The seemingly identical food preference of red panda and giant panda is more than meets the eye, and it reveals valuable insight into how the species can co-exist.

Red pandas bare little resemblance and no genetic relation to giant pandas, yet they share the same food and geographic location, which has often been baffling to scientists.

Differences between the house-cat sized red panda, and the 225 pound giant panda are many, and new research into the red panda's feeding preferences reveals yet another: there are structural differences in the way the two animals chew, which is reflected in their distinct bamboo feeding preferences. Red pandas feed on the softest parts of the plant, while giant pandas munch on the tougher stems.

"Scientists have been studying the differences between red pandas and giant pandas for a long time because there's a basic principle in ecology that says if two species of an organism utilize the same resources, they cannot live in the same space. There's too much competition," said study author Z. Jack Tseng, a paleontologist at the American Museum of Natural History. "This research contributes to the body of work showing how the pandas co-exist. We've found that fundamentally, based on the structure of their skulls, they cannot eat the same things."

About 40 million years of evolution separates the red panda (Ailurus fulgens) from the giant panda (Ailuropoda melanoleuca). Red panda are the only member of their genus, but they are related to weasels. Giant pandas are members of the bear family and easily dwarf their red panda counterparts.

By creating a high-resolution, 3D model of the animal's skulls and teeth, the researchers were able to study the biomechanics of the animals' skulls, finding some distinct differences.

"These differences tie into the way that the species actually process bamboo," Tseng said in a statement. "The giant panda is a less-refined eater: it does a lot of chomping and swallowing. Their skulls are stronger overall, so the peak biting stresses are lower, meaning that they can eat harder and larger pieces of bamboo. The red panda has a weaker skull but it's better at distributing stresses, allowing it to chew longer and break down soft bamboo leaves more thoroughly before they swallow them."

The differences in eating behavior help explain how the two animals can share the same location and same food source but not be in competition.

Tseng and his collaborators published their study in the journal Biology Letters.