Yun, a 13-year-old giant panda on loan from China, gave birth
to the first of twin cubs, but researchers at the San Diego Zoo
were doubtful that the second cub would be born healthy with each
"The chances of her giving birth to a second live cub are
dwindling," said Pat Morris, the zoo's director of veterinary
services, at least 24 hours after the initial delivery.
Bai Yun gave birth in a nest of shredded bamboo at 1:15 p.m.
Tuesday, said Don Lindburg, head of the zoo's panda team. Bai
Yun appeared to have contractions into Wednesday but there were
no plans to intervene unless she showed signs of medical distress.
"The longer the birth interval, the less likely that the
second fetus will be born alive," Lindburg said. "We
are simply letting nature take its course."
Research has shown female pandas who are pregnant with twins
deliver the second cub anytime between 12 minutes and 12 hours
after giving birth to the first, according to the zoo's Web site.
Panda cubs can weigh from 4 to 6 ounces at birth.
Typically, a mother will chose to care for only one cub, officials
"It takes a lot of effort and a lot of intensity. That's
one of the obvious reasons why twinning is not successful in this
species," Morris said.
Bai Yun's newborn was about 4 inches long and covered with white
fuzz. It made squawking sounds about every half hour to indicate
it wanted to be fed - a positive sign, researchers said.
Normally pandas begin to develop their distinctive black spots
after two weeks, and open their eyes after two weeks to four weeks,
"We're really pleased that we have one," Lindburg said.
"It would have been a really nice treat for the community
if someday down the road they could have seen a couple of youngsters
playing here. I think it could probably still happen, but we really
aren't that hopeful that this will turn out that way now."
Bai Yun gave birth to a cub in 1999 after she was artificially
inseminated. Her offspring, Hua Mei, is the first U.S.-born panda
to survive into adolescence.
Giant pandas are an endangered species. Fewer than 1,000 exist
in the wild, all in China, and about 150 live in captivity, including
panda pairs at zoos in Washington, Atlanta, Tennessee, and Mexico