As Cole Porter once quipped, birds do it, bees do it, even educated fleas do it. Pandas do it too, when they're in the wild. Put them in captivity though and things get a lot trickier.
That's worrisome considering there are only about 2,000 pandas alive today and a sixth of them are in captivity. David Owen recently wrote about the challenges of getting pandas to reproduce for the New Yorker magazine.