Parenthood can be a struggle, particularly for families with multiple children in need of care, nurturing, protection and attention. But a weary mom or dad may find solace in the reassurance that all parents with several offspring face a similar challenge — even the non-human variety.
Researchers at the University of Washington wanted to know how Magellanic penguin parents in South America balance the dietary demands of multiple chicks. As they report in a paperpublished Jan. 23 in the journal Animal Behaviour, when a Magellanic penguin parent returns to its nest with fish, the parent tries to feed each of its two chicks equal portions of food, regardless of the youngsters’ differences in age or size.
This finding surprised the team, since parents across the animal kingdom, including other penguin species, often allocate resources unequally to their chicks based on factors like offspring age, body condition, health and behavior, said senior author P. Dee Boersma. Boersma, a UW professor of biology and director of the Center for Ecosystem Sentinels, has for more than three decades studied penguins at Punta Tombo, a coastal region in Argentina that hosts one of this species’ largest breeding colonies.
“This is an exciting finding because, among animals, it is very unusual for parents to divide food equally among their offspring,” said Boersma. “This makes Magellanic penguin parents stand out not just among penguins, but also animals in general.”
Magellanic chicks are the same size when they hatch, but eggs within a nest hatch at different times. After mating, a Magellanic female lays two eggs about four days apart. One chick typically hatches at least two days before the other. Chicks grow to different sizes based on the timing of their first feedings. By the time both chicks are at least 20 days old, one chick is on average 22 percent heavier than its sibling, the team found. Yet despite these size differences, this study shows that when Magellanic chicks are older and more mobile, parents feed both chicks equally as well as rapidly.
“These findings raise some very interesting evolutionary questions about how and why this behavior — feeding chicks equally — arose,” said Boersma.
Read the original article by James Urton on UW News.