March 27, 2014
Despite A Big Bamboo Diet, Giant Pandas Love The Taste Of Sugar
Lawrence LeBlond for redOrbit.com - Your Universe Online
It’s no mystery that giant pandas have a voracious appetite for bamboo, but new research from the Monell Center also shows that these endangered mammals of the Ursidae family also have a taste for sugar.
A combination of behavioral and genetic studies have revealed that giant pandas possess functional sweet taste receptors. Due to this receptor, it has been shown that the pandas have a strong preference for natural sweeteners, such as fructose and sucrose.
"Examining an animal's taste DNA can give us clues to their past diet, knowledge that is particularly important for endangered animals in captivity," study author Danielle Reed, PhD, a behavioral geneticist at Monell, said in a statement. "This process can provide information on approaches to keep such animals healthy."
The panda study is part of a larger long-term project to better understand how taste preferences and diet selection are shaped by taste receptor genes. Oddly enough, pandas subsist largely on a diet of bamboo, despite belonging to the order Carnivora. A previous study had found that cats, which also belong to the order Carnivora and must eat meat to survive, lost the ability to taste sweets due to a genetic defect that deactivates the sweet taste receptor.
Researchers were interested in knowing if pandas had also lost the ability to taste sweet as the sugar in bamboo is so minute that it cannot be picked up by human taste. The Monell team suggested that it was also possible that the panda retained its functional sweet taste receptor, keeping in line with other plant-eating mammals.
In Reed’s study, published in the open-access journal PLOS ONE, eight giant pandas between the ages of three and 22 were studied at the Shaanxi Wild Animal Rescue and Research Center in China over a six-month period.
Similar to popular human-based taste tests, notably those involving Pepsi and Coca-Cola, the study team had given the pandas two bowls of liquid and allowed them to drink for five minutes. One bowl contained water and the other contained a solution of water with one of six different natural sweeteners: fructose, galactose, glucose, lactose, maltose and sucrose. The team offered the sweetened water in both high and low concentrations to each panda over the six-month period.
It was plainly evident that the pandas preferred all the sugar solutions to just plain water, with those containing fructose and sucrose being the most popular choices, as the bears all consumed a full liter of the sugary solutions easily within the five-minute test sessions.
"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."
In a separate experiment as part of the same study, Reed and colleagues offered the pandas a series of artificially-sweetened water bowls. In all five artificial sweeteners used, the pandas showed little to no preference for any of them, suggesting that pandas either cannot taste or do not like the compounds in artificial sugars.
In confirming that the pandas did in fact use their sweet taste receptors to taste sugars, the team conducted parallel cell-based studies by using panda DNA. They isolated the sweet taste receptor genes and inserted them into human host cells grown in the lab. The cells responded vigorously to sugars but not to most artificial sweeteners.
"This is the first study to address taste perception in the giant panda as it relates to feeding behavior. We hope to extend this research further to examine bitter taste perception," said lead author Peihua Jiang, PhD, a molecular biologist at Monell. "The results could have significant implications for the conservation of this endangered species as their naturals habitats continue to be demolished."