Many mammals, including canines, have whiskers. Some dog owners think these whiskers are just longer unruly hairs that can be groomed and even snipped off entirely -- but this would be a huge mistake. The whiskers, technically known as “vibrissae”, serve important specialized functions that help dogs sense the world around them and coordinate their movement.
Humans sense touch through millions of sensory receptors that line the skin and deeper tissue. Unlike humans, the follicles of the coarse hairs protruding from a dog's muzzle, jaw and above its eyes are also packed with nerves that relay sensory information.
Essentially, these whiskers allow dogs to sense objects and the world around them as humans do with fingers.
What are a canine's whiskers good for
The tactile sensation is made possible thanks to Merkel cells, which are specialized skin receptors associated with nerve terminals. A dog's mouth and snout are very rich in Merkel cells, according to a study published in the journal Veterinary Science.
According to researchers, these tactile hairs serve a variety of functions. For instance, the whiskers allow dogs to gather information from subtle changes in air currents about size, shape, and speed of nearby objects. Ultimately, this allows canines to see their surroundings better, even in dark. It's well known that vision isn't a dog's strong point, so their vibrissae greatly assist them -- especially when dealing with close objects (dogs are farsighted). Whiskers beneath the chin allow dogs to "see" objects obstructed by their snouts.
Whisker's positioned immediately above the eyes are particularly important for vision. When an object or strong airflow causes these whiskers to flex, dogs will reflexively blink in order to protect their eyes.
It's not clear whether dogs use their whiskers for food acquisition. However, if they're anything like rats, seals, and walruses -- all related species that have been shown to use their whiskers to find food -- dogs might very well use their sensing hairs for this purpose, too.
A dog's whiskers can also serve an important role in communication with other canines or other species. Like many other mammals, when a dog is threatened it will automatically flare its whiskers, pointing them in a forward direction. This signals to predators and other aggressive animals that the dog is ready to defend itself and respond with violence.
Dogs may use their whiskers to also disperse pheromones, keep their head upright when swimming, and monitor their environment.
About 40% of a canine's visual cortex (the part of the brain responsible for processing vision) is devoted to mapping information from whiskers. They're that important!
What you need to know about your dog's whiskers
Although they might look similar, vibrissae are distinct from body hair. The main difference is that a dog's whiskers are directed by the nervous system and contain nerves.
Unlike cats, which have four rows of whiskers on either side of a cat's face, the placement of a dog's whiskers is less predictable. Some have a multitude of vibrissae, others may have few or even none. You should find them above the eyes, on both sides of the muzzle, above the upper lip (pointing down) and beneath the dog's chin.
According to scientists, there are no breed-specific differences in canine whiskers. An exception may involve hairless breeds, which have no whiskers at all.
That being said, you should never trim your dog's whiskers. Some pet owners believe their dogs' whiskers should be groomed and snip them for aesthetic purposes.
This practice won't hurt the dog, because there are no pain receptors found in whiskers. However, given the multitude of functions they serve, a whisker-less dog will become confused, disorientated, and less able to navigate its spatial surroundings. If you cut your dog's whiskers in the past out of ignorance, know at least that they will grow back naturally.
In summary, dogs use their whiskers as a sort of radar to detect objects that they cannot properly see with their own eyes.