SAN DIEGO ZOO

Giant Panda

A day and a half after a giant female panda gave birth to the first of twin cubs, the second cub still had not been born and researchers said it was unlikely another delivery would be successful.

Bai Yun, a 13-year-old female on loan to the zoo from China, was doing well after delivering the first cub Tuesday afternoon, and was nursing it and cradling it close to her body, experts said.

She appeared to have contractions again late Wednesday night, but their significance wasn't clear, zoo spokeswoman Yadira Galindo said Thursday. Most successful twin panda births occur within 12 hours of each other, though other bear species have given birth to twins as much as 30 hours apart, Galindo said.

Don Lindburg, head of the zoo's panda team, said there were no plans to intervene unless the panda showed signs of medical distress.

Bai Yun was being kept in a private pen, beyond the view of zoo visitors. Her 4-inch-long cub was making squawking sounds about every half hour to be fed, which experts said was a positive sign.

The cub's birth was the first in the United States since 1999, when Bai Yun delivered a female panda, Hua Mei, the first U.S.-born panda to survive beyond adolescence.

Only about 1,000 of the endangered giant pandas are thought to live in the wild, all in China.

The baby panda will be in exhibit sometime in January of the year 2004