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Not Too Large, Not Too Small, but Spoiling for a Fight
Andrew HurlyTwo male giant hissing cockroaches (Gromphadorhina portentosa) squaring off.
By SINDYA N. BHANOO
Published: December 22, 2010
Male hissing cockroaches in Madagascar are aggressive creatures that ram one another’s heads and flip one another over. They can also flick their abdomens to forcefully whack another male.
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Get Science News From The New York Times » Certain individuals, though, are more aggressive than others. Now, researchers report that the level of aggressiveness is correlated to body size.
Males that are either small or large tend to display less aggression than those that are medium-size, according to the research, published in The American Naturalist.
“I had this idea that maybe if you’re big you’re going to win all your fights anyway,” said David Logue, a behavioral ecologist at the University of Puerto Rico and the study’s lead author. “And I wondered who would get the greatest benefits from being aggressive.”
It turned out that aggression is most valuable to medium-size cockroaches, since they have the most to lose and gain, Dr. Logue said.
He and his colleagues tested their hypothesis by stroking 70 male cockroaches with the antennae of another male cockroach. The cockroaches sensed the chemical emission from the antennae, and responded to it.
Interestingly, the cockroaches responded more aggressively to antennae taken from smaller males, and less aggressively to antennae from larger males.
The researchers also staged fights between cockroaches and created a computer simulation to confirm that midsize cockroaches are the most aggressive.
Although the cockroaches don’t seriously injure one another in their fights, their battles seem to be over territory.
Females tend to congregate in certain areas, and males fight to stay in these spots for maximum succ