Sibling bullying doesn’t cause lasting wimpiness

A study of blue-footed boobies found that while siblings bully each other badly in the nest, the youngsters grow into adults with normal levels of aggression. Flickr

Harsh sibling bullying maybe tough to endure as a youngster but victims won’t necessarily grow into cowed and meek adults, a study on birds has found.

Mexican researchers studying blue-footed boobies, which usually produce two chicks per nest, observed that one chick usually dominated the other, subjecting its sibling to violent pecks and bites and eating the majority of available food.

The victim may develop submissive qualities while in the nest but will not carry wimpy attributes into adulthood, they found.

“Former junior and senior chicks of the blue-footed booby, whose typical brood of two chicks exhibits a consistent dominance–subordination relationship with strong ‘trained winner’ and ‘trained loser’ conditioning effects, did not differ in their aggressiveness while defending their nest against a conspecific intruder stimulus,” said the paper, which was published in the journal Biology Letters.

“Our results suggest that aggressive subordination and associated food deprivation, poor growth and elevated stress hormone during infancy do not prejudice aggressiveness of adult boobies during at least the first 13 years of life.”

The finding contradicts a view widely held among psychologists that victims of sibling bullying may carry submissive qualities into adulthood.

“In nature, the development of aggressiveness and competitiveness in vertebrate infants, including those that grow up in dominance hierarchies, may be more resilient to aggressive subordination and low status than biologists and psychologists usually assume,” the researchers said.