Predatory or chase aggression
Predatory or chase aggression occurs when a dog finds an outlet for its desire to chase by running after unsuitable moving objects. The prey can be cats, squirrels small dogs. In the absence of prey animals, and without adequate opportunity to orient their desire to chase onto a toy, dogs may run after other fast-moving objects, such as joggers, cars or people on bicycles. Dogs especially prone to this are those from the herding breeds or hounds, which are particularly stimulated by movement.
Usually the chase is enough in and of itself and the dog will pull up if the creature stops running. However, not many animals can be chased without becoming frightened and this usually means that they try hard to evade capture, making the chase more exciting. If an inexperienced dog catches up with a fleeting creature, it will often pounce on it to stop if from running
Once caught, frightened animals tend to become aggressive, and this only needs to happen a few times for the dog to learn to bite first as it catches up with its quarry to save itself from being attacked. Dogs will rapidly learn to nip the legs of joggers, attack little dogs in the park and cats in the yard.
Prevention involves socialization, control and orienting your puppy's desire to chase onto toys. Never give a puppy unsupervised access to prey animals by allowing him to stray or to wander far from you when out on a walk. Develop the chase recall so that should your dog unexpectedly set off after something, you can call him back. Remember that dogs are often closer to their wild ancestors than we like to think, and they should never be left alone with small pets, such as hamsters, or rabbits.