Why do dogs like to kill things?

Here’s a spoilered video link:

The video shows a farmer turning over soil with a pitchfork, gradually unearthing a massive tunnel network that is home to a gazillion rats. Every few seconds, when he turns over a load of soil, a rat is unearthed and runs for its life - only to be promptly chased down, grabbed, and shaken to death by a pack of dogs.

The dogs really seem to enjoy this. They aren’t hungry, they aren’t eating the rats; as soon as they’ve killed one, they come back to the pitchfork, waiting for the next one to be unearthed.

What’s going on? This isn’t hunting, really, at least not for eating’s sake. Killing anything that moves seems counter to one’s survival, like a farmer eating his seed corn; it would seem more sensible to kill only what you can eat, leaving other prey animals alone so they can rebuild the population. So why are these dogs killing absolutely every rat they can catch?

In a nutshell it is prey drive. Domesticated dogs don’t need to hunt for sustenance, but they are still “triggered” by prey. For example, I have retired racing greyhounds - (did you realize that training the dog to race utilizes part of the prey drive?) my boy Ajax had moderate prey drive. He lived quite happily and peacefully with our cat, except for the occasional mock-pounce when he was feeling punchy. He also caught rabbits in our back yard a few times and would bring the poor broken bunny to our back door with a look of happiness and complete confusion on his face.

Wow! With so many dogs arrayed against them, those rats did not have a chance.

But a carnivore/predator in the wild doesn’t know when its next meal will be or how big it’ll be. Under such circumstances, it makes sense to eat as much as you can and “store” prey as fat to survive a period of no/inadequate prey. Also, a carnivore has no concept of seed corn. :slight_smile:

Such an instinct is not completely positive among humans (a predator species) in civilization (where food is more certain) but it’s still there. We don’t chase every animal we see, but we do crave sugars, fat, etc. for similar reasons.

An eminently sensible policy, except these dogs aren’t eating. They aren’t storing prey as fat, they’re leaving meat strewn all over the landscape. If allowed, would these dogs come back and eat all the dead rats over the next day or two? Or would they kill so many rats that they couldn’t possibly eat them all before the rat carcasses began to fester and putrefy?

Dogs, coyotes, foxes are really attracted to little animals that come out of the earth. In nature they dig for a good share of their food. This is a most basic instinct for them. When I took my bird dogs afield to run I would often flip over a piece of cardboard or plywood that was laying around. They would wait with anticipation to see what might take off running so they could bounce on it and shake it to death.

Why do people have sex? Because we enjoy sex. Why do we eat sweet, fatty foods? Because we enjoy eating them. Why do dogs hunt? Because they enjoy hunting.

Pleasure is a mechanism designed by evolution to compel us to take actions beneficial to our survival and procreation. A dog who hunts out of pleasure is, in the long run, a more effective predator than one who hunts purely out of hunger. It’s just the way they’re wired.

Pretty much all dogs like to chase things. A lot of dog breeds were developed for the express purpose of chasing down rats and other vermin and sending them to rat heaven.

Now my dog would chase them, but he would probably be more inclined to just round them up and keep them together. He once herded a baby rabbit away from our cat, and then stayed between them, not letting the cat get to the bunny, and he seemed to enjoy that very much. (We caught the bunny and took it to a safer place.)

But I think if he got a rat and I told him, “Kill it!” he might very well shake it to its death. He does that to his toys when I tell him to kill it. He would probably like that, too, although as far as I know he has never killed anything, unlike my serial murderer cats.

I just popped in to say that it took me over 2 minutes to realize they were speaking English.

(The people, not the dogs. :relaxed:)

It looks like a couple things contribute to that kind of scene… one being that those dogs have likely been trained to a certain degree (or at least experienced this kind of event before) to competitively grab the rat, kill it, then spit it out and try for another, competing against the other dogs seems to be part of it. Not to mention any particular breeding for this kind of behavior that might have occurred in previous generations.

Also, concentrations of rats like that seem pretty unnatural, and only happen due to human activity. In a more natural setting, prey species would probably be far harder to find and less plentiful, so the instinct to viciously go balls-out and kill one as soon as it appears would be beneficial. Those traits don’t get turned off when prey become unnaturally plentiful, the same as our own drive to pig out on high calorie foods doesn’t go away when we manipulate our environment to produce an over abundance of food.

When you have species that have adapted for most of their existence to a low(er) abundance of food, and you suddenly drop them into an environment very different with excess resources its not surprising to see over indulgence and what appears on the surface to be excessive or unnecessary behavior. But understanding where it came from helps to shed light on why it’s happening.

Many breeds of dog were selected for amplified prey drive, as vermin killers and small game hunters. It was a necessary part of the human economy to have dogs like this. That’s exactly what all terriers are. They have the whole package of locate->corner->kill-bite (and consume, once they calm down).

Sheep herding, as a matter of fact, is a kind of amplified and manipulated prey drive; the innate drive to gather and drive large game toward an ambush is selected for while the kill bite part is selected against.

Retrieving? the finding game and bringing it back to the pack part of prey drive selected for, the kill-bite selected against. Many retrievers emotionally cannot bite down on an animal, it has bred out of them.

Search and rescue dogs? The scenting and tracking part of prey drive.

Greyhound racing? The chasing down visible running prey part of prey drive.

Dogs who lack prey drive, in my opinion, are barely dogs at all. They are just friendly dog shaped ambulatory cushions.

I once had a pair of corgis who were an awesome rabbit-hunting team. Wish I had them today, I am inundated with bunnies.

I didn’t watch the video but it is probably the lurcher video in the UK? Those are bred, trained, professional vermin dogs. Most dogs won’t do as good a job as that.

Fish gotta swim, birds gotta fly. Did I ever tell you the story of the scorpion and the frog? :wink:

Hah! I’ve seen that one.

The dogs in the video are mostly terriers, and terriers are bred specifically to capitalize on and increase their strong prey-killing drive. And, even more specifically, to kill rats.

Yes, they’re killing for the sheer joy of it, and not for food. And they’re very efficient. I think every one of those rats died more quickly than if they had gotten snapped in a trap.

Some even more impressive ratting videos can be found by looking for “plummer terrier ratting”. A Plummer terrier isn’t found in any show ring. They’re bred purely for working, and not to be exhibited in an arena. They’re hell on rat populations.

These dogs weren’t hungry, true.

But their evolution has not prepared them for how to act appropriately when they’re not hungry, because for almost all of dogs’ evolutionary history, they’ve almost always been hungry. “What to do when you’re not hungry” just hasn’t been relevant. And so they’ve developed instincts for what to do when they are hungry, because that’s by far the most common state. And when you’re a carnivore, what to do when you’re hungry starts with “catch something and kill it”.

This is the answer - they’ve been bred over many generations for exactly this behavior.

Sort of like why dairy cows are relatively docile and produce lots of milk.

I’m not so sure about that. Even wolves are known to take a nice nap once they’ve gorged themselves. And since they are often in feast or famine mode, they need to let things “settle” after a feast.


What it comes down to is they get attention and approval. They’re doing exactly what their owner/trainer wants them to do. Who’s a good doggie?

No. They would do this entirely on their own. They are bred to kill with enormous enthusiasm as fast as possible. You can’t really train a dog to do this. You have to breed it.

For dogs, fulfilling prey drive is its own reward. No praise or cookies needed or wanted. The whole praise and reward thing is something that only is necessary when the activity is artificial, something the dog wouldn’t do on its own. Since that encompasses virtually all of the activities urban/suburban pet lovers require, it is easy to forget this. It also is the reason terriers are called “stubborn” and “hard to train”. Obedience was never a high priority for terrier breeders. Gameness and hardiness was.

Being careful to be clear that my following statements in no way relate to the debunked and recanted “Pack Theory” or “Alpha theory” or “Aggression Theory”

Warning PDF, from the original researcher that is often cited in the “Alpha” myth in popular media L. David Mech dismissing that theory.

Part of the domestication process was to (intentionally or not) select for animals which would prefer to avoid conflict over shared resources. Food aggression, toy aggression and other similar behaviors are dangerous and pretty useless if your dog helps you on a hunt but consumes the prey before you even get there.

In summary during the domestication process that consumption behavior was short-circuited, but the prey drive remained depending on bread and the individual. In some breeds like the Siberian Husky, which were left to fend for themselves in summer months by the Chachki people the prey drive is very very strong. While I am not personally the type of person who really cares about dog breeds I always take on Siberians as rescues because the same personality traits that made them good sled dogs fits in with my lifestyle.

My current husky has a massive drive for the chase but interestingly stops earlier than others and will only soft mouth any prey. But the prey drive is significant and similar to some terrier which were bread for hunting.

As a summary of normal prey drive in all carnivores (including humans except Bite is club/stab):

Find -> chase -> Bite -> dissect -> consume.

For her it is typically:

Find -> chase -> cover in slobber:

Selecting to stop that behavior between “-> dissect → consume” is the difference here with domestic dog. Unfortunately with that behavior short circuited they can be excited about yet another chase, which us humans interpreted as “liking to kill things”. It is probably more correct to think of it as that short-circuit or break in what is a critical survival behavior for carnivores to cooperate with humans effectively. Just imagine if Fido behaved like Fenris-Wolf gulping down Odin; eating fast as possible only to regurgitate the large chunks to share with you later…I doubt that wolf behavior would have survived any successful domestication (or am very grateful that it did not!!).

On a semi related side note a study to this popped up on the pop-sci sites a few months ago which claimed this type of change in behavior also may have resulted in domestic dogs being less capable of working together cooperatively without training.

Note how they call out that domestic dogs tend to try to avoid avoid conflict for resources.

The word “Terrier” comes from the Latin word “Terra,” which means earth. And the name refers to their purpose: digging up rodent holes and killing the inhabitants!

How do you think “rat terriers” got their name? Killing rats is in the very thing they were bred for.

I’m glad my name isn’t Jack Russell, then.