This week’s Santa Clarita Valley Outdoor Report by Wendy Langhans.
In order to get a driver’s license in the state of California, you must have a visual acuity (keenness of vision) of 20/40. By those standards, rats would not be able to drive, since they have a visual acuity of about 20/600. To a rat, the world looks “blurry”. So rats rely on their whiskers “to navigate effectively in their world”.
Whiskers, Why Animals Need Them
Whiskers have been around for about 120 million years and “with the exception of primates, nearly all mammals have whiskers.” Whiskers in mammals serve a useful purpose, sometimes as a supplement or sometimes as a substitute for short range vision. But not all whiskers are used in quite the same way. As an example, let’s compare cats and rats.
Cats “have about 24 moveable whiskers, twelve on either side of his nose, arranged in four rows”, as well as a few whiskers above their eyes and the outer edges of their cheeks. They use their whiskers like a a curb feeler on a car, to keep from bumping into objects. They also use their whiskers as a means of determining whether or not they will fit into a tight space. Cats move their whiskers by moving their cheek muscles.
Rats, on the other hand, have “a two-dimensional grid of five rows on each side of the snout, each row containing between five and nine whiskers ranging between ~15 and ~50mm in length.” Rats have muscles around each individual whisker, which allows them to engage in “whisking” behavior. Whisking is a quick, rhythmic movement, a vibration that occurs at about 3-25 whisks per second. It involves the “active brushing of whiskers against an object”, in order to determine the size and texture of an object. To see whisking in action, check out these videos from NPR.
Rats use whisking for a variety of purposes, including locating objects and identifying their shape and texture and movement. To this list I would add one more possibility: lima bean detection.
When our daughter Ellie was young, she had a pet rat, known as Stripe. Stripe had a reputation as a gourmet rat and he was especially fond of lima beans. Now, I can’t say for sure that Stripe relied only on his whisking ability to locate lima beans. Even with a blurry vision, rats can see ultraviolets, greens and blues. But I do know that when I held Stripe in one hand and placed a lima bean in the other, it didn’t take him long to find the bean and devour it.
Santa Clarita Valley Outdoor Report: By A Whisker
Upcoming Outdoor Events:
Trail Maintenance Schedule. Come join our volunteers as they help maintain our trails. Contact Steve at firstname.lastname@example.org for time and place.
Wednesday mornings, April 3, 10, 17, & 24.
Saturday mornings, April 6 & 20.
Blooms of the Season. April 27, 9:30 – 10:30 AM. Wildflower walk at Placerita Canyon.
New trail maps available. If you’d like to explore a bit on your own, the City of Santa Clarita has a website with trail maps of our local open spaces.
There’s also a new website for bicycle riders.
You can listen to stories like this every Friday morning at 7:10 a.m. on “The SCV Outdoor Report”, brought to you by your hometown radio station KHTS (AM1220) and by the Mountains Recreation and Conservation Authority.
Or check out our Facebook page – L.A. Mountains.
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