On Sunday, July 29 at a little after 11 am PST the giant panda team at the San Diego Zoo observed signs of labor in Bai Yun, a 20-year-old female giant panda at the San Diego Zoo.
Researchers estimate that she delivered a cub at 2:10 pm while watching the Zoo’s closed-circuit camera that is mounted inside the birthing den. This birth makes Bai Yun one of the oldest giant pandas known to give birth to a cub. This is also the sixth cub born at the San Diego Zoo, the most born at a breeding facility outside of China. All six giant panda cubs have been born to Bai Yun.
Newborn giant panda cubs are born pink and grey, without sight and weigh an average of 4 ounces, or 112 grams. Their trademark black-and-white markings develop within the first months. The sex of the cub will not be known until animal care staff examine the cub, which is expected to happen in approximately two months.
Scientists and veterinarians at the San Diego Zoo have been observing denning behavior from Bai Yun since June. Impending birth of a giant panda is predicted on the basis of behavioral, hormonal and anatomical changes. Ultrasounds and thermal imaging has been used to track the development of the fetus, and Bai Yun’s hormone levels have been measured through fecal and urine samples. .
The last cub born at the San Diego Zoo was on Aug. 5, 2009. It was a male named Yun Zi, which means "son of cloud."