Their fur is black and white, but those are not the only colors giant pandas see.
A new study finds that two zoo pandas, Lun Lun and Yang Yang, were able to distinguish colors from shades of gray.
Although color vision is well studied in domesticated animals, such as cats and dogs, and also in primates, "color vision isn't too well studied in carnivores," said study leader Angela Kelling, a graduate researcher at Georgia Institute of Technology and Zoo Atlanta.
Kelling and her co-researchers decided to study color vision in pandas because the animals' cognitive and sensory abilities aren't yet well understood, and "we have such a rare opportunity having them at Zoo Atlanta," she said.
Most mammals are dichromatic — in other words, they can distinguish color from gray, although not colors from each other. Kelling says is most likely the case with giant pandas.
"They don't see [colors] the same way we do, but they are able to distinguish them as a separate color," Kelling said.
Dichromatism is usually attributed to the presence of only two cone cells in the retina of the eye. These cells are sensitive to higher-intensity light, with different types allowing for the detection of certain colors.
Humans and many other primates have three cones, and so are trichromatic. Marine mammals are usually monochromatic because their eyes operate in the low-intensity light that penetrates below the water's surface.
To test the pandas color-sensing abilities, Kelling presented the pandas with three PVC pipes, each hanging under a piece of paper.
Two of the pipes were hung under paper that was colored one of 18 shades of gray, with the third hung under paper colored one of five shades of three different colors — red, blue or green.
If the pandas pushed the pipe under the colored paper, they received a treat. Pushing the other pipes did nothing. The colors and shades of gray were mixed up through the trial.
Color vision was confirmed if the pandas pressed the colored pipe for 80 percent of the trials in three consecutive sessions.
Lun Lun, the female, passed for all three colors, while Yang Yang, the male, passed for two because a tooth problem prevented him from participating in the third trial.
"While this study shows that giant pandas have some color vision, it wasn't conclusive as to what level of color vision they have," Kelling said. "From this study, we can't tell if the pandas can tell the difference between colors themselves, like red from blue or blue from green. But we can see that they can determine if something is gray or colored."
The study was detailed recently in the journal Learning and Behavior.
Color vision could be useful to pandas in the wild by helping them distinguish healthy bamboo patches from brown and dying ones.
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