Wet Dogs Don’t Choose to Shake – It’s in Their Genes

Have you ever found yourself caught in a flurry of water droplets as a wet dog shook to dry off? Well, it’s not a choice. Scientists have discovered the mechanism that drives dogs—and many other furry mammals—to shake off water with intense vigor. This behavior is involuntary and has fascinating genetic roots.

Discovering the Sensory Mechanism Behind the Shake

Neurobiology researchers at Harvard Medical School’s Howard Hughes Medical Institute identified the complex yet efficient sensory mechanism behind the “wet dog shake,” showing that your pet isn’t trying to punish you for that bath—it’s simply a natural reflex.

The wet dog shake is an evolutionarily conserved behavior seen across mammals, helping them remove water and other irritants from their fur-covered skin, especially on the back and neck, areas that are hard for them to reach for self-cleaning. The researchers explained that C-LTMRs detect even light forces on the hairy skin, such as water or insects, triggering motor responses that have evolved to remove water, mechanical irritants, and potential threats.

In a series of experiments with mice, scientists applied stimuli like oil and air puffs to the back and neck—hard-to-reach areas for grooming—and used high-speed cameras to capture the onset, frequency, and duration of shaking.

Probing the Brain’s Role in Triggering Shaking

Neurobiology, which aims to understand brain mechanisms that trigger behaviors, led the team to use optogenetics, genetic manipulation, and real-time calcium imaging to identify active neurons. When they bred mice without C-LTMR neurons, they saw a significant reduction in the “wet dog shake” in response to mechanical stimuli like oil and water.

C-LTMRs, or low-threshold mechanoreceptors, are sensory neurons that respond to light mechanical stimuli on hairy skin in mammals. Although researchers already knew that they activated from touch, it wasn’t clear that they played a central role in triggering the full-body shake in animals.

The study showed how the stimuli activate the Piezo2 ion channel, which regulates the C-LTMRs, connecting to spinoparabrachial (SPB) neurons and triggering excitatory postsynaptic currents (EPSCs) along a pathway controlling this motor response.

The researchers also used light to stimulate the neurons (optogenetics), triggering the shaking response even without physical contact, demonstrating that activating C-LTMRs alone can initiate the behavior.

“The finding that C-LTMRs contribute to stimulus-evoked wet dog shakes allowed us to explore how these sensory neurons engage central circuits to mediate somatosensory behaviors,” the scientists noted. We confirmed that C-LTMRs are synaptically coupled to SPNs because optogenetic activation of C-LTMR terminals produced excitatory currents (EPSCs) in both SPN populations.

A Detailed Look into the Mechanically Triggered Shaking Pathway

“These findings collectively demonstrate the role of a C-LTMR–spinoparabrachial pathway in mechanically triggered wet dog shakes,” the team added.

This might be more than you ever wanted to know about why water ends up on the ceiling after your dog’s bath, but it reveals just how complex sensory systems and behavioral responses can be. Until recently, limitations in technology left this discovery at the hypothetical stage.

So, next time your dog sprays you with water, remember they’re not trying to annoy you—it’s simply in their genes.

Read the original article on: New Atlas

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