The Science of the Wet Dog Shake

Scientists have finally decoded the mystery of the infamous wet dog shake! Kelly Ryan of the Herald Sun reports:

It’s not the length of the hair, it’s the size of the hound that determines how fast it has to shake to get dry.

Scientists have worked out the optimum amount of shaking that dogs and other animals have to do to dry themselves after a soaking.

Perhaps surprisingly, little dogs have to whip the wet off their coats faster than larger dogs to get just as dry.

The “Wet Dog Shake” theory was put to the test by researchers at the Georgia Institute of Technology.

Filming their study in slow motion for a physics video contest, they cleverly captured various animals, including a wet mouse, shaking faster than the eye can see at 27 rotations a second, to a big, grizzly bear who can complete the same task with just four oscillations.

Water sticks to an animal’s fur and only shaking gets it out. The US team used a mathematical model to work out the optimum speed at which the animals had to shake to release the water, based on the frequency of oscillation. They measured the surface tension that bound a water drop to hair and the force needed to pull it away.

But the amount of loose skin also affects the speed at which a bedraggled creature can fluff up again. The more the skin moves, the more water is expelled as the animal shakes…

[continues in the Herald Sun]

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