Despite the popular conception of giant pandas as continually chomping（格格地咬牙） on bamboo to fulfill a voracious（贪吃的） appetite for this reedy（芦苇丛生的） grass, new research from the Monell Center reveals that this highly endangered species also has a sweet tooth. A combination of behavioral and molecular genetic studies demonstrated that the giant panda both possesses functional sweet taste receptors and also shows a strong preference for some natural sweeteners, including fructose（果糖） and sucrose（蔗糖）. "Examining an animal's taste DNA can give us clues to their past diet, knowledge that is particularly important for endangered animals in captivity," said study author Danielle Reed, PhD, a behavioral geneticist at Monell. "This process can provide information on approaches to keep such animals healthy."

The Monell researchers studied the giant pandas as part of a long-term project focused on understanding how taste preferences and diet selection are shaped by taste receptor genes.

One previous study found that cats, which must eat meat in order to survive, had lost the ability to taste sweets due to a genetic defect that deactivates the sweet taste receptor.

Although giant pandas and cats belong to the same taxonomic order, Carnivora, the giant pandas have a very different diet, as they feed almost exclusively on bamboo.

Noting that bamboo is a grass-like plant that contains very small amounts of sugars and does not taste sweet to humans, the researchers wondered whether giant pandas, like their Carnivora cat relatives, had lost sweet taste perception. An alternate possibility was that the panda maintain a functional sweet taste receptor, similar to other plant-eating mammals.

In this study, published online in the open-access journal PLOS ONE, eight giant pandas between three and 22 years of age were studied at the Shaanxi Wild Animal Rescue and Research Center in China over a six-month period.

For taste preference tests, the animals were given two bowls of liquid and allowed to drink for five minutes. One bowl contained water and the other contained a solution of water mixed with one of six different natural sugars: fructose, galactose, glucose, lactose（乳糖）, maltose（麦芽糖）, and sucrose. Each sugar was presented at a low and a high concentration.

The pandas preferred all the sugar solutions to plain water. This was especially evident for fructose and sucrose, as the animals avidly consumed a full liter of these sugary solutions within the respective five-minute test periods.

"Pandas love sugar," said Reed. "Our results can explain why Bao Bao, the six-month-old giant panda cub at the National Zoo in Washington, DC, is apparently relishing sweet potato as a first food during weaning（断奶）."