Science: Penelope’s Secret

For six years the earnest curators of New York’s Bronx Zoo have busied themselves with the delicate problem of platypus family life. Platypus reproduction is a baffling business, for platypuses are not quite mammals. Their blood is warm and they have mammal-like fur, but they lay soft, reptile-type eggs about ¾ in. long. From the eggs hatch blind, hairless little “larvae” that nurse by licking milk from their mother’s mammary pores. Only after several months do they frisk out of their burrow as furry platykittens.

Even in their native Australia, only one platypus couple (Jack and Jill) have bred in captivity, and they produced only one offspring. But the Bronx curators were not discouraged. When they got three live platypuses in 1947 (TIME, June 9, 1947), they devised elaborate plans for breeding the two females. One of the three, Betty, died of a cold. But Penelope and Cecil, the male, seemed to adjust themselves gradually to the alien Bronx. Penelope and Cecil were fed extravagantly on worms, insect larvae, frogs and water plants. In summer each had an outdoor private swimming pool, and in winter they retired to an indoor platypusary.

Evasive Tactics. They both seemed happy in a proto-mammalian way, but the curators were ambitious for them. On a warm spring day in 1951, they placed Cecil in Penelope’s half of the platypusary. As soon as she saw him, she took evasive tactics, dashing into the water, rolling over and over and scratching furiously with all of her 20 sharp claws. Cecil seemed interested, but decided that he was not welcome. He made no overtures.

The same routine was repeated in the spring of 1952. But last June. Penelope seemed to be in a more sociable mood. When she scratched timidly at the wooden barrier that separated her from Cecil, the curators happily lifted Cecil over the barrier. Nothing overt was observed, but Penelope was no longer evasive and the two platypuses seemed to get along nicely. When the curators provided her with eucalyptus leaves. Penelope took them into the burrow. Since wild platypuses make their breeding nests out of just such leaves, the curators grew hopeful.

On July 9 Penelope retired to her burrow and did not appear again for six days. She ate an enormous meal and popped back again. The curators hovered around, smiling at one another like fond godfathers. All the signs pointed to platypus eggs, perhaps even hairless platypus infants wriggling in the nest.

Eating for Two. Then came long and anxious waiting while the presumed young platypuses passed through the nursing stage. Penelope kept her own council, but she seemed to be eating for two or more. Huge quantities of worms and larvae disappeared into her duck bill. Her offspring were presumably demanding more and more milk. According to the schedule worked out in Australia, they should come into the outside world after 17 weeks.

Sixteen weeks passed. The weather in The Bronx grew cold; the fondly expectant curators grew worried. At last they decided that they should wait no longer. Last week, working carefully with small trowels under the eyes of 50 newspaper reporters and photographers, they dug into the dirt to bare Penelope’s secret. They found a network of burrows; they found Penelope. But they found no leafy nest —and no platykittens.

Penelope had apparently had a false proto-pregnancy.