Who hasn’t laughed at the wet dog shake? Phydeaux comes out of the pool and reflexively performs this elaborate dance, spin-drying herself from head to tail. It wasn’t so funny when Beethoven did it in the bedroom. We’ve all learned to stay clear of this canine waggle dance unless wanting to get soaked.

Bears Do It, Dogs Do It

The wet dog shake is common to furry mammals. Grizzly bears do it. It’s been observed in “mice, rats, cats, goats, sheep, lions, tigers, bears, and giant pandas” — some 30 mammals. We humans can’t do it nearly as well (try it and see). We reach for the beach towel instead or perform a poor imitation of the Funky Chicken. But the Wet Dog Shake App comes pre-installed in most hairy mammals.

Enter science to explain the Wet Dog Shake: Science Magazine, that is, which published work by Harvard neurobiologist David D. Ginty and colleagues. Naturally, scientists must have an acronym: WDS, for Wet Dog Shake. Clever. The Editor’s Summary states,

Wet dog shakes (WDS) define a widespread behavior in hairy animals that is used to remove water and irritants from hairy skin. However, the mechanism triggering WDS remains to be fully elucidated. Using optogenetics and behavioral protocols, Zhang et al. showed in mice that WDS are triggered by Piezo2-mediated activation of unmyelinated C-fiber low-threshold mechanoreceptors synaptically coupled with spinoparabrachial neurons. The identification of this pathway shines a light on a common shared behavior in hairy animals. [Emphasis added.]

The science media loved this. Each institution posted its own story, complete with its photo of a dog in the midst of the shake, jowls and ears a-flopping, fur flying, and water spraying out in all directions.

• Nature News: “Why do wet dogs shake themselves dry? Neuroscience has an answer.”
• New Scientist: “Why hairy animals shake themselves dry?”
• The Scientist: “What Drives the ‘Wet Dog Shakes’ Reflex in Furry Animals?”
• The Harvard Gazette: “Ever wonder why your dog does this? “

Watch the opening slow-motion video in the title of that last one. The golden retriever appears in a state of bliss doing the WDS. Notice the beautiful spirals made by the water droplets — a form of biological art. This kinetic artwork is physically tuned for functional effectiveness. Faye Flam at Phys.org called it amazing, based on experiments by David Hu at Georgia Tech.

When a wet dog shakes himself dry, he does something amazing. He hits just the right rhythm to maximize the drying effect with minimal effort. The seemingly casual jiggle imparts enough centrifugal force to expel 70 percent of the water in his coat in a fraction of a second.

That percentage undoubtedly climbs when the dog repeats the shake several times. This factoid is worth sharing with the kids. The family dog’s got rhythm! It knows instinctively what to do to get dry quickly and avoid hypothermia. 

Did Science Really Explain This?

The researchers did some laudable science. Working with rats, they learned how to trigger the WDS with droplets of sunflower oil or puffs of air on the necks of the rodents. Then, they identified the sensor in the skin that triggers the shake. Using optogenetics (fluorescent tags on proteins), they found one particular mechanosensor that was responsible: a “C fiber low-threshold mechanoreceptor (C-LTMR)” that is located near hair follicles. But this point should be noted as a wondrous thing that shouts “intelligent design,” not evolution. The Harvard press release says,

The skin has approximately 20 different types of sensory receptors, including those that detect hot, cold, itch, and touch. Twelve or so receptors detect different types of touch, from a quick stab of pain to vibration to steady pressure to a soft caress. The signal triggering the “wet dog shake” starts in C-LTMRs, or C-fiber low threshold mechanoreceptors, which wrap around the base of a hair follicle. The receptor is one of the body’s most sensitive and can pick up the slightest movement of the hair or a depression of the skin around the hair’s base.

The Scientist points out that the C-LTMR sensor is activated by the Piezo2 gene (see my article about this “biological piezoelectric effect” that converts touch to electricity in the cell). Is the WDS looking extraordinary yet? The researchers determined, therefore, that the WDS is triggered by touch rather than temperature. That’s worth knowing, but does it really explain the shake itself? 

While the media congratulate the scientists and move on to the next news item, we design advocates should stop and say, “Wow!” Twenty different kinds of sensory receptors cover our skin and the skin of the family dog — 12 of them for touch! One of the body’s most sensitive receptors on the dog’s skin feels the touch of water or the touch of an irritant, triggers a cascade of irreducibly complex genes, enzymes, and ion channels, and sends the message to a particular brain region: “Initiate the WDS!” A program is executed, triggering the dog to perform an elaborate dance that sends at least 70 percent of the water off the skin. 

Is This Not Marvelous?

While appreciating that the team identified the specific receptor that triggers the response, we should realize that the biggest part of the story — the functional and artistic shake — was not explained at all. And we should feel disappointed, perhaps a little miffed, that the stock response for what led to this marvel is evolution. “Wet dog shakes are an evolutionarily conserved behavior observed widely across hairy mammalian species,” the authors say. Oh please.