Panda's Life Cycle
Scientists once believed that the giant panda bear was a species of raccoon, but genetic testing in 1995 confirmed that pandas are true bears, although they have an unusual adaptation not seen in any other species of bear, a sixth digit on their front paws that help them grasp food. Another uncommon feature is that giant pandas share territory peacefully, even during mating season.
Giant pandas reach sexual maturity when they are around five years old and remain reproductive for the next 15 years. The female giant panda is in estrus for one to three weeks every spring but receptive for only a few days during that time. Mating calls and scent markers help the males and females locate each other.
Gestation time for the female giant panda is from 95 to 160 days. She can hold off whelping until environmental conditions are optimal for survival. Litter size is generally one to three cubs, although in the wild it's unusual for more than one to survive. The female will usually choose the strongest cub in the litter and allow the others to die.
The newborn cubs weigh between three and five ounces and are around six inches long, hairless and totally dependent on the mother. Their eyes do not open until they are six to eight weeks old, and they are not mobile until they are three months old. The cubs nurse until they are nine months old, but do not strike out on their own until they are at least two years old.
The young adults will wander their territory for the next two to three years until they are sexually mature and ready to mate. They use this time to search out the best feeding and resting areas. The females will usually stay within the same territory as their mother, while the males will typically wander further afield. It's not unusual for small groups of these young adults to feed and play together when they meet.
Because a female will not mate while she is caring for a cub, she typically mates only every two to three years. Adult males are tolerant of the young and have never been observed killing a cub to force the female to come into estrus as some bear species, such as the polar bear, have been known to do. Scientists have not been able to accurately estimate how long the wild panda lives, but captive pandas have lived for as long as 38 years, with the average lifespan being twenty years.