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Research Progress

Cool Pandas

Jul 14, 2015

Research by scientists from the Chinese Academy of Sciences (CAS), the Beijing Zoo and the University of Aberdeen shows that pandas are cool. No, not slang “cool” – although that may be true, too – but colder in temperature than creatures of similar coloration.

The research, led by Professor WEI Fuwen of the CAS Institute of Zoology in Beijing and published today in Science, measured the metabolism of both captive and free-living pandas and revealed some amazing data. 

The giant panda, which is native only to China, has long captured people’s attention due to its unusual appearance, lumbering gait and gentle passivity. This research shines a light on some of those characteristics. 

If pandas move slowly, one reason is their slow metabolism. The critically endangered animals’ low metabolism allows them to survive on a vegetarian diet of bamboo, despite originally being meat eaters. Their low energy expenditure is linked to low levels of physical activity and low levels of thyroid hormones probably caused by a genetic mutation in the thyroid hormone production pathway. 

Pandas in the wild, of which there are only about 2,000 left, eat a diet consisting almost entirely of bamboo. However, while the giant panda is no longer carnivorous, its gut remains essentially designed for digesting meat. Since bamboo is not easy to digest, pandas must eat up to 50 lbs. of bamboo a day to survive! 

Scientists have long suspected that pandas must have low metabolic rates in order to achieve an energy balance. Up until now, however, no one has managed to measure pandas’ metabolism. The current research, which measured the metabolism of pandas both in the wild and in captivity, shows that panda metabolism is incredibly low – about the same as a sloth. In comparison with humans, pandas use far less energy. For example, a 90kg panda expends less than half the energy of a human of the same weight. 

How do pandas achieve such low metabolic rates? There are several contributing factors. First, pandas are very frugal in the energy they expend on physical activity. By using GPS loggers attached to free-ranging wild pandas, the study in Science showed that pandas rested for more than half the day and on average travelled just 20 meters (less than 22 yards) per hour! 

But low activity is only half the story. The metabolic rate of an “active” panda is even lower than a completely stationary human. The secret to the low metabolism of the panda, the study in Science shows, is that the animals have very low levels of thyroid hormones, which is probably linked to a unique mutation in a gene that is critical for thyroid hormone synthesis. This may be instrumental in lowering not only their activity, but also their resting metabolism. 

One problem with having such a low metabolic rate is maintaining body heat. The answer lies in the panda’s exceptionally thick fur, which traps its meager body heat inside. This means the surface temperature of pandas, measured using a thermal camera, is much lower than other black and white animals like zebras and Dalmatian dogs. In other words pandas are literally COOL! 

The study was funded by the National Natural Science Foundation of China and the Chinese Academy of Sciences.  

Reference: NIE et al. (2015) Exceptionally low daily energy expenditure in the bamboo eating giant panda. 

 

Thermal image of giant panda (Image by NIE Yonggang) 

 

Wild panda in the Foping Nature Reserve eating bamboo (Image by WEI Fuwen) 

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