Charlisartre was Right… it’s Testosterone’s Fault [ if you’re a booby…]
If you ever felt at least metaphorically like you wanted to kill your brother or sister, your sibling is lucky you’re not a booby. A Nazca booby, a Galpagos Island seabird, is eager and able to kill a sibling in the nest.
A new study links the murderous behavior to high levels of testosterone and other male hormones found in the hatchlings.
The elevated levels of male hormones, called androgens, increase aggression in both male and female chicks and prepare the birds to fight to the death as soon as they hatch, said David J. Anderson, professor of biology at Wake Forest University. “The older of two Nazca booby hatchlings unconditionally attacks and ejects the younger from the nest within days of hatching.”
The reason for this sibling spat: The parents of this species find it hard to raise more than one, so by wiping out the younger sibling, the older chick stands a better chance of surviving.
The bullying doesn’t stop in the nest. Surviving chicks frequently seek out nestlings in their colony, and during those visits they often bite and push around the defenseless youngsters, the researchers found.