Why are giant pandas black and white?

Most people in the western world learn that the giant panda has striking black and white colouration at kindergarten; but are never told why! The question is problematic because there are virtually no other mammals with this sort of colouration pattern, making analogies difficult.

At UC Davis and CSU Long Beach, we instead decided to break up the external appearance of giant pandas into different regions roughly aligned with the species’ white back, rump, and face; and its black legs, shoulders, ears, and eye patches. This then enabled us to compare these body areas with those of other carnivores and bear subspecies (the giant panda is one of eight bears).

We scored each of these body areas on a light to darkness scale across 195 species of carnivores and 43 subspecies of bears, using about 2,500 photographs, and then asked what environmental variables are associated with light coloured backs and rumps? The answer is snow cover – white carnivores are found in areas where snow lies for much of the year – think of polar bears. Now we asked what variables are associated with dark legs and dark shoulders across species –deep shade. There was no association between temperature and the lightness or darkness of these areas.

Given that the giant panda occupies areas covered in snow for some of the year as well as dark subtropical rainforest at other times, it seems reasonable to argue that its external coloration has evolved to be cryptic in two different environments. Why does it have to make this compromise? The answer lies in its diet. Giant pandas eat 98% bamboo of extremely low quality. This prevents them from being able to put on enough fat to see them through a period of winter hibernation, so they will encounter snow. Think of a grizzly bear living in Canada. It puts on enough weight over the summer to allow it to sleep in a den throughout winter and thereby avoids moving in snow: it has a brown coat. The polar bear on the other hand does not hibernate and has white pelage.

In contrast to findings regarding the panda’s torso, we could find no associations between dark ears and dark eyes and living in shady habitats.

Instead, we discovered that pugnacious carnivore species often have black ears! Dark eye patches are found in species that are out in daylight (like the giant panda) suggesting they are used in communication. Interestingly the shape and size of the giant panda eye mask is highly variable (pear shaped or round) and laboratory work from Germany shows that giant pandas can remember the shape of these eye markings for up to a year. Thus dark eye markings may be involved in individual recognition. George Schaller, the great wildlife biologist who studied giant pandas in the wild, reported that losers in confrontations with other pandas covered their eyes with their forearms suggesting that these markings may be signals of dominance too.

So now parents can tell their children that giant pandas are black and white for at least three reasons! Nature just gets more and more interesting.

For more information, hover over the different areas of the panda below.

Featured image credit: Giant Pandas having a snack by Chi King. CC BY 2.0 via Wikimedia Commons.