The aggression cases I see the most can be lumped into two categories:
Dogs that exhibit aggression as part of a threat response or predatory behavior.
This is, by far, the most common. For a long time, we've classified this as fear, but I am starting to think that "threat response" is a much better description...mainly because we don't have to try to guess what the dog is feeling. But also because there can be a combination of emotions involved when we perceive a threat, including fear and anger. So, to try to guess which single emotion is behind the behavior is pointless when we can look at the behavior and conclude that its purpose is to make the dog/person stop their behavior or go away.
Regardless of the trigger or the target of the aggressive behavior, this type of aggression is almost always preceded by warning signs unless they have been punished out.
Threat responses usually have consistent triggers. A dog may growl at strangers entering the house, but not other dogs. This is why experts say that a dog that shows aggression toward dogs is not a risk to humans unless he has showed warnings in that context.
Predatory behavior on the other hand, is tricky. It often seems to come "out of the blue" for many owners, especially because the dog may not necessarily show other signs of problem behavior prior to an attack. Because it is not a threat response, the dog also won't show increasing warning signs like avoidance, growling, baring their teeth.
Dogs chase stuff. Cats. Bikes. Joggers. But these aren't necessarily predatory behaviors. My dog chases cats, but if they stand still and look at him, he doesn't know what to do and just barks at them. Just because a dog chases stuff doesn't mean they are exhibiting predatory behavior.
Predatory behavior is silent. No barking or growling. Predators don't warn their prey that they're about to attack.
Predatory attacks often target the legs, throat/neck, and abdomen of the victims and the wounds are deep and involve more than one bite, often with severe tearing or even missing chunks of flesh.
Attacks may involve violent shaking of the victim. Think about the way your dog shakes a stuffed toy (don't worry, this sort of play does not encourage predatory behavior). This is sometimes referred to as a "kill shake" which can break the neck of prey.
Predatory attacks are also very difficult to stop once they happen. In videos, people are seen hitting and kicking dogs to get them to release the victim. In a recent attack, the dog was hit with a hammer, a frying pan, and shocked with an electronic collar, none of which were effective.
In the majority of fatal attacks on humans, there appears to be a predatory component to the dog's behavior. Dogs involved in predatory attacks on humans appear to have a history of at least one predatory attack on other animals (Overall).
Predatory behavior also appears to be activated by a different area of the brain than the threat response. [I will update this as soon as I find my notes on which areas - I don't want to get it wrong!]
The only warnings most dogs give in these situations is that they fixate on their target before the attack. Just as your dog does when he spots a squirrel - that intense focus and stillness in the body with maybe a slight quiver of excitement before they run full speed after their target.
This fixed stare, with ears and body language high and forward, not responsive to the handler, can all be warning signs of predatory behavior.
Owners of dogs involved in predatory attacks often say their dog looked like they were having fun. If you choose to watch the videos below, you will see the body language doesn't look all that different from when your dog plays tug or chases a cat or squirrel. That's because this isn't a behavior rooted in fear, anxiety, frustration, or anger.
BEHAVIOR OF VICTIM
Certain movements or sounds can trigger predatory responses, including running, screaming, falling, and the sudden sleep/wake cycles of infants. Also, the uncoordinated movements such as in toddlers and elderly persons appear to be a trigger. This is not to place blame on the victims, but a look at common triggers in these sorts of attacks so that parents and owners of small dogs can be aware of the risks.
This is why dog bite prevention programs teach children to "Be a Tree" when approached by a loose dog, so that they aren't as likely to scream and run, triggering an attack.
Another common trigger appears to be when children or small dogs are lifted up to protect them from a dog, as the fast movement can trigger a predatory reaction.
Many dog parks now have separate sides for small and large dogs. Just about every trainer I know has a horror story about a small dog being killed at their local dog park. Sometimes this is triggered by the small dog running around the park or after it is startled and screams.
PREDATORY SEQUENCE AND BREED FACTORS
When predators hunt prey, they all follow the same sequence of behaviors:
Orient -> Eye -> Stalk -> Chase -> Grab-bite -> Kill-bite -> Dissect -> Consume
When humans began controlling the breeding of certain dogs, they selected the portions of this sequence best suited to the work they were needed for.
With herding breeds they selected the dogs that exhibited the first four traits and none of the last five. It wouldn't be helpful to have a Border Collie catching, killing, and eating all your sheep.
Terriers were selected for the full predatory sequence, since people needed dogs that were good at killing rats and other vermin.
Depending on the breed's original function, different intensities and portions of the sequence were selected for.
But, these days, many of the popular breeds that are our pets are bred more for form than function, without much consideration given to which dogs pass on these traits. I've seen herding dogs that kill squirrels, and terriers who aren't interested in chasing anything, let alone killing it.
Even when breeders do select dogs that exemplify the functional traits they are looking for, they can't guarantee those traits will be evenly distributed throughout the litter.
"There is no breed predisposition for predatory aggression. This is a pathological diagnosis that is about individual, not breed-associated behavior. Dogs of any size or breed can be affected." (Overall)
So, while certain breeds may have at one time been selected for the full predatory sequence, it is no guarantee that each individual of that breed will exhibit the full sequence, if at all.
And just because a breed was selected for fewer predatory traits doesn't mean that they were eliminated, altogether. As with any type of aggression, assuming one dog is dangerous solely because of breed is just as foolhardy as assuming a dog is safe because of breed.
A family member's purebred Labrador Retriever caught, killed, and retrieved this pheasant on one of our walks during pheasant season. Labs are not a breed typically associated with predation.
Historically, as the popularity of certain large, powerful breeds rise and fall, so do the number of fatal attacks by those breeds. So, while it might seem like we have a problem with a particular breed now, it was a different breed 30 years ago and will be a different breed 30 years from now.
While it's easy for the media and, as a result, members of the public and lawmakers to focus on specific breeds as the problem, the fact is that fatal dog attacks have always occurred and will continue to occur until we address the human factors behind fatal attacks.
This is why experts who work with dogs are against legislation that tries to ban a dog based on breed or appearance. Because once that breed is eliminated, another breed will top the list. And the human factors in fatal attacks will remain unaddressed.
One of the common factors in predatory attacks on humans appears to be the neglect of the dog, including the need for socialization from 8 weeks, on. This is problematic in any breed, but in large breeds with tendencies toward predatory behavior, it can lead to tragedy. Many of these attacks involve dogs that live an isolated existence, either at the end of a chain, in a kennel, or a back yard.
If we want to be serious about preventing dog bites and attacks, we need to look beyond breed and focus on responsible breeding, training, and dog ownership.
PREDATORY ATTACKS ARE PREVENTABLE
So, you've spotted some of these signs in your dog. What do you do?
To be clear, I'm not saying that just because your dog has killed squirrels or cats necessarily means that they are an imminent threat to children. It does, however, mean they may be a higher risk than a dog that doesn't escalate to catching and killing animals.
As long as you are aware of the heightened risk, you can be more vigilant and take the following steps, as necessary.
NEVER leave your dog alone with infants or small children. Ever. This is for all dog owners, because predatory attacks occur in even the best family pets.
Keep your dog securely contained indoors when you are gone. Dogs given free access to backyards can routinely practice predation on critters in the yard and are at higher risk of escapes (as well as theft). If your dog must have access to the outdoors via a dog door, use temporary fencing to create a smaller containment area that reduces risk of escape.
Consider using pens or fencing to create air-locks at gates and doorways. It only takes a moment for a dog to spot "prey" and bolt past you at the door.
Observe leash laws always. Your dog can hear/smell/see the "prey" long before you can and can quickly get away from you.
Dogs that have a history of injuring or killing small animals should never be off-leash in areas around children or where children might appear.
Dogs with a history of injuring or killing small animals should be muzzle trained and muzzled when on walks or outside the home.
Secure or remove your dog if you see them fixating on a dog or child, especially if you have a hard time redirecting their attention.
Training should involve positive reinforcement for leash manners, name response, and voluntary attention around distractions.
Never trust that your dog's training is 100% effective at preventing predatory attacks. Dogs are animals and instinct can always override training, regardless of methods used. The use of aversive methods to punish out predatory behavior with livestock has mixed results and should not be considered a reliable solution when the safety of others is the issue.
If these seem extreme, know that I am compelled to cover all precautions because of the nature of this behavior. Some dogs may need this many precautions. Some may not. I have had clients who would rather go back and live with the inconvenience of these precautions than live with the guilt and the changed relationship that is inevitable after their dog has killed someone's pet.
Fortunately, predatory attacks are less common than other forms of aggression, and fatal attacks on humans are incredibly rare - out of an estimated 90 million dogs in the US, there are an average of about 30 fatal attacks every year.
Are dogs that exhibit predatory behaviors bad dogs? Of course not! They are animals exhibiting normal behavior that is bad in our society. When in the homes of committed, responsible owners, these dogs can be safely managed and live long, happy lives as members of the family.
Aggressive Behavior in Dogs, O'Heare
Manual of Clinical Behavioral Medicine for Dogs and Cats, Overall
Dogs: A Startling New Understanding of Canine Origin, Behavior & Evolution, Coppinger
Handbook of Applied Dog Behavior and Training, Vol 2, Lindsay
The Domestic Dog, Its Evolution, Behavior, and Interactions With People, Serpell
WARNING: GRAPHIC VIDEOS
THESE VIDEOS SHOW EXAMPLES OF PREDATORY ATTACKS ON CHILDREN AND INCLUDE IMAGES AND SOUND WHICH MAY BE UPSETTING
Cat saves child from dog attack (no sound)
Dog grabs child in shopping mall (no sound)
This dog belonged to a self-declared "dog whisperer" who claimed to have
"rehabilitated" the dog and turned her into a service dog. The dog
attacked a second child after this incident and was euthanized by authorities.
Child attacked by dog
(Warning: Child's screams are clear in video)
This clearly shows the dog's body language both during and after the attack.
The dog is highly aroused, fixated on the child, and not releasing its grip.