You’re eating what?
Pandas haven’t always had a bamboo-only menu. Tanya Loos reports.
Giant pandas are famed for eating only bamboo, and their skulls, teeth and even paws have morphological adaptations to help them gather and process the tough fibrous plants.
Now, new research suggests they may have adopted their specialised diet more recently than we thought.
"It has been widely accepted that giant pandas have exclusively fed on bamboo for the last two million years," says Fuwen Wei of the Chinese Academy of Sciences. “[But] our results showed the opposite."
Wei and colleagues used stable isotope analysis of bone and teeth fragments of both ancient and modern panda species to track dietary specialisation in pandas over time.
The findings, published in the journal Current Biology, reveal that giant pandas and their now extinct relatives were eating a wide range of plants well into the mid-Holocene, a mere 10,000 years ago.
It is difficult to assess the diets of long extinct animals, but stable isotope analysis reveals patterns that can provide clues. It involves examining different forms of the same element that contain equal numbers of protons but different numbers of neutrons.
The researchers compared the stable isotope composition of the bone collagen of modern pandas and a range of animals living in the same forests, and were able to pinpoint three obvious groups; carnivores, herbivores, and pandas.
Using these patterns as a base for comparison, they then measured the bone collagen isotopes of 12 ancient pandas from seven archaeological sites in southern and south-western China.
They discovered that the isotopic trophic niche width (the range of plant foods consumed) of ancient pandas was approximately three times wider than that of modern pandas. They speculate that “the ancient pandas might have had greater ecological flexibility than modern pandas have and that they may have lived in a more variable environment”.
Earlier studies place the transition of pandas from carnivore (like other bears) to bamboo specialists at approximately two million years ago, in the late Pleistocene. This study suggests that pandas had a broader herbivorous diet for some time in between these two phases.
The researchers say they would now like to figure out when exactly pandas shifted to the specialised diet they have today. To find out, they plan to collect and study more panda samples from different historical times over the last 5000 years.