'Cycle of violence' seen in nesting birds

RALEIGH, N.C., Aug. 8 (UPI) -- Juvenile seabirds abused by older birds are more likely to grow up to become abusers themselves in a "cycle of violence," U.S. researchers say.

Researchers from Wake Forest University studying a colony of Nazca boobies in the eastern Pacific off of South America say chicks that are mistreated by older, non-related birds in turn grow up to be more violent toward younger birds.

The finding suggests that in wild animals, as in humans, "child abuse" can be passed on down generations.

"The cycle of violence effect may be a widespread cause of variation in the social behavior of vertebrates," biologist David Anderson told BBC Nature.

The seabird colonies are densely packed, the researchers said, which encourages episodes of violence.

There was a strong correlation between the frequency that Nazca booby chicks were attacked by non-breeding non-related adults and the incidence of them attacking chicks when they reached adulthood, the scientists said.

Being a victim of abuse raises levels of stress hormones, Anderson theorizes, and these levels may later trigger aggressive behavior in adulthood.