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Though giant pandas may appear perfectly happy chewing bamboo, scientists recently discovered that just like the rest of us, they would rather have something a tad sweeter. This 'surprising' fact was disclosed to the world on March 26th, in the online scientific journal PLOS One by Danielle R. Reed, a behavioral geneticist at Philadelphia's Monell Chemical Senses Center.
The panda study was conducted as part of a long-term project to try understand how taste preferences and diet selection are guided by taste receptor genes. The researchers began with the hypothesis that carnivores gravitate towards meat, because over the years, their natural choice of diet has resulted in them losing their active sweet receptor gene. This means that they have no taste for sugars and hence, avoid them. Herbivores on the other hand, have a very active sweet 'tooth' which leads them towards the simple sugars that are present in plants, fruits and certain vegetables.
They selected the giant panda because the animals are largely herbivores, which theoretically would mean that their sweet receptor gene should be active. However, their choice of plant, the bamboo, has a very low sugar (about 1%) content and is therefore not considered sweet, at least by human standards. Could this mean that pandas had lost their penchant for sweet things?
In order to test this hypothesis, the team selected the eight lucky panda residents at China's Shaanxi Wild Animal Rescue Center. Through the course of the research, the pandas, that ranged from 3 to 22 years in age, were provided with two bowls to choose from - one containing plain water and the other, a sweet solution. Also, in order to eliminate the possibility that the animals were simply gravitating to the same bowl, the liquids were switched around, each time.
All in all, the pandas got to taste six kinds of sugars that are found naturally in fruits and vegetables. These include fructose, galactose, glucose, lactose, maltose, and sucrose. They were also given just five minutes to devour the liquids. In each of the taste tests, the animals picked the sweeter liquids and ignored the plain water completely. Though they seemed to enjoy all, it was the fructose and sucrose solution, the sugars present in fruits like peaches, watermelon, pineapples and apples, that the animals loved the most. According to the researchers, the pandas greedily gulped down over a liter of each, in the allotted five minutes.
What was even more interesting, is that when the water was mixed in with five different artificial sweeteners, ones that humans find palatable, the pandas were not as thrilled. In these tests they picked the plain water instead. The scientists believe that it could be either because pandas found them to be too sweet or not sweet enough. In order to ensure that the results were not biased by any factors other than taste, all the pandas got to try each of the treats twice!
The scientists were not too surprised by the results since pandas in captivity have always been partial to treats like apples, sweet potatoes and even mooncakes. Danielle believes that the bears may have once feasted on sweeter foods that were available in the lowland areas that they used to live in. But when human settlement pushed them to the bamboo forests in the mountains in Western China, they had no choice but to settle for the almost sugarless plants.
Fortunately, they have not evolved to the point of losing their sweet receptor gene. In addition to better understanding how the animals used to live before their habitats were disturbed by mankind, the research will provide a better understanding of what nutrients can be used to supplement the primarily bamboo diet that these endangered bears are currently fed. This hopefully means that the pandas that reside at places like the Shaanxi Wild Animal Rescue Center may now start getting yummy dessert on a regular basis!