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The best way to tell if a rat’s happy, according to a new study, is to look at its ears. A happy rat’s ears hang relaxed to the sides (right), instead of perked up (left).
Do rats feel joy? It can be hard to tell, since they can’t exactly greet us with a grin.
But now, for the first time, scientists have spotted the rat equivalent of a smile—and it’s all in the ears.
They found that happy laboratory rats not only can be literally tickled pink, but they relax their ears so that they hang loosely to the side.
The study is the first to look for signs of positive emotions on rats’ faces, such as pleasure or happiness. Other research on rat facial expressions has focused mainly on pain, showing that suffering rats narrow their eyes or squeeze them shut, flatten their nose and cheeks, and curl their ears forward. There’s even a rat "grimace scale" to measure pain levels.
Recognizing when an animal is happy or in pain could help people give captive animals a better quality of life, says Luca Melotti, an animal-behavior expert at the University of Bern in Switzerland and an author of the recent study, published in the journal PLOS ONE.
Read more here. (National Geographic)
