Why are giant pandas born so tiny?
Anewborn panda cub typically weighs about 100g, which is getting on for a thousandth the size of its mother. Among mammals, only kangaroos and other marsupials are born smaller, relative to their parents, but they have the luxury of continuing their development safe in their mother’s pouch. It’s something of a mystery why pandas are born so minuscule. One theory is that it may be connected with their low-energy bamboo diet. Another is that it’s the result of bears’ tendency to hibernate, because if pregnancy overlaps with hibernation – during which a female does not feed – producing a larger cub might be too big a drain on her resources. Indeed, other bear species also produce relatively small offspring, albeit none as tiny as in pandas. Unfortunately for this theory, giant pandas don’t themselves hibernate, though it remains possible that small babies are a legacy inherited from a hibernating ancestor.