Why do wet dogs shake? Biologists discover the neural mechanism behind this hairy mammalian tactic

A team of neurobiologists at Harvard Medical School’s Howard Hughes Medical Institute has uncovered the neural mechanism involved in the unique way hairy animals such as dogs shake themselves when wet. In their study published in the journal Science, the group applied oils to the necks of mice while looking for a response from several mechanosensory neurons.

Prior research and anecdotal evidence have shown that when animals such as dogs and bears get wet or need to remove irritants from their skin, they shake themselves in a unique, undulating fashion that effectively flings water from their coats into the air around them. The research team noted that the neural mechanism behind such shaking has not been studied and was therefore unknown. To learn more about the behavior, they conducted experiments in which they tested stimuli on wet mice, which shake themselves in the same manner after getting wet.

Initial experiments involved applying several types of stimuli to backs and necks to learn more about what sets off the shaking behavior. The research team found that in addition to water, the mice reacted to puffs of air or oils applied to the back of the neck. They used oil applied to the back of the neck as an irritant in follow-up experiments.

Suspecting that reactions to stimuli that set off shaking were due to mechanosensory rather than automatic responses to changes in temperature, the team removed the Piezo2 gene in test mice and found that doing so stopped them from shaking. The Piezo2 gene is known to control ion channels involved in the sense of touch.

They next measured the responsiveness of three mechanoreceptors, testing several mice by stimulating them with oil. One receptor, called C-LTMRs, consistently led to shaking when the mice were stimulated. They also found that removing it led to a substantial reduction in shaking.

The researchers then created a map showing the path sensory signals took during stimulation from the skin to the spinal cord and then to the brain. The result was a complete outline of the neural mechanisms involved in what the team describes as “wet dog shakes.”

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