The stork is on its way back to the San Diego Zoo's giant panda habitat. Zoo officials announced Thursday that the 13-year-old panda, Bai Yun, is pregnant again, with twins.
Keepers will begin a 24-hour birth watch Friday and say a birth could happen anytime over the next few weeks, said zoo spokeswoman Christina Simmons.
Researchers have been monitoring Bai Yun since April when she mated with male panda Gao Gao. Bai Yun has kept from public view since July 15 as she showed signs of a pregnancy, including nest building and loss of appetite. Two heartbeats were detected earlier this month during a routine check, but veterinary staff wanted to be sure before announcing a pregnancy. On Tuesday, they were able to observe both fetuses by ultrasound.
"The science is giving the pandas the environment they feel comfortable enough to breed. We've been lucky that we have an animal care staff that has developed a habitat and living situation that the pandas are very comfortable with," Simmons said.
Researchers warned that both fetuses might not survive. Veterinarians were unable to detect a heartbeat in one of the fetuses Thursday, Simmons said.
During Bai Yun's 2003 pregnancy two fetuses were detected but only one male cub, Mei Sheng, was born. It is believed the second fetus was resorbed in the womb, a process that may be common in giant pandas.
Bai Yun also gave birth in 1999 to a female cub, Hua Mei, the first surviving giant panda to have been born in the United States.
Hua Mei is now in China, where she gave birth last year to twins. Mei Sheng remains at the San Diego Zoo, but may also return to China when he turns 3 under the agreement that brought his parents to the United States.
Earlier this month, Mei Xiang, the giant panda at The National Zoo in Washington, D.C., gave birth to a cub conceived through artificial insemination.
Keepers at Atlanta's zoo said a panda there is also showing signs of pregnancy.
