Nazca Boobies on the Galapagos Islands leave their chicks to forage for food. During this time, other adults may approach unrelated chicks and their conduct may be aggressive or sexual in nature. After studying these birds over three breeding seasons, David Anderson (Wake Forest University) and his colleagues observed that the chicks that had experienced this conduct grew into adults that engaged in the same kind of behavior to other chicks. And, in fact, they found high correlations between the amount of aggressive behavior demonstrated by the adults and the amount of abuse they had endured as nestlings. The observers who assessed the behavior of these adults were unaware of the experiences of those birds as chicks; they didn't know that these birds had themselves been the victims of "bullying."
A BBC Nature article about this research quoted Dr. Anderson as saying, "The link we found indicates that nestling experience, and not genetics, influences adult behaviour." He suspects that being a victim of abuse raises levels of stress hormones, and these hormonal levels later trigger aggressive behaviour, completing the cycle of violence.
The New York Times carried a feature about this paper on 10 October 2011: http://www.nytimes.c...r=1&ref=science
The full text of the paper has been made available courtesy of UC Press for a limited time:
and subsequently will be available in The Auk 128:4 (coming this fall).