Whiskers help animals sense wind direction: study

Have you ever wondered how your pet dog or cat senses which way the wind is blowing? Now, researchers have found this ability may lie, in part, in their whiskers.

"Nearly all mammals have whiskers organized in regular rows and columns on their cheeks. Scientists have shown that marine mammals, such as the harbor seal, can use their whiskers to track water currents," said Yan Yu, a PhD student studying at the Northwestern University and co-first author of the work, which appeared this week in the U.S. journal Science Advances.

"In land mammals, whiskers are well known to be involved in the sense of touch. But no one had ever looked at whether land mammals could also use their whiskers to sense air currents," he said.

Therefore, Yu and colleagues investigated the role of whiskers in a land mammal's ability to sense the direction of wind by placing five similarly aged female rats trained to locate wind sources from a particular fan on a circular table.

Along the table's circumference, five equally-spaced fans were positioned into a semicircle, and randomly turned on one at a time to blow air toward a same "start-door" located on the opposite side of the table.

A rat had to run from the door toward the fan blowing air, and go down a rat-sized hole directly in front of that fan. Each hole led to a tunnel beneath the table, where the rat was rewarded for choosing the correct fan.

After the rats had performed the task at a level of about 60 percent correct or higher for 10 days in a row, the researchers cut off the whiskers and looked for changes in behavior.

Ultimately, the team's results showed that whisker removal decreased rats' performance by approximately 20 percent on average.

The researchers said the performance drop indicated that rats use more than one cues to locate the fan but clearly they still rely heavily on their whiskers for this task.

To control the risk of the rats seeing or hearing the spinning fan, the experiments were performed in a dark room with added ambient noise.

To check for the possibility that rats were simply confused by the removal of their whiskers, another group of rats was trained to run to a light source instead of a wind source.

The team found no changes in the performance of these rats after whisker removal.

In an earlier experiment published in the Journal of Experimental Biology, the same group of researchers found that whiskers bend in the direction of the wind and that the harder the wind blows, the more the whiskers bend and vibrate.

"When the whisker bends, it presses on receptors at the whisker's base," co-first author Matthew Graff of the Northwestern University said in a statement. "Our behavioral work now suggests that this mechanical information is actually used by the rat to locate an airflow source."

While experiments have only been performed with rats, the team believed that whiskers of cats and dogs would also be used for flow sensing because they are arranged in a very similar way.

"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," such as finding food and potential mates as well as avoiding predators, Yu said.

"Now that we know that whiskers help animals localize airflow, we can work on artificial 'whiskers' that can be added to robots to track and follow plumes of odor and find explosives, chemical spills, and biological agents," he added. "Overall, this research could contribute to advances in robotic flow sensing and odor plume localization." Enditem