Appendix: What makes the giant panda non-territorial?

There are probably at least two reasons. First, there is really no need to be territorial as the most important resource, food - in this case, bamboo - is abundant and so does not need to be defended. Second, bamboo is so nutrition-ally poor that finding and eating sufficient to sustain life is arduous enough without adding another energy-expensive activity such as territorial patrol. Because they do not have this extra energy burden, giant panda males can afford to have home ranges big enough to encompass several female ranges. The only alternative would be to defend a small territory, but this would not only mean fewer potential mates, it might mean none at all if a higher status male were to oust him. Having a virtually communal home range rather than a freehold territory means that neighbouring males may also share the same resident females and so the males compete with each other for females. The males that come off best are those of high rank. Rank is based on size, age and experience, and is established through olfactory communication long before the start of the breeding season.