Washington, July 12 (IANS): Throwing fresh insight into the secretive life of pandas, a new study finds that giant pandas have clever ways to conserve energy, including having lazy lifestyles, small organs and special genes.

Giant pandas have an insatiable craving for bamboo, but scientists have long wondered how the bears survive on such a fibrous and low-nutrient plant.

The researchers followed five captive and three wild giant pandas (Ailuropoda melanoleuca) for about a year.

By using GPS trackers and analyzing chemicals excreted in the pandas' poop, they were able to measure the amount of energy the pandas spent each day.

Surprisingly, the pandas expended only about 38 percent of the energy that an animal with the same body mass would require.

"We thought the metabolism of the panda would be low because the bamboo diet contains low energy," said senior author Fuwen Wei, a professor of zoology at Chinese Academy of Sciences, Beijing.

"But it is very surprising that it is this exceptionally low, equal to the three-toed sloth, and much lower than the koala," Wei pointed in the journal Science.

The researchers found several ways how pandas save calories.

The GPS recordings showed that pandas are a lazy bunch. When they move, they move slowly.

The wild pandas forage at an average speed of 15.5 metres an hour, which is "very low".

By studying giant panda's autopsy data, the team found that relative to their size, the animals have a smaller brain, liver and kidneys than other bears.

These small organs most likely need less energy to function, saving the pandas precious calories.

Compared to other mammals, the pandas have smaller thyroid hormones. Their two key hormones are about half of what is seen in mammals with the same body mass.

The panda's lazy lifestyle, small organs and thyroid hormones likely help it conserve energy, allowing it to continue munching on its favourite low-nutrient snack: bamboo.