Why do cats and dogs have whiskers

Most cats and dogs have hair but their whiskers are longer, thicker and more rigid, as well as more deeply embedded in the skin. Each whisker is rooted in a hair follicle that's filled with blood vessels and nerves. And like other hairs, whiskers will occasionally fall out and grow back. 

Most cats have 12 whiskers that are arranged in four rows on either cheek, but the whisker pattern in dogs is more varied. Whiskers can also sprout above the eyes, as well as under the chin. Cats can also grow whiskers behind their wrists. 

The primary function of whiskers is to aid with vision, especially in the dark, by providing additional sensory information - much like antennae on other creatures. 

Although it's often called "tactile hair," the whisker itself cannot feel anything. Instead, objects that brush up against a whisker cause it to vibrate, which then stimulates the nerves in the hair follicle. This explains why the scientific name for whiskers is vibrissae, which derives from the Latin word, vibrio, meaning "to vibrate."

Cats use their facial whiskers to determine if they can fit into narrow spaces, and the whiskers on their legs may aid them in sensing prey or climbing trees. 

Whiskers serve a similar purpose in dogs: Nearly 40 percent of the canine brain can detect when something touches a dog's face, especially the region where the whiskers are located. 

Dogs and cats can also sense something even if it doesn't actually touch a whisker. For example, a pet in a dark room can pick up on the fact that there's a wall nearby because of a change in air currents. 

Some whiskers, especially those above the eyes, can also protect a pet from getting poked by long grasses and other objects. 

The position of the whiskers can also clue you in to the mood of an animal. For example, felines may fold their whiskers back to say, "Stay away." 

Although it's an old wives' tale that cutting a pet's whiskers off will affect his balance, it can compromise his ability to "feel" around his face. In other words, if you're tempted to trim those unruly whiskers, it's best to leave them alone.