We all love to watch our dogs do fun things, I mean we love them. But when it comes to dealing with the weather, they are pretty darn smart – especially when it comes to drying off in the rain.
Some of the life’s most routine tasks like bathing your dogs get much more interesting especially when you get to capture your dog shaking to dry off in a high-speed camera and see how their fur goes flippity flappity as it showers everyone nearby. Well, most of you probably love a video of a wet dog shaking in slow motion. But, do you actually know the science behind why dogs shake to dry off?
In the latest video of SciShow’s “Why Do Dogs Shake to Dry Off?” Hank Green explains that an animal’s fur only works as insulation when it’s dry, and it can trap a layer of air next to the animal’s body. So, for furry animals (like our dogs) being wet in cold weather can lead to hypothermia. And in order to prevent it, evolution has honed that wild shake into the perfect quick-dry method for furry animals.
In a study conducted in 2012, scientists filmed 16 mammal species including mice, goats, tigers, and bears –at Zoo Atlanta as well as five dog breeds in all shapes and sizes using a high-speed video camera. Analyzing their video, they counted each species’ skin oscillations per second to see how they compared. They found that each species tuned its shaking speed at a particular frequency to get as dry as possible without wasting too much energy.
Force equals mass times acceleration. Or in other words, force depends on how much mass something has, as well as its acceleration. So for small species (that don’t have much mass), they would need to shake the fastest in order to generate the force required to overcome the surface tension that makes water sticks to fur. However, for large animals, their size makes it easier to generate sufficient force, and hence they move slower to reach a comparable degree of dryness.
Mice shake as many as 27 times a second, and larger animals like giant pandas can get dry just by doing a lazy 4 or 5 oscillations each second. Some furry animals are aided by loose, flappy skin too. Hank explains the way their skin whips around helps throw the water off quickly, but sometimes it generates so much force that “animals instinctively close their eyes” to prevent damage from the extreme centrifugal forces.
Researchers behind this study think that understanding how animals shake themselves dry could help them figure out a way to rapidly shed water from sensitive equipment, or even build better washers and dryers.
Well for humans, biologists think we never evolved to use that quick-dry technique because we don’t have a layer of fur that we need to keep dry. Our skin doesn’t trap nearly as much water as fur does, so it doesn’t take as much body heat to evaporate it. Hence we need not shake when we out of the shower. Hairless animals don’t shake themselves dry, too. Scientists once filmed hairless guinea pigs along with all those dogs and mice, but the wet guinea pigs didn’t shake — they only shivered.