Sudden movements, such as a child riding a bicycle past a dog, may trigger the dog's hunting instincts causing them to bite. The strong bond dogs form with owners can cause them to become overly protective. Dogs have attacked children in play if one tackles the dog's owner and the dog perceives it as a threat. Other dogs become territorial of their yard or house. On walks, a dog may be friendly, but once at home, some become aggressive to the same people previously tolerated.
Some dogs tolerate very little before they become aggressive.
Hopper said some experts think dogs don't regard small children as they regard adults. To prevent trouble, dogs should be taught their position at the bottom of the family social ladder. Children should take part in the dog's training and discipline to enforce their authority over the dog. In many cases, neutering the dog or using hormone therapy can suppress aggressive behavior. Other times, dogs can be simply kept away from situations which cause aggressiveness.