Predatory behavior can involve chasing and even biting but it's technically not aggression at all. Aggression is intended to drive a threat away or eliminate it. In predatory behavior the intent is to get CLOSE enough to the prey to catch and eat it. If you are not sure if your dog's chasing activity is related to predatory instincts or territorial defense consider the following.

	Predatory aggression is preceded by hiding, stalking or sneaking while territorial aggression is accompanied by erect ears and tail, barking and jumping around.
	Predatory aggression is silent except in scent hounds who howl when they catch a whiff of potential prey.
	Predatory aggression is usually directed at small moving targets while territorial aggression is directed at intruders, especially near the dog's home, car or owner.
	Predatory aggression is never directed at something the dog fears.

Herding and Retrieving are forms of predatory behavior. Shepherd and hunting dogs are employed for their natural instinct to surround a group of animals , select one, (herding), and catch and bring it to a safe place to eat (retreiving). Even though these are hunting skills, domesticated dogs are so unlikely to carry out a complete predatory behavior chain from finding to eating, that farmers can leave dogs alone with sheep, cattle, even ducks and families have few problems with cats, birds and rabbits. However, predatory behaviors can be a problem when targets are bicycles or wildlife. Also, herding and retrieving dogs often include nipping or mouthing in their attempts to "direct" people, which is obviously a problem.

Predatory aggression is difficult to stop because it is based on instinct. The dog does not have to think before reacting to a quickly moving cat or car. You can not teach a dog not to chase a moving object, however you can train him to respond to a competing command from you. During the training period of two months, you have to be present every time the dog sees a target and be able to carry out a deterrent for the behavior--every time. You must ensure that the dog is never exposed to the target unless you are present and within reach for the entire training period.

First, the dog must be taught to sit and stay on and off leash, with distractions. See Basic Lessons. Once this is achieved, the dog can be placed in a sit-stay on a leash and exposed at a distance to the target (cat, bike, bird) and praised for noticing but not reacting. It is critical to reward the dog with praise and treats for NOT alerting to the "prey". If you wait to reward until the dog is concentrating on the target, you will reward the wrong behavior and make the problem worse. The dog must replace what HE wants to do with what YOU want him to do. At the first sign of interest in the prey, you say "NO". If the turns his interest to you, reward. If the dog breaks the stay in any way, apply a correction with a training collar. The target will gradually be introduced while the dog is not on a commanded stay. The dog will simply be told "No" at the alert and rewarded for turning attention back to the trainer. Finally, while the dog is outdoors, off leash over the course of the two months the dog will be exposed to the target with the same goal in mind. At any sign of confusion on the dog's part, return to the previous level of success. 

An electronic collar is sometimes used in these cases so that the trainer can expose the dog to the prey and deliver a correction if the dog fails to respond to commands while the leash is off. It's important to understand that shocking a dog to teach him not to chase a cat would never work. Teaching a dog to sit and stay on command under many distracting situations, then adding a collar correction when the dog disobeys a command he knows well, and THEN switching to a remote collar so no leash is required, will help to teach a dog that he is required to respond at all times--even without a leash. The interest in the cat is still there but actual chasing is thwarted by a command the dog will obey as long as someone is there to give the command. Even with successful training the dog will not be safe ALONE with any prey target, ever. 

In some cases, a dog's predatory behavior is directed toward children. This can be a problem in large dogs because their size makes them capable of inflicting serious injuries. When children are a target of predatory behavior, you will not be able to assure the dog's safety around any children at any time. If you have any reason to believe that your dog stalks children, you will need the help of a professional trainer and a commitment to prevent rather than cure.