Births of pandas in captivity hit record number
(Washington Post)
Updated: 2005-11-25 14:57

Three of this year's births in China took place at Zhang's institute, which houses 48 pandas in a series of compounds strewn with bamboo stalks and built to resemble the hillsides where pandas live naturally. Sixteen other births, including two instances of twins, occurred at the Wolong Giant Panda Breeding and Research Center, a sister institute 80 miles northwest of Chengdu and nearer to the panda's natural habitat.

The biggest reason for this year's record and the hope of more high numbers in the future, Zhang said, is that a growing number of captive pandas are reaching mating age, 5 years old for females and 6 or 7 for males.

The broader the circle of possible suitors for each female, the higher the chances that she will accept a male for natural fecundation, said Zhang, a veterinarian and geneticist by training. And if artificial insemination is still necessary, as is likely, he added, the wider selection of males will mean a wider gene pool and stronger animals with a higher survival rate.

The goal, Zhang added, is to reach a point where the captive pandas reproduce naturally and become numerous and strong enough that they can be released into the wild. "But we still have a long way to go," he said, "because if we want to have a self-sustaining panda population, we need a bigger pool of individuals, because we need a relatively high genetic diversity."

A key step came in 1980, when scientists learned how to preserve the male's sperm by freezing it in liquid hydrogen. Since then, he said, they have little by little learned how to understand when the female is ready to conceive, a period of only a few days each year. The prospective mother emits a distinctive sound when she is ready, he added, and her sexual organs change color, turning red then white.

If conception occurs, baby pandas remain in gestation for 160 days, after which one or two cubs are born.