Dogs look awfully funny when they shake their toys back and forth, but there is a reason that they do it, two actually. One reason has to do with instinct, and the other reason has to do with play.
Instinctual Toy Shaking
Before dogs were domesticated, they had to capture and kill their prey to eat. Once a dog would catch his prey, he would shake it violently from side to side to kill it. The process of capturing and killing is called the “prey instinct.” Domestic dogs shake their toys because it is part of their prey instinct.
Shaking Toys for Play
According to Vetstreet, veterinary behaviorist Dr. Margaret Gruen from the North Carolina State University College of Veterinary Medicine says that toy shaking is a component of enthusiastic play for domestic dogs, and that they like the feeling of a toy swiping the sides of their face.