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| Earth on Dec 28, 2012

How fast can a wet dog shake dry?

Researchers have found that furry mammals can shake themselves 70 percent dry in just a fraction of a second.

If you’ve ever given a dog a bath, you probably know firsthand that a drenched dog can shake a lot of water off – fast.

Photo credit: carterse

In fact, researchers at the Georgia Institute of Technology have found that furry mammals can shake themselves 70 percent dry in just a fraction of a second.

The researchers used high-speed videography and fur particle tracking to analyze the shakes of 16 species – including dogs – at Zoo Atlanta to better understand the mechanisms of how furry animals are able to shake water off so efficiently.

Mammals with fur, unlike humans, tend to have loose skin that whips around as the animal changes direction, increasing the acceleration. That’s crucial to shaking success, said the researchers. And shaking success, they said, is crucial for the animal’s body heat regulation. That’s because wet fur is a poor insulator, causing an animals to lose heat quickly and zapping its energy reserves. For a wild animal, staying dry in cold weather is a matter of life or death.

Small animals may trap substantial volumes of water in their fur for their size. For example, when emerging for a bath, a person carries one pound of water. A rat, however, carries five percent of its mass and an ant three times its mass.

The researchers found that shaking frequency is a function of animal size. The larger the animal, the more slowly it shakes dry, Hu and Dickerson said. For example, a mouse moves its body back and forth 27 times per second, but a grizzly bear shakes four times per second. The tinier mammals can experience more than 20 g’s of acceleration.

Understanding the physics of the wet dog shake, the researchers said, could have practical applications –from more efficient washing machines,dryers, painting devices, spin coaters and other machines, to improved functioning for robotics – like the Mars Rover, which suffered reduced power from the accumulation of dust on its solar panels.

The research was published in the Journal of Royal Society Interface.

Read more from Georgia Tech

Photo credit: Bruce McKay

Photo credit: Soggydan

Bottom line: Researchers at the Georgia Institute of Technology have found that furry mammals can shake themselves 70 percent dry in just a fraction of a second.