You know them as “whiskers,” the stiff and heavy hairs that grow out from your dog’s muzzle and over your dog’s eyes. They are obvious on dogs that have short hair on their faces but may be hidden on dogs with mustaches and beetling eyebrows, like many terriers have. The technical name for these hairs is “vibrissae." Vibrissae actually perform a sensory function. Snipping whiskers may actually be detrimental to your dog's ability to perform some tasks.
The vibrissae are identical to ordinary hairs with the exceptions of size and depth of their roots. The whiskers are surrounded by muscle and erectile tissue, which contribute to their use in the dog's analyzing his surroundings. Vibrissae are connected to two nerves, including the large trigeminal nerve, and to a blood supply. If a whisker is pulled from its surrounding tissue, the action will result in pain and bleeding. The structure of the vibrissae causes them to be sensitive sensory structures.
Dogs apparently analyze their surroundings by using their vibrissae. These whiskers are sensitive to air currents, which cause them to vibrate. A dog then uses these vibrations to determine if obstructions exist in his immediate area, as well as their nearness, sizes and shapes. While these messages may be secondary to sight in a well-lighted area, they can be vital in a dark room or, for a working terrier, in a tunnel in pursuit of quarry. Hunting dogs that work in brush or high grass may also find the messages from vibrissae useful. No evidence exists that vibrissae are an organ of balance, though.
Vibrissae removal usually takes place at the surface of the skin when the dog is being groomed. A groomer may remove the vibrissae using electric clippers, if shaving the dog’s muzzle, or using scissors. Removal is not painful for the dog, since the whiskers’ nerve endings are far below the surface of the skin. Plucking or electrolysis, neither of which are usual practices, may cause pain because they remove the hair from below the surface of the skin. Pet groomers, as well as show groomers, will sometimes remove vibrissae; however, some breed standards now prohibit or discourage whisker trimming as the practice falls out of favor. If vibrissae are removed at the skin’s surface, they grow back quickly.
Countless anecdotal accounts exist of dogs that appear to have lost their spatial awareness when their vibrissae have been removed. These accounts are often held up as evidence of cruelty associated with removing a dog’s whiskers, even clipping them at the surface of the skin or snipping the ends. However, no recent research exists showing any serious negative effects associated with removing whiskers from an average family pet that does not spend a great deal of time in the field hunting or working. If any question exists in your mind that your dog will not benefit from having his whiskers trimmed, or if you feel that trimming whiskers is an act of cruelty, then you should not trim your dog’s whiskers.
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