Physiology: Animal Function and Reproduction


What is unusual about the way the emperor penguin’s eggs are incubated?

Each female emperor penguin (Aptenodytes forsteri) lays one large egg. Initially, both sexes share in incubating the egg by carrying it on his or her feet covered with a fold of skin. After a few days of passing the egg back and forth, the female leaves to feed in the open water of the Arctic Ocean. Balancing their eggs on their feet, the male penguins shuffle about the rookery, periodically huddling together for warmth during blizzards and frigid weather. If an egg is inadvertently orphaned, a male with no egg will quickly adopt it. Two months after the female’s departure, the chick hatches. The male feeds it with a milky substance he regurgitates until the female returns. Now padded with blubber, the females take over feeding the chicks with fish they have stored in their crops. The females do not return to their mate (and own offspring) but wander from male to male until one allows her to take his chick. It is then the males’ turn to feed in open water and restore the fat layer they lost while incubating.


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