youtube/watch?v=39RYrucTvGo Whole Lotta Shakin The problem for a mammal with evolving fur to trap air to insulate from the cold, is that you need to then maintain it. That might mean having a built in comb on your tongue like a cat. Or as in the case of many furry critters, you need to develop a highly efficient water removal system. Why is this so important? Well just imagine you’re a 25kg Labrador and you’ve jumped into a freezing lake in pursuit of some waterfowl. You emerge with half a kilo of water in your coat, the insulating airspaces flooded and your core body temperature is plummeting. This is the point at which Bear Grylls rips off his wet clothes, yet again exposing his buff torso, starts a roaring fire by rubbing two pine needles together thereby warming himself and drying his clothes. A Labrador would lose 25% of his daily calorie intake if he allowed himself to simply air-dry, which is not a great survival strategy, so he evolved the SHAKE. Researchers at Georgia Tech University have used ultra high speed video to deliver a super slo-mo analysis of several species whole-lotta body shaking techniques. From tiny mice to bears the method is similar with the frequency of the shake increasing as size reduces so that the necessary force is generated to eject the water from the soggy coat. The physics gets a bit tricky but the videos are at once amusing and amazing. The shaking head gets things moving, then the whole backbone rotates, but only through 30 degrees (from 11 to one on a clock). Next the loose skin starts following but it moves at three times the speed because it is further out. Then you get this woomera or whip-cracking type effect as the body snaps back and forth with the skin and coat following from 9 till 3 on the clock, ejecting water with much force. A mouse shakes at 30 times a second and a dog about 4 to do this. The bottom line result is that a wet dog can eject 70% of the water from its coat in a mere 4 seconds. If you’ve ever stood close to your dog after washing it you’ll no doubt attest to this soggy fact!
Posted on: Tue, 01 Oct 2013 06:26:10 +0000
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