giant panda

Scientists in China have found that ancient pandas may have been carnivores or omnivores before eventually developing a specialized diet of bamboo.
Ancient pandas may have feasted on more than just bamboo, according to researchers in China. The findings are published in the journal Current Biology. Giant pandas live only in the understory of specific mountains in southwestern China, where they subsist on bamboo alone.

Their distinctive teeth, skull and muscle characteristics are adaptations to their tough and fibrous diet, while their special pseudo-thumb helps them better grasp and hold bamboo stems, leaves and shoots. However, scientists led by Professor Wei Fuwen at the Institute of Zoology of the Chinese Academy of Sciences have found that extinct and ancient panda species most likely had a more varied and complex diet.

"It has been widely accepted that giant pandas have exclusively fed on bamboo for the last two million years," said Wei. "But our results showed the opposite." While it is impossible to know exactly what extinct animals ate, researchers can get clues about ancient diets by analyzing the composition of stable isotopes-different forms of the same element that contain equal numbers of protons but different numbers of neutrons-in animal teeth, hair and bones, including fossil remains.

Wei's team thus analyzed bone collagen of modern pandas (1970s-2000s) 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. But when the scientists measured bone collagen isotopes of 12 ancient pandas collected from seven archaeological sites in southern and southwestern China and compared them to the patterns they observed in modern giant pandas, they observed that ancient and modern pandas are isotopically distinct from one another, suggesting differences in their dietary habits.

There was also more isotope variation among ancient panda species, indicating 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.

The researchers suggest that 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 researchers say they would now like to figure out when exactly pandas shifted to the specialized diet they have today. To find out, they plan to collect and study more panda samples from different historical times over the last 5,000 years.

The article can be found at: Han et al. (2019) Diet Evolution and Habitat Contraction of Giant Pandas via Stable Isotope Analysis.