Giant pandas are able to survive on their meagre diet of bamboo partly by being frugal with the energy they spend on physical activity, scientists have found.
Researchers found that the metabolism of the panda is incredibly low - a 90kg panda expends less than half the energy of a 90kg human.
The panda, found mainly in China, is famous for being a meat eater turned vegetarian. In the wild its diet consists almost entirely of bamboo, but because its gut remains designed for digesting meat, this causes the bear huge problems.
Until now, how pandas survive on this poor diet has been a mystery, but it has been speculated that an essential component of their ability to do so is having a low energy demand.
The researchers measured the metabolic rates of pandas living both in captivity and in the wild.
"Pandas save a lot of energy by being frugal with the energy they spend on physical activity. Using GPS loggers attached to pandas we discovered that they rest for more than half of the day and on average, only travelled at 20 metres an hour," said Professor John Speakman, co-first author, from the University of Aberdeen and Chinese Academy of Sciences.
"However, it is not only their low activity that contributes to their low metabolism; the metabolic rate of an active panda is still lower than a completely stationary human.
"We found that their low metabolism is correlated with very low levels of their thyroid hormones, which was linked to a genetic mutation in the thyroid hormone synthesis pathway that is unique to the panda," Speakman said.
A big problem with having such a low metabolic rate is keeping warm, researchers said.
Pandas have exceptionally thick fur which traps what body heat they have inside, however this means that the surface temperature of pandas, which the team measured with a thermal camera, is much lower than other black and white animals, such as zebras and Dalmatian dogs.
The study is published in the journal Science.
