We humans have all kinds of ways to determine which way the wind is blowing. We could consult a weathervane, or hold out a freshly-licked finger, or watch which way the inconsiderate gusts fling our freshly-brushed hair. To the best of our knowledge, other mammals don’t use any of these techniques. Exactly how they do it has been something of a mystery—until now. Researchers say that rats (and most likely other mammals as well) sense air and wind direction through their whiskers. They published their findings in the journal Science Advances.

The act of following the wind is called anemotaxis, after the Greek Anemoi, or wind gods. Most of what we know about anemotaxis pertains to flying insects, which have elevated wind-surfing into an art form. And while land mammals may not be riding the currents, they do rely on air currents to evade predators, find mates, and locate food.

To figure out how the animals do it, researchers at Northwestern University designed a circular arena for lab rats. On one side of the circle were five fans, and in front of each fan was the entrance to a small tunnel. At the end of the tunnel was a reward. The scientists turned on the fans at random, one per round, and trained the rats to run to the tunnel directly in front of whichever fan was blowing. At first, the rats were allowed to use all of their senses to sort out the source of the wind, from the ruffling of their fur in the breeze to the sound of the fan itself.

After 10 consecutive days of testing, the rats were able to pass the test approximately 60 percent of the time. The researchers then trimmed the rats’ whiskers, leaving all their other senses intact. With no whiskers, the rats’ success rate dropped by 20 percent.

The researchers say that the fact that they were still able to find the fan sometimes suggests that they rely on multiple forms of sensory input. "The rat clearly uses more than one cue," co-author and neuroscientist Chris Bresee said in a statement. "But rats still choose to rely heavily on their whiskers, which suggests that whiskers facilitate wind-sensing even when wild rats explore naturally."

Previous studies from the same research team have shown that rats’ whiskers bend in the same direction as the wind. The harder the wind blows, the more they bend.

Although this study included only rats, the researchers note that the whiskers of cats, dogs, and other mammals are arranged quite similarly. "It would make sense for all sorts of animals to exploit this mechanical information, given that sensing wind direction is important for so many behaviors," said co-first author Yan Yu.

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