Note: I’m writing this article for purely informational purposes. With any type of dog aggression, you should always consult a qualified, experienced behavior professional who will work with your veterinarian.

If your dog is aggressive, you need to become a skilled reader of canine body language. Each of these forms of aggression requires a different treatment plan, but a single dog may exhibit multiple types of aggression.

Be aware that a common thread that runs through many of these descriptions is fear –- the dog is afraid of being hurt, of having his food taken away, or he feels that he cannot otherwise get away from a threat and thus must resort to defending himself.

1. Possession aggression (resource guarding)

This is normal dog (and human) behavior. A very hungry person may smack the hand of a friend when she reaches for the last french fry on the plate. If all the humans in the world died tomorrow, the dogs who resource guarded would be the ones most likely to carry on their genes.

Resource guarding among dogs is often highly ritualized. It often looks and sounds quite scary, but causes no damage.

If your dog is actually injuring other animals, or if the resource guarding toward you or other animals is increasing in frequency or intensity, talk to a behavior professional immediately.

2. Barrier frustration

Many dogs who otherwise play well with other dogs off-leash may display reactive behaviors, barking, lunging, and growling when on-leash. Dogs who are curious or enthusiastic about passersby of the two or four-legged sort may develop barrier frustration after repeatedly being visually aroused by, but otherwise restricted from, investigating these new people or animals. This can quickly turn into aggression when combined with aversive actions like leash corrections or shocks from an electric fence.

3. Inter-dog aggression

This happens when dogs choose fighting over play with other dogs. Interdog aggression can result from inadequate socialization, traumatic experiences in the presence of other dogs (being attacked by other dogs or the owner through aversive training techniques around other dogs), or a combination.

4. Redirected aggression

This happens when a dog is held back from the object of his aggression and expresses aggression toward a nearby person or other animal instead.

5. Territorial aggression

This often combines factors of resource guarding (this place is mine!) with aspects of barrier frustration (I want to get closer to or farther away from that thing, but cannot because I am restricted by a fence or chain).

6. Maternal aggression

Most mothers, regardless of species, have an innate and hard-wired tendency to guard their progeny from perceived or potential threats. While this is frequently hormonal, it can quickly develop into a learned behavior, which lasts long after the pups are weaned.

7. Pain-induced aggression

Even a reliable, devoted, everyone’s-best-friend dog may very well bite his owner, another person, or another dog when he is in acute pain. It’s a good idea to keep a pet first-aid kit that includes a muzzle in your home or vehicle at all times.

8. Fear aggression

Fear is at the root of many of these types of aggression. A dam is afraid her puppies are in danger, an injured dog is afraid that his pain will be worsened, and a resource-guarding dog is afraid that a valuable object will be taken away. You will need to teach your dog to feel confidence in the presence of that which causes him fear through stress reductions.

9. Predatory aggression

This is directed toward small animals or large prey animals. It can also be triggered by fast-moving people or objects, including cars, bicycles, joggers, rollerbladers, or remote-controlled toys.

10. Medically based aggression

If your dog begins to display aggressive behaviors or tendencies, get him a full medical checkup, including a full thyroid panel, complete blood count (CBC), and blood chemistry evaluation, to see if anything is out of whack. Pain-induced aggression can also be seen as a form of medically based aggression.