The newest sexual behaviour of a giant panda study has been published in a Biology of Reproduction magazine and is the first to shed the light over male giant pandas breeding abilities over time. It seems the female giant pandas are playing really hard to get, thus making the male pandas objective to spread their genes very difficult.
In order to mate, male giant pandas need to conquer great distances and rugged terrains, and when they arrive to their potential target, it is not self evident they will be "getting any". Mating season for a female giant panda starts in february and ends in may, that does not mean they are willing all the time during that period. Male panda has only one to three days to charm the lady and get her to accept him as a potentional father of her cubs. Considering all the facts, I would conclude, it's not easy being a male giant panda. :)