Slow-Mo Video Shows Rats Using Whiskers to Follow Wind
New research helps explain why the rodents are so good at finding food and even predicting weather changes.
Photo: A close-up of a rat's face shows the arrangement of whiskers. Credit: Yan S. W. Yu, Matthew M. Graff, Chris S. Bresee, Yan B. Man, Mitra J. Z. Hartmann (2016)
With just a sniff and a twitch of their whiskers, rats can follow wind and other airflows, suggests new research that helps explain how the rodents can do everything from find food easily to predict weather changes.
The findings, published in the journal Science Advances, shed new light on some of the almost superpower-like abilities of rats.
For example, in 373 B.C., historians recorded that rats ran for their lives away from the Greek city of Helice, just before an earthquake leveled it. While the information that drove the rats to flee in that case remains a mystery, we at least know more now about how rat sensory abilities work. In terms of tracking wind flow, that phenomenon is known as anemotaxis.
"Our results indicate that rats can perform anemotaxis and that whiskers greatly facilitate this ability," lead author Yan Yu, of Northwestern University's Department of Mechanical Engineering, and colleagues wrote.
The researchers investigated rats' wind-whisker interaction by placing five similarly aged female rats, trained to locate airflow sources from a fan, on a circular table. Along the table's circumference, five computerized fans were positioned equidistant from one another and randomly turned on one at a time.
Rewarded at first with water and later a sugary solution, the rats searched for the source of the wind in a series of experiments conducted over a 10-day period. As this occurred, the scientists gathered data on the rats' navigation skills.
Here's what happened in slow motion:
(Videos created by Yan S. W. Yu, Matthew M. Graff, Chris S. Bresee, Yan B. Man, Mitra J. Z. Hartmann (2016) show how whiskers aid anemotaxis in rats.)
After this first set of trials, the scientists trimmed the rats' whiskers so that they were just tiny stubs and then repeated the experiments. While the rats still were able to track the airflow, they often moved in an awkward zig-zag way, becoming 20% less efficient at locating the blowing air.
Nevertheless, because the essentially whisker-less rats could still not be stumped by the researchers, other airflow-detecting mechanisms within rodents must be at work. The researchers believe that the rats sniff odor cues as they engage in "whisking."
Whisking is when the rat or other whiskered animal moves its facial whiskers (technically known as vibrissae) repetitively back and forth in a sweeping motion. They often do this while exploring an area or while on the go. The whisking happens at anywhere from 3 to 25 whisks per second.
While all of this whisking is taking place, the rat or other whiskered animal is also sniffing the air, suggesting that the behaviors are synchronized by shared regions of the individual's nervous system.
It should be mentioned that human-grown beards are sometimes referred to as whiskers, but these hairs lack the specialized structure of vibrissae that in rodents, cats, dogs and many other animals sends information directly to the brain.
As Nick Crompton, a University of Cambridge zoologist, told The Naked Scientists: "Beardy chaps don't have this sort of specialization within our brains and, in fact, humans are almost unique in being one of only two mammals known not to sport any vibrissae at all, along with the anteater."
"But it's recently been reported that the muscles used to move whiskers around are present in the human lip, but as very degenerate vestigial structures," Crompton continued. "Now our beards are more than likely the result of sexual selection, like the mutton chops and mustaches on some old-world monkeys, and they just help their owners look dashing, if maybe a little bit scruffy."