Why and how dogs shake water was finally revealed by science in 2010 - a18

It seems that science is at last trying to catch up with how the domestic dog performs many tasks. Just recently Dog Walkers Melbourne reported on studies showing how dogs drink water. The latest research into the dogs method of shaking water from their coats shows that as they have evolved to do so with the highest efficiency possible.

The core reason behind this vital action is to remove excess water from their coats so they do not get hypothermia. Scientists calculated that without devising the shaking behavior to remove the water that up to 25 percent of an animals daily calories would be required to heat their bodies. In lean times this excess energy burn would potentially lead dogs to starving to death.

The studies also show that shake speed varies depending on dog size and skin looseness. In fact there is a whole new field of dog water shaking science!


High speed videography and X-ray cinematography were used in the study to understand the physics of the dogs body movements internally and externally.

“The scientists determined that shaking begins at the head area, which provides a solid point for the energy wave to propagate down the animal's body. The head can also twist more, resulting in higher amplitude waves. Once that process starts, the animal's head, body and skin all move during a shake” (ref 1)

The body shakes at the same frequency as the skin but it cannot rotate as far. This means the skin twists further around the body and moves faster than the body and head causing a higher acceleration and higher water removal. On some animals the skin can move up to 90 degrees on either side of the spine.

Dogs that have a lot of hair/ fur often have loose skin that further assists the acceleration of the coat when the dog changes the direction of its shake.

The study also found that smaller dogs must shake much faster than larger dogs because their hair and skin is much closer to their central axis. The only way to generate sufficient acceleration of the fur, and to flick the water off their body, is to shake much faster. They have measured some of the smallest animals experiencing up to 20 g’s of acceleration at their hairs end. A G force is the equivalent of feeling the force experience of earth gravity. And so 20 Gs is equivalent of 20 times the force of gravity (where force = mass x gravity). One of the smallest creatures measured was a mouse that was found to shake itself at around 27 Hz, or 27 back and forth shakes per second! (ref 2)

To put the G force effect into perspective, on the fastest roller-coasters you may experience a maximum of up to 4G. And if you were to be in a jet and you are not a pilot (or wearing a G-force suit), most people usually black out between 4 and 6 G’s.

At the opposite end of the scale, the largest dogs and large mammals such as bears shake as slow as 4 hertz or four complete shakes per second.

You may also like to see a good video that shows various size animals including dogs shaking water from their bodies.


The studies suggest that somewhere along the evolutionary line, that most animals learned to shake at an optimum frequency to remove water from their coat. It can now be understood that while most owners hate it when dogs shake water inside their house, that dogs are just performing an automatic survival function.

The study also had the side benefit of having a commercial benefit to Whirlpool who sponsored the studies. They are using the results to assist them in building more efficient washing machines. The study may also assist the design of dryers, painting devices and spin coaters.


Article by Bruce Dwyer. If you wish to use any of this information please refer to the article as a reference and provide a link to http://www.dogwalkersmelbourne.com.au


Ref 1  http://www.msnbc.msn.com/id/40152738/ns/technology_and_science-future_of_energy/


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