Shake it off: why dogs and other hairy mammals shake when they’re wet

A photograph of a golden retriever dog shaking water out of its fur outside
Credit: DieterMeyrl/Getty Images

It’s a fact of life: if you bath a dog, it will inevitably shake the water off all over you.

Now, a new study has revealed the underlying neural mechanism that triggers the “wet dog shakes” reflex seen among dogs and many other hairy mammals.

“Wet dog shakes are an evolutionarily conserved behaviour observed across mammals that serves to remove water and other irritants from back and neck hairy skin, a skin region that is largely unreachable by self-grooming or licking,” the authors of the paper published in the journal Science write.

The research, which was undertaken in mice, found a type of sensory neuron in the skin are the key players in this behaviour.

These mechanoreceptors, known as “C-LTMRs”, are mainly found in the hair follicles of the undercoat and are sensitive to low-force, slow-moving stimuli. They are also known to be involved in sensing pleasant touch, such as gentle stroking or brushing.

The researchers showed they could evoke wet dog shakes in mice by applying a droplet of oil to their backs. Optogenetic stimulation then allowed researchers to stimulate the C-LTMRs with pulses of light, which triggered the wet dog shakes in the absence of the oil droplets.

“Animals with fewer C-LTMRs exhibit a reduction in both oil droplet-evoked wet dog shakes and scratching, which suggests that C-LTMR activation may indeed evoke a tickle or mechanical irritation sensation,” they conclude.

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