Deceptively simple on the surface, whiskers – also referred to as vibrissae – are part of a tactile sensory organ and serve two major functions:
1. Compensate for your dog’s poor vision and provide information about their environment
2. Convey emotion, interest, and arousal levels
Essentially–your dog “sees” with their whiskers!
Anatomy of whiskers
Whiskers might look like longer strands of the fur already covering your dog’s body, but they’re actually anatomically and physiologically different. The root of each whisker is packed with blood vessels and nerves.
Whiskers are among the very first hairs on puppies to develop, indicating their importance. In the portion of the brain devoted to processing touch, 40 percent is set aside for a map of the whiskers.
An old myth suggests that the whiskers are physically attached to the brain. While untrue, this myth has a seed of truth: the vibrissae are served by the largest of the 12 pairs of cranial nerves.
Location and function of whiskers
Whiskers can range in appearance from long, thick hairs to short bristly ones, and tend to be scattered around your dog’s face. The exact placement of them varies based on the individual. Typically, they’re located above the eyes, on both sides of the muzzle, above the upper lip, and beneath your dog’s chin. Capable of detecting subtle air currents, they provide information about what’s happening around your dog’s face.
Anatomically, these whiskers are all the same, but their location determines function. The whiskers above your dog’s eye trigger a reflexive blink when touched, protecting their eyes. Around the muzzle, the whiskers grow longer, roughly equivalent to the width of your dog’s head or body. These whiskers respond to air currents as they approach objects, allowing them to navigate in low-light conditions and compensate for their farsighted vision.
The whiskers around your dog’s lip and chin tend to be shorter than the others, but no less sensitive. The muzzle blocks your dog’s vision as they draw close to objects, but these hairs let them know just how close they are from something they’re interested in picking up. Although not studied closely, these whiskers may be sensitive enough to indicate not only proximity but also size and shape.
Evolution can be efficient–in addition to compensating for sight and providing an alternate method for touch, whiskers have a secondary function of communication.
Your dog can move their whiskers slightly upwards to indicate happiness or curiosity, or out and towards something that they feel threatened by. When your dog is relaxed, so are their whiskers!
Avoid trimming whiskers
The German, Austrian, and Swiss Animal Welfare Act bans whisker trimming for aesthetic purposes and classifies it as temporary amputation. Without the vibrissae, the sensory organ is not functional and the loss of them constitutes temporary physical damage.
A paper written by Dr. Thomas E. McGill speculated based on the studies performed on rats and mice that repeated vibrissal amputation in show dogs may cause long-term harm. Newborn mice with damaged vibrissal papillae had permanent abnormal development in the cerebral cortex. Adult rats with amputated vibrissae displayed reduced metabolic activity in parts of the brain associated with vibrissae input.
However, if your dog’s whisker has been cut or damaged, don’t worry–despite being very sensitive, the whiskers themselves do not contain nerves and are not painful to trim. Like all hair, whiskers fall out on their own and grow back slowly. Whiskers should never be plucked, as they will bleed profusely due to the amount of blood vessels in their base.