Giant pandas love bamboo, and they love to sit around — and for a long time scientists have wondered just how this species sticks around and subsists on such a low-energy diet. But now they appear to have solved this vexing question.

A new study indicates that pandas, in fact, have found clever ways to conserve their energy, and their lazy lifestyle is key to that strategy, according to a Live Science report.

They also have small organs and special genes that allows them to survive on their favorite food: the fibrous and low-nutrient bamboo plant.

To make these findings, researchers followed five captive and three wild pandas with GPS trackers and by analyzing the chemicals in their fecal matter. They used this information to determine how much energy the pandas use in a day, and the results were surprising: pandas expend just 38 percent of the energy scientists would expect for an animal of its body mass. Scientists thought their metabolism would be low, but they were surprised to find it was this low — about the same as a three-toed sloth and less than that of the much smaller koala.

Only a handful of mammals have lower energy output than the panda: the Australian rock rat at 21 percent, and the golden mole at 26 percent of its expected energy.

The GPS recordings indicated that pandas are quite lazy and tend not to move around. And when they do move, they move slowly, as anyone who has witnessed them in the zoo can attest. They forage at a rate of just 50 feet per hour.

In addition, autopsies of pandas indicate they have smaller brains, livers, and kidneys compared to other bear species. This means they need less energy to function.