for National Geographic News
Raging hormones might help explain why female emperor penguins that have lost a baby sometimes kidnap the chick of another.
This bizarre snatching behaviorseen briefly in the Oscar-winning movie March of the Penguinshas long puzzled scientists. (March of the Penguins was produced by National Geographic Features Films and Warner Independent Pictures.)
"The kidnapping lasts for a few hours or a week at most," said Olivier Chastel, a biologist at the French National Center for Scientific Research in Villiers en Bois.
After this time the seemingly distraught parent loses interest and abandons her stolen baby.
"The abandoned hungry chicks usually die from the cold or predation. There is no clear evolutionary advantage," he said. In other words the kidnapping practice doesn't seem to help chicks survive and therefore pass on their genes to the next generation.
But a new study indicates that a hormone that influences the penguins' parenting urges might be driving the birds to steal chicks (wallpaper: emperor penguin chicks).
The team's findings appear in this week's Journal of Experimental Biology.
When most birds incubate eggs, the females often produce high levels of prolactin, a hormone involved in parental behavior. The hormone levels drop if the birds' eggs are removed before they hatch.
But in emperor penguins the hormone levels remain elevated even after an egg is lost.
Chastel and his colleagues wondered if imbalances in the hormonedriven by the emperor penguins' unusual nesting ritualcould explain the kidnapping behavior.
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