The Wet-dog Wiggle

Link: http://news.discovery.com/animals/wet-dog-shake-physics.html
Author: Jennifer Vegias

There are many furry animals in the world, and though it may not seem like it, they are very smart. They have learned over time how to dry themselves after swimming or getting wet as efficiently as possible by shaking the water off at a frequency that maximizes the water droplets which fly off. Scientists have compared this process to a salad spinner because a salad spinner strips most droplets off of the lettuce. There is a particular team studying animals’ abilities to shake at optimal frequencies led by Andrew Dickerson. Team member David Hu is part of a lab which studies animals that use surface tension as a way to survive or get from place to place – for example, water striders which walk across water and ants that have the ability to link together to prevent drowning. Andrew Dickerson led many researchers to tape many wet furry mammals shaking themselves dry of all sizes – sizes from mice to tigers. No animals were harmed in the process. In experimenting with these videotapes, scientists have realized that the smaller animals shake off water a lot faster than the bigger animals. For example, a mouse shakes back and forth 27 times per second, but a big animal such as a grizzly bear shakes off water only 4 times per second. Another factor in how water is released more efficiently in their skin is how loose the skin is. By examining the videotapes closely, scientists were able to tell that the skin of a dog can move 90 degrees on either side of the spine. This means that the tighter the skin is, the faster it releases water and the more of the water it releases. It may not seem like a very interesting discovery, but if a dog couldn’t dry itself, it would have to use 25 percent of its daily calories just to get rid of the water. This would create a species that would die out very quickly, because every time the dog would get wet it would get hypothermia and it would die.

This article was interesting to me because I thought it was really strange how something as simple as shaking off water can be such an important thing for scientists to explore and how important adaptations can be for animals. I also thought the video was really well made, because it showed the difference between the different animals shaking off the same amount of water, from mice to Chihuahuas to Great Danes to tigers. This video helped me understand more about natural selection because it showed how important it really can be for different animals to have the ability to adapt to new environments and how if they don’t they don’t stand a chance in that world. Another example of this would be the dodos – when I read about the way that they went extinct I was pretty sad, but when you think about it nature just wasn’t on their side. Natural selection decided for humans and against the dodos.