repellant pheromones that could help us control this snake. We have a way to test the chemicals we isolate."
Brown tree snakes, which are native to Australia, were inadvertently imported to Guam years ago and devastated native wildlife populations there.
The snakes, voracious nighttime predators that can attack and eat almost any animal smaller than themselves, literally killed every bird on Guam and now swarm everywhere, to the tune of thousands of snakes per square mile.
As an avid hitchhiker on cargo planes and other transports, the snakes have many authorities terrified that they will continue their advance elsewhere - including Hawaii. Major efforts are under way to develop control or elimination strategies, but so far with very little success.
The OSU studies have ranged from laboratory pheromone research to scientists trekking the outback of Australia, tracking the brown tree snake to its ancestral roots. Only a good understanding of the snake's ecology, physiology and behavior will point the way to control, they say.
"In our most recent trip to Australia we identified a range of natural parasites that afflict brown tree snakes there, which are absent in Guam," Mason said. "We'll pursue ideas such as that if they seem productive."
Careful shipping regulations and snake-sniffing dogs are also being used to prevent spread of this reptilian pest, Mason said. But the pheromone research at OSU may be one of the most promising possibilities.
The idea, of course, would be to use these chemically-motivated influences on behavior to make the snake do what you wanted - go away, go a certain direction, or while seeking a mate, slither eagerly into a trap.
Scientifically, this task is easier said than done.
"There are literally thousands of chemicals in the lipid mixture on a brown tree snake's body," Mason said. "Only a few of them may be part of a sexual attractant pheromone. Our goal is to identify that pheromone, and stimulating these mating rituals can tell us when we're on the right track."
The courtship rituals now observed for the first time, Mason said, include chin rubbing, tongue flicking, males looping their tails under females, bodily "shudders" and other characteristics.
The key to producing courtship behavior, Mason said, was an improvement in mimicking the natural environment of the snake in a laboratory setting. What did the trick, he said, was a slight increase in the laboratory's daytime versus nighttime temperature differential.
The recent observation of male-to-male competitive behavior is also promising, said Mike Greene, an OSU doctoral student.
"This is a stylized form of combat, an intertwining and pushing that the male snakes do to establish dominance," Greene said. "This has never been seen before with this species, and it should open up a new avenue of research."
The OSU researchers hope that whichever snake wins the ritual combat then exudes a "superiority" pheromone that will repel male snakes. Using this concept - push the snakes one way, attract them another - may create a viable way to trap snakes. However, actual isolation and production of the various pheromones may still take several more years.
The OSU studies on this problem have been supported by the U.S. Fish and Wildlife Service, the Whitehall Foundation and the National Science Foundation through a Young Investigator Award.
"We don't think this approach will ever be a total solution to the problem of the brown tree snake," Mason said. "But it could be a tool to help control them, and an important one."
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