Dogs are an incredibly diverse group of animals.
The American Kennel Club currently recognizes 189 different dog breeds, while the leading international authority – the Fédération Cynologique Internationale – recognizes about 350.
Yet despite this amazing diversity, every one of these breeds – from Chihuahuas to Irish Wolfhounds – belongs to the same species: Canis lupus familiaris*.
Humans are responsible for most of this diversity.
When left to their own devices, feral dogs generally become tan, vaguely shepherd-like dogs within a few generations – the Internet Center for Wildlife Damage Management characterizes the look as that of a “generalized mongrel“.
However, we have selectively bred dogs to suit our needs and desires for thousands of years, which has resulted in this glut of breeds.
You can imagine the process by which early breeders created the drastic variation in coats, color, sizes and shapes that we see today.
Want a dog with longer hair? Breed those that already have the longest hair. Given enough persistence, time and a little luck, you can create a long-haired breed. You could do the same thing to create bigger dogs, or smaller ones, or ones that appear to have had their faces pushed back into their skulls.
A similar process has led to the development of the various personalities and aptitudes exemplified by these many breeds. But instead of selecting dogs based on their physical appearance, breeders emphasized and de-emphasized various innate behaviors of dogs.
Specifically, they altered some of the steps involved in the dogs’ predatory sequence.
A dog’s predatory sequence is the set of behaviors that enable it to obtain food. The basic sequence for primitive dogs was as follows:
Orient – The dog aims its body and head toward the prey.
Eye – The dog locks its eyes on the target.
Stalk – The dog begins to creep closer to the prey without being discovered.
Chase – The dog runs full speed toward the prey.
Grab Bite – The dog bites the prey animal, often on the rear leg or hindquarters.
Kill Bite – The dog bites the animal in a way likely to lead to death.
Dissect Bite – The dog opens the dead prey’s body cavity.
Consume Bite – The dog eats the prey animal.
Different authorities embrace slightly different versions of the sequence (some combine the eye and stalk steps, for example), but the basic steps are not in dispute. It’s essentially the same for most carnivores, with small modifications to suit the species and its typical prey. For example, cats often employ a paw-clap behavior instead of a grab bite.
In most cases, these behaviors work in sequence – the conclusion of one behavior initiates the onset of the next. But when you alter the various steps through selective breeding efforts, it is possible to create dogs with wildly different personalities.
Take Labrador retrievers, for example.
Though initially used to help retrieve escaping fish, Labs are primarily used for hunting waterfowl (when they aren’t just being used as a tennis-ball-retrieval system). They sit patiently in a boat, wait for you to shoot a duck and then they go get it for you.
The general idea is already built into their brains – some begin retrieving by 6 weeks of age, like so:
By examining their predatory sequence, we can understand why Labs do what they do.
Labs begin the process by orienting themselves in the direction of the passing birds.
They then lock their eyes on the bird falling to the water.
But because it isn’t necessary to sneak up on a dead duck, the stalking step has been removed from the sequence. Instead, Labs then jump in the water and chase down the duck (usually only after being given the retrieve command).
The dogs then grab the duck. But from here, the sequence breaks down again.
Labrador retrievers rarely exhibit a kill bite; if they did, the retrieved duck would be mangled and unappetizing.
Accordingly, their predatory sequence has concluded, and they bring the duck back to the boat and wait to do it again. Note that the black lab in the video above briefly displays a kill bite on the bird he is retrieving, so in his particular case, this step in the predatory sequence has not been completely removed.
Herding dogs, such as the celebrated border collie, exhibit a predatory sequence that differs in yet another way.
These dogs are tasked with keeping their flock together and moving them from place to place. In carrying out these tasks, they exhibit the orient, eye, stalk and chase phases of the sequence, but they usually lack grab bites, kill bites and dissect bites. This crucial difference is what keeps the dogs from pouncing on the sheep and making a meal of them.
By contrast, terriers were responsible for reducing rodent and vermin populations. Accordingly, they not only have highly developed grab bites, but they also have very strongly developed kill bites:
As well as and dissect bites:
After all, you don’t want to shove a terrier down a hole only to have him bring a live rat back to you.
So, the next time you watch a dog breed performing some amazingly specific behavior, take a moment to realize that it is likely a byproduct of the same predatory drive that all dogs shared thousands of years ago.
* New evidence suggests that dogs are not the direct descendants of living wolves; instead, they are the descendants of a now-extinct wolf species. This may eventually lead dogs to be reclassified.