What do dogs use their whiskers for?

Red fox showing its whiskersThe whiskers are specialised hairs, which are thicker than normal, and help to provide information about the dog’s environment at close quarters. These hairs are present in the dog's wild relatives, including the red fox as shown.

They are arranged in tufts, with those running along each side of the snout being the most prominent. These particular whiskers may help a dog to discover whether it will be able to slip through a narrow opening for example, while those on the underside of the jaw indicate the position of the jaw, relative to the ground. 

The presence of whiskers above the eyes probably helps to protect this vulnerable part of the body from injury when a dog is walking through undergrowth, alerting it to the presence of a low branch before contact is made with the eye beneath. The dog’s reaction time is very fast for this reason, when these whiskers are touched, frequently causing it to blink.