Panda Couple a Model of Fertility

Suggesting that quality does best quantity, two of the most reproductively successful pandas in captivity meet—and mate—but once a year, the AP reveals. Since 2003 the San Diego Zoo's Bai Yun and Gao Gao have produced three cubs, a great feat for the endangered species. The youngest is to be named today, when she reaches 100 days old, following Chinese tradition.

Fertile just 3 days a year, the naturally solitary Bai Yun is penned separately from Gao Gao. "For 363 days a year they don't want to have anything to do with each other," says a keeper. When she's in heat, he mates for a day then loses interest again. "Day two or day three, when she's still exhibiting interest, he just has nothing to do with her," says another keeper. "He seems to be a one-shot guy, but she's gotten pregnant each time.”  (More panda stories.)