If you think your parents ever gave you the runaround, pity the baby Adelie penguins. Before a chick can chow on regurgitated krill, it must pursue its parents for up to half an hour. But parents are hardly shirking their chick-rearing duties: The comical chase, says a report in the current issue of Animal Behaviour, minimizes conflict between chicks, helping the weaker ones survive.
For decades, biologists have pondered why these curious feeding chases occur. "It looks like an old Charlie Chaplin movie," says the study's lead author, conservation biologist Dee Boersma of the University of Washington, Seattle. The adult penguins, she says, waddle up to a gaggle of unattended chicks and call to their young. The offspring immediately scramble after the beckoning parent "as fast as their little legs can carry them," says Boersma. The parent bolts, stopping after about 50 meters to feed a begging chick a partial meal, then flees again. Eventually the parent never looks back, plunging into the sea to fetch more food.
Some experts have suggested that the chases help parents ration limited food supplies. But that didn't make sense to Boersma: "If food was limited, you wouldn't want to come home and run your children around the dining room table," she says. Instead, Boersma guessed that the zigzag maneuvers would give the weaker chick a chance to get a beakful of krill without the stronger one on its tail. To test that idea, she and her colleague, Lloyd Davis of the University of Otago in New Zealand, observed interactions between parents and young on Ross Island in the Antarctic. Just as predicted, the chases increased the likelihood that the weaker chick got its share.
Experts say the study finally sheds light on one Antarctic mystery. "It's a behavior you can't help wonder about," says David Ainley, a marine ecologist at H.R. Harvey & Associates, an environmental consulting firm in San Jose, California. "There are certainly other questions to be asked," Ainley adds. For instance: Do parents feed chicks equally when food is scarce?