Shakedown - How To Dry A Furry Mammal
August 20, 2012

Researchers Study The Lowdown On The Shakedown

Brett Smith for - Your Universe Online

In continuing a trend that has seen scientists looking to the mechanics of nature for inspiration, researchers at the Georgia Institute of Technology are studying the ways in which furry mammals shake themselves dry.

The study – which involved 33 different animals, including 16 species and five dog breeds - found that furry mammals can shake 70 percent of the water off their bodies in just a fraction of a second. They also saw that smaller mammals shook at higher oscillations to compensate for their diminutive radius, according to the research team´s report published recently in the Journal of Royal Society Interface.

Equipped with a hose and high-speed video camera, Georgia Tech mechanical engineering professor David Hu, along with his colleagues Andrew Dickerson and Zachary Mills, teamed up with Zoo Atlanta to study the drying technique of furry mammals that likely played a role in the evolution and survival of these animals.

“What would you do on a cold day if you were wet and could not towel off or change clothes? Every warm-blooded furry creature faces this dilemma often,” Dickerson said. “It turns out that oscillatory shaking exhibited by mammals is a quite efficient way to dry.”

The report cited two factors that play an important role in determining how these furry mammals shake off the water that is held close to their bodies by the forces of surface tension. Smaller animals had to oscillate their bodies and heads rapidly to overcome this attractive force. For example, a tiny mouse swings its body 27 times per second, but a grizzly bear does the same thing four times per second.

The skin of furry mammals, which tends to be loose against their bodies, also plays a role in getting these animals dry during a shakedown. As furry mammals oscillate, this loose skin “whips the fluid around much faster than if the skin was tight”, said Hu. This whip action increases the acceleration of water droplets on the skin–sending them flying around the animal.

Mammals use this combination of factors to generate forces between 10 and 70 times that of gravity, yet they do so while trying to expend the least amount of energy – a crucial balance that needs to be kept during the colder months.

While wetting down animals and filming them with a high speed camera provides a potentially great viral video, the researchers said they hope the study will provide a window into technology that could remove liquid or dust from machines, like the Curiosity rover that recently landed on the surface of Mars.

"We hope the findings from our research will contribute to technology that can harness these efficient and quick capabilities of drying seen in nature,” Dickerson said.

“In the future, self-cleaning and self-drying may arise as an important capability for cameras and other equipment subject to wet or dusty conditions,” Hu added.

In addition to observing live animals, the scientists built and studied a ℠robotic wet-dog-shake simulator´ that was designed to eject water from its surface.

Hu and Dickerson said their future research will center other ways animals interact with water in the natural world.