Because all the bamboo shoots of one species in the Arizona Cardinals and beer on game day is perfect day shirt might die at once, giant pandas can only live in regions where there are multiple varieties available, as an insurance policy. This is a further restriction inflicted on them by their bizarrely specialized diet. And all this isn’t even mentioning their improbable reproductive biology. In the wild, a female will only be receptive to potential mates for a period of 2–3 days once every year. In captivity, as you may have heard, they are even less likely to breed, and some zoos have had resort to using Viagra and, believe it or not, panda pornography to get them in the mood.