Today, giant pandas are represented by one iconic species, Ailuropoda melanoleuca, and they live only in the understory of particular mountains in southwestern China. They exclusively consume bamboo and have distinctive tooth, skull, and muscle characteristics adapted to a tough and fibrous bamboo diet. But according to new research by a team of scientists in China, ancient pandas had a more varied and complex diet. The study was published in the journal Current Biology.

“It’s impossible to know exactly what extinct animals ate,” said lead author Dr. Fuwen Wei of Chinese Academy of Sciences and colleagues.

“But we can get clues by analyzing the composition of stable isotopes in animal teeth, hair, and bones, including fossil remains.”

In the new study, Dr. Wei and co-authors first analyzed bone collagen of modern pandas and other mammals from the same mountains.

The stable isotopic composition of carbon and nitrogen from modern panda and other modern mammal bone samples indicated three obvious groups: carnivores, herbivores, and giant pandas.

The giant pandas were clearly unique, on account of their habit of eating bamboo.

Next, the researchers measured bone collagen isotopes of 12 ancient pandas collected from seven sites in southern and southwestern China and compared them to the patterns they observed in modern giant pandas.

The data comparison showed that ancient and modern pandas are isotopically distinct from one another, suggesting differences in their dietary habits.

There was also more variation among ancient panda species, suggesting that the niche they occupied was about three times wider than that of modern pandas.

That is, ancient pandas most likely had a varied diet, similar to that of other mammalian species that lived alongside them.

“Ancient pandas were probably not exclusive bamboo feeders,” the scientists said.

“Pandas’ dietary habits have evolved in two phases. First, the pandas went from being meat eaters or omnivores to becoming dedicated plant eaters. Only later did they specialize on bamboo.”

The study authors now plan to find when exactly pandas shifted to the specialized diet they have today.

They plan to collect and study more panda samples from different historical times over the last 5,000 years.

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Han Han et al. Diet Evolution and Habitat Contraction of Giant Pandas via Stable Isotope Analysis. Current Biology, published online January 31, 2019; doi: 10.1016/j.cub.2018.12.051