Is your dog a Taylor Swift fan? We all know Swift is a cat and dog fan. Your dog “shakes it off” just like her song title “Shake It Off.”
Your pal shakes off water quickly after a swim or a bath. If a 60-pound dog had to rely on evaporation alone to dry off, ot would have to spend a quarter of its daily calories to get rid of the water, according to Georgia Tech professor David Hu.
“To evaporate the water is very costly to them,” he said. “Physiologists call this the wet-dog shake. That’s why this shaking motion evolved, and it’s basically a slight variation of shivering.
“We think this has been evolving over millions of years of time to become so good.”
Mammals have fur, unlike us humans. After your dog swims in water, such as a pool, ocean or lake or is bathed, they will be soaking wet and then they will promptly shake off this extra water.
Everyone and everything around them gets a shower.
Your dog has loose skin that swings around as it changes the direction of its shake, increasing the acceleration for the shake. The shake begins with the head and continues to the tail.
This characteristic motion in mammals, such as your dog, is essential to shaking success. The nearby video shows the mechanism of your dog shaking, as well as mice and rats and even a bear. (Plus some very complicated physics equations.)
A wet coat and fur is a poor insulator, which causes animals to lose heat quickly and possibly develop hypothermia. As an animal loses heat, it also will lose needed energy.
For wildlife, staying dry in cold weather is a matter of life or death. It would be like you being fully clothed when doing a “polar bear plunge” or falling into a lake in the winter, and then had to keep on wearing the wet, cold clothes and could not dry off.
We humans, not having fur, need a towel to dry. Georgia Tech researchers found that some mammals, in just a second, can shake themselves 70% dry.
As researchers put it, imagine if you could come out of the shower and, instead of using a towel, you could just press a button and in one-30th of a second you’re 70% dry.
The researchers found that small animals may trap a lot of water in their fur for their size.
For example, when we step out of a bath or hot tub we have about one pound of extra water weight. A rat after being soaked in water carries 5% of its weight in water clinging to its fur, and an ant may have a hard time walking with water on its fur that is three times its weight.
The Georgia Tech researchers found that “shaking frequency is always a function of animal size.” The larger the animal, the more slowly it shakes dry.
They used high-speed videography and fur particle tracking to measure body sizes and to analyze the shaking of 33 mammals from 16 species, which included five dog breeds, mice, rats, bears, lions and guinea pigs.
Many animals examined were from Zoo Atlanta, and Hu emphasized that “no animals were harmed in doing this research.”
Large dogs, such as Labrador retrievers, shake four times a second while Chihuahuas shake seven times per second to get comparatively dry.
A mouse moves its body back and forth 27 times per second, but a grizzly bear shakes four times per second to dry off.
The smaller mammals may have more than 20 g’s of acceleration and thus use more energy than the big mammals to dry off.
Understanding the physics of the wet dog shake, the researchers said, could have many practical applications.
“We hope our findings can improve technology, especially in machines that rely on self-cleaning or self-drying,” Hu said.
He added as examples “more efficient washing machines, dryers, painting devices, spin coaters and other machines, to improved functioning for robotics such as the Mars Rover, which suffered reduced power from the accumulation of dust on its solar panels by shaking the dust off of these solar panels.”
So take a video of your dog in slow motion after a swim or a bath, stand back, and be amazed it helped with the Mars Rover.