Why are China's giant pandas so lazy?
They eat and lie around. Then they eat some more, and maybe lie around some more.聽
But giant pandas aren't just lazy 鈥撀爐heir low-key lifestyle serves a purpose.
A study on Friday reveals that giant pandas get very little energy from their diet, so their metabolic rates are low.
After monitoring the hourly behavior of three wild and five captive pandas, the China-based research team found that pandas use only a third to a half as much energy as other large mammals. The captive pandas鈥� daily energy expenditure was 38 percent of what would be expected for large mammals, while wild pandas used 45 percent.
The problem is their diet: bamboo. Like celery, bamboo is low in calories and high in fiber, with the result that pandas have little energy to burn.
To meet their energy needs, pandas must eat聽 of bamboo every day 鈥� and that still gives them barely enough energy to move to the next clump of bamboo.
"Giant pandas have exceptionally low [daily energy expenditure], which may facilitate survival on their diet of bamboo,"聽.
That explains pandas' lazy lifestyle.
In addition, pandas have a smaller brain, liver, and kidney than other mammals their size, as well as under-active聽thyroid glands.聽, "its thyroid hormone levels are only a fraction of the mammalian norm 鈥� comparable to a hibernating black bear鈥檚 hormone levels."
The pandas' low metabolic rate does not mean that they are always cold; their thick coat of fur helps them聽.
Ancestors of today鈥檚 pandas ate both meat and plants, but they gradually switched to their almost bamboo-exclusive diet between 7 million and 2 million years ago.
While modern pandas鈥� daily diet consists almost entirely of various bamboo species, about one percent of their diet includes other plants , such as pikas and small rodents, according to the聽World Wildlife Fund (WWF).
Pandas love bamboos even though they can not digest it very efficiently. A study published in May found that pandas聽digest about 17 percent聽of the bamboos they eat throughout the day.
According to WWF's latest census, in 2014 there were , an increase from around 1,000 in the late 1970s. In the past decade, giant panda numbers have risen by 17 percent, but they are still considered an endangered species,聽聽habitat loss and fragmentation, as well as hunting.
The giant panda鈥檚 habitat once stretched throughout southern and eastern China, as well as Myanmar and northern Vietnam, but they now live only in zoos and聽, WWF reports.
