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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.
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