Why are panda bears vegetarian?

Panda bears have six toes on each of their front feet. Actually, five and a fake thumb. This “sixth finger” is vitally important to them: it allows them to grasp the bamboo stalks that make up the bulk of their diet. And so much: a panda spends up to 15 hours a day eating and in that time can eat about 45 kilos of bamboo. But why is the panda a vegetarian? Was it always or did it go from meat to bamboo? When was that and why?

These questions paleontologists asked themselves. A group of researchers from Natural History Museum of Los Angeles County (United States) and the Chinese Academy of Scienceshave responded to most of them and thus have solved the mystery of why panda bears are vegetarians.

Panda bear

According to his study, published in the Scientific Reports (of Nature), panda bears have been eating bamboo for at least six million years. The scientists, led by paleontologist Xiaoming Wang, have been based on the oldest fossil evidence of that sixth finger (that false thumb) that pandas and their ancestors use to hold bamboo.

His work recalls that the giant panda’s false thumb “it has become a famous case of evolutionary adaptation”. According to the researchers, the panda “It’s a striking example of a highly specialized member of the bear family becoming a dedicated herbivore, a rare case of a large carnivore with a short digestive tract becoming a low-level consumer with a gut microbiota. very upset».

Modern panda bears (Ailuropoda melanoleuca) have an enlarged wrist bone (called the radial sesamoid) with a thumb-like structure that they use to manipulate bamboo. That pandas have that “sixth toe” has been known to science for a century, but the new study explains how and why.

The fossil of a bear from millions of years ago

Wang’s team has examined this bone in fossils belonging to a (now extinct) ancestor of the panda called ailurctosthat lived in China between six and eight million years ago, and that they were discovered in Shuitangba, near the city of Zhaotong, in the Chinese province of Yunnan.

They compared it to the wrist bones of modern pandas and arctoid indarctoid, an ancient bear that lived nine million years ago and may share the same common ancestor as pandas. They found that the thumb-like structure of the modern panda has the same distinctive shape as the bone of the doll of ailurctosbut not the one of I. arctoideswhich was larger, wider and more hooked.

So the false thumb was not in the common ancestor which it shares with pandas, but has been present within the lineage of these animals and has been used to grab bamboo for at least six million years.

The Sino-American team of researchers understands that the hook turned out to be valid so that the modern panda could better grasp the bamboo, while the shorter length and flattened outer surface helped with weight distribution when walking. However, not being able to support much weight, that “thumb” would not have evolved into a full finger.

Thus, the panda bears swapped their omnivorous diet for bamboo, that is, they went from a diet rich in protein to another poor in nutrients. But in the south of China there is always bamboo. That is also why they spend so many hours of the day eating.

Font: 20 minutes

Reference article: https://www.20minutos.es/noticia/5025074/0/por-que-los-pandas-son-vegetarianos-un-estudio-lo-explica-a-traves-del-desarrollo-de-un-sexto- finger/