November 2018, ScientificAmerican.com 17ANIMAL BEHAVIORUnwanted
Advances
Female cockroaches gather in
groups to avoid male attentionHumans are not the only species that deals
with harassment. According to new research,
female cockroaches may cluster together to
keep male suitors at bay.
Christina Stanley, an animal behavior lec-
turer at the University of Chester in England,
D³lxß̧§§xDøxäÇøî0DUxxî§x ̧¦- roaches in special containers to observe their social behavior. The roaches would gather in primarily female groups and jostle out the males. “Female [roaches] created this better social environment by excluding the males,” says Stanley, who led the study published online in July in Ethology. Because the females are much larger than the males, they “are more dominant, so they are more able to push the males out of the way,” she adds. The researchers also ran an experiment with a higher ratio of male to female roaches. Under this condition, the females received more approaches and antenna investigations from males intent on mating. Thus, the
xD§xäî ̧¦DäDäîßDîxāî ̧lxxî males’ advances, Stanley says. Coby Schal, an entomology professor at North Carolina State University, who was not involved in the research, is uncon vinced that the females were all trying to avoid male Dîîx³î ̧³çxäDāäîxäąxlxßx³xUxîÿxx³
the sexes alone could account for the males
getting kicked out.
But the changed behavior in the experi-
ment with the excess males shows that more
äDîǧDāj3îD³§xāäDāäÍ §ä ̧j
xD§x0D
beetle roaches can store sperm from a single
mating. Therefore, any further copulation
would waste energy and could result in injury
(not uncommon among roaches). Beyond
brief time windows for initial encounters, the
otherwise social females appear to have little
JOEL SARTORE use for males. — Joshua Rapp Learn
Getty Images
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