Pandas reproduce through mating in a procedure that is similar to other mammals; the mating season occurs between March and May, when the female has a two- or three-day period of estrus. At that time, the male mounts the female panda, copulating for a period of time between 30 seconds and five minutes. Gestation then lasts between 95 and 160 days.
If the mother gives birth to twins, generally only one survives in the wild. The mother selects the stronger cub and leaves the weaker one to die. Because mothers store no fat, they do not have the ability to produce sufficient milk for two cubs, and the father does not participate in raising the cub.
While pandas are black and white as adults, cubs are born pink, unable to see and having no teeth. Their average birth weight ranges between 3 and 4 ounces. Over the next two weeks, the cub's skin turns gray at those points on the body where it grows black fur. Giant panda cubs stay with their mothers for the first 18 to 24 months of life.
Pandas in captivity have a difficult time completing the mating process, as the environment seems to remove their desire to mate. Some researchers have attempted to give males Viagra and show them movies of pandas mating to increase their motivation.