Shelter Dogs: Taking the Dog's-Eye View

i-83feba9bb2fe7bb3634aa18d59d4ffbf-shelter_dog.jpgAt least one dog can be found in forty percent of US households, and forty percent of those owners allow their dogs to sleep on their beds. To put this in perspective, in a family with five children, two of them can be expected to become dog owners, and one of them will probably allow the dog to sleep on his or her bed. In an undergraduate lecture class of two hundred, eighty of those students come from homes with at least one pet dog. So as you might expect, dogs are a big business! In 2007, the pet industry was worth about $40 billion in the US, with dogs responsible for the largest share of that expense.

As well as providing pleasure and comfort, though, dogs can also be a source of pain and distress to humans. In the United States, dogs bite around 4.7 million people per year. In fact, by age twelve, an average American child has a 50% chance of having been bitten by a dog. In that same group of two hundred undergrads, one hundred of them have probably been bitten by a dog. Each year, around 2 million dogs are destroyed terminated executed euthanized killed in shelters.

We often refer to the domestication of dogs as artificial selection, because at some point in history humans began intentionally hand-picking individual dogs, on the basis of a anatomical or behavioral traits, to mate. But from the perspective of the dog, this selection isn't anything other than natural. Taking the dog's-eye view, humans are just another source of strong selection pressure, and (to oversimplify the process a bit) those dogs who have the most successful variants of a handful of genes are the ones who will reproduce and propagate those characteristics.

The question that I wish to consider is this: is a significant portion of the two million shelter dogs killed each year simply the individuals with the lowest adaptive fitness? Do they end up in shelters because of significant aggression or other behavioral problems? Are they, essentially, failed pets?

I am not being cavalier about this, and do not intend to blame this enormous problem on adaptive fitness. I am sure that just as many dogs end up in shelters as a result of failed ownership as they do because they fail as pets. And of course there are some who simply escape from homes or backyards. Even if the proposed hypothesis - that shelter dogs are failed pets - accurately reflects reality, it is always important to remember that biology is not destiny. I am just thinking out loud, and looking for insight, feedback, and opinions.

Public service message: if you are thinking about adopting a dog or cat (even though they're evil), please consider rescuing one from your local shelter or rescue foundation.

Added: While it is true that dogs who wind up in the shelter and are killed might not have passed on their genes, and dogs who wind up in the shelter and get adopted out are generally spayed/neutered and might not have already passed on their genes, this doesn't explain how the dogs get to the shelter in the first place. Certainly there are many factors entirely unrelated to the temperament of the dog, that contribute to this problem, a huge one being failed owners. The question I'm attempting to unravel here, though, is: are there certain traits that, across the population, makes a dog more likely to wind up in a shelter? And if so, what are those traits? Obviously, it isn't a case of "nature" or "nurture," but both things in unison. It is still, however, useful to consider all the various angles of the problem, if for no other reason than as a mental exercise.

Statistical data from: Wynne, C. (2009). Editorial. Behavioural Processes, 81 (3), 355-357. DOI: 10.1016/j.beproc.2009.04.007

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I don't know that a dog which has been surrendered for aggression could be considered a "shelter dog" since it wouldn't be sheltered for re-adoption, but more likely killed immediately.

I'm also not sure that we can consider shelter dogs as failed selection due to traits in the dog that mark it for extinction.

There are several reasons for this, one being that animal shelter populations are largely driven by economic considerations. Loss of jobs in an area and national disasters are correlated positively with shelter population. The traits of the individual dogs have very little to do with whether or not they end up selected out.

Another reason would be that the dogs that are selected to be saved or become pets generally leave the shelter spayed or neutered, which might indicate that the very dogs with the most desirable traits are not able to pass those traits on to the next generation.

Kate: You're right - its clearly a complicated problem with many variables. And, you're right that most dogs that leave the shelter are neutered or spayed - but I don't think that helps address the problem of why they get there in the first place.

That is a thought provoking perspective. I think there is something to it, but one has to come to some sort of distinction between "failed pet" and "failed owner". Lots of pets get abandoned because owners simply can't (or won't) keep them... at least sometimes because of circumstances the owner really can't control. Once you've made that distinction though, it would be interesting to guesstimate some stats to get a sense of the selective pressure against "failed pets".

My guess is that it is probably pretty low. Many if not most owners will not be willing to give up their pet even if it is clearly poorly suited to being a pet.

A more significant issue for me is the warped selective pressures humans put on pet species and the often horrendous side effects those produce. Breeding an animal species based upon a few superficial traits is just cruelty IMO. The Victorians really deserve the blame, but we hold onto their practices.

In contrast, selection based on complex functional traits (as opposed to something like flatness of nose or coat color) is more than fine. Working dogs which are actually bred for the ability to successfully do some complex tasks are a marvel, but often don't make great pets. There is some specific breeding for "good pet" being done now, but most pet breeders are still selecting for Victorian appearance traits using highly inbred lines... a practice which is all but guaranteed to result in bad side effects.

By travcollier (not verified) on 13 Sep 2010 #permalink

Just as evolutionary biology/psychology suggest that we haven't adapted to realities of an industrial (let alone post-industrial) life, I think it likely that dogs have not adapted to this modern world either. Any number of labs/lab mixes, shepherds/shepherd mixes, etc end up in shelters because they are too high energy for their owners. A few generations ago they would have been working dogs helping out on a farm, but we keep them in subdivisions on postage stamp sized lots or (worse yet) in apartments with 2 short walks per day. They can no more adapt to that then we can adapt to the massive amounts of sugar and fat available for our diet.

Perhaps, rather than failing in some way, the ones in shelters are the ones who, 100 years ago, would have been exemplary, while the ones that are lazy and sedate enough to handle our lifestyle now would never have made it then. (Also just thinking out loud.)

Rebecca-- Why is having a dog in an apartment a bad thing? Why in gods name would you say something like that on a post that specifically points out millions of dogs are killed every year because shelters cant find them homes?

I have a very high energy pit bull who, quite happily, lives in my apartment. We go on two walks/runs a day, and play play play when Im at home. His buddies come over to visit (Germie/Rottie mix, weenie dog) and though I dont have a yard, they wrestle in my dog-proofed living room. He is currently sleeping on the sofa with his feet up in the air.

Where there is a will, there is a way, and I wont let you discourage willing people from adopting dogs for no apparent reason.

Also, this post of mine is relevant to your weird comment. Dont take that as an invitation to comment there, though, if the comment you left here is representative of your caliber.

On topic-- Arnies personality saved his life, no doubt. It was love at first sight with me, and he was skin and bones and butt-ugly when I found him on the street. But hes fixed. Dogs in shelters are too. So, so much for evolutionary anything.

I am a dog trainer and behaviorist. I can tell you that 98% of dogs who end up at a shelter (at least those that have been surrendered due to behavioral issues), and who are ultimately euthanized, are NOT there because of any innate inferior genetics.

It's almost always the owner's fault. A dog's first 4 to 5 months of life can determine their behavior for the rest of their life. If say, a puppy is undersocialized during this "critical socialization window," they will most certainly grow up to have fears and phobias that can, for instance, manifest as aggression. (most canine aggression is tied to fear, and many fears are a product of undersocialization) Something as simple as not allowing your puppy enough OFF LEASH play with other dogs can lead to ON LEASH aggression and reactivity that comes out at around 1-2 years of age. Or take potty training.. most owners are just unreliable or not committed enough to taking the time necessary to do it right. I also see a lot of cases of impulse puppy purchases, where the owner is completely unprepared and unable to deal with the responsibilities, developmental challenges, and exercise requirements that come with owning a dog.

Combine that with Ceasar Milan, and the like, brainwashing the population into thinking that his methods make for emotionally healthy animals, and you can EASILY "ruin" an otherwise great dog.

Having said that, I have also seen cases where the owner does everything right, and serious behavioral issues still arise. That is more of an exception than a rule.

Rebecca (@4): In the broadest sense, you're right in that some dogs may have been more adapted to a lifestyle that is different from the one that most dogs live in today, at least in the US. However, this is the way natural selection works - environmental pressures change, and accordingly, which individuals have higher fitness also change.


I got Arnie well after he was 4/5 months old, and he was clearly being taught how to fight. Cesar Millans show was priceless help for me-- someone who had never owned a pit before, loved him desperately, but was terrified he would grow up to be a 'bad dog'. Milans advice is basically exercise, discipline, and affection.

Again, where theres a will, theres a way...

Weird comments on this post...

Most of Milan's advice may be decent, in broad strokes. But his explanations for behavior are, in my assessment, wayyyyyy off.

@ERV - I'm fascinated how you dismissed my entire comment based on two words. Do you alway engage in such ad hominem attacks? If so I can probably pass on reading your blog entirely.

I commend you for taking on an ex-fighting pit and for providing him the exercise and interaction he needs. I'm sure your dog is happy and well-loved. But many dogs end up in shelters because people adopt the cute puppy and then freak out when the puppy turns into a young dog that eats the sofa, jumps on visitors, and engages in other inappropriate behaviors due to too much energy and no way to burn it off. Either they turn the dog in to a shelter or a rescue or they kick the dog out the door.

There are many types of dogs who are completely appropriate for apartment life and I encourage everyone to adopt a dog with an appropriate energy level for their lifestyle and a temperament that works with theirs. But refer back to your own post; Cesar preaches EXERCISE first, in part because way too many american dogs don't get enough. We walk our dogs (a rescue rottie who came to us with aggression issues and a rescue shepherd mix) past several yards that contain dogs who I have never seen walked or taken anywhere. If 40% of households have dogs, there should be far more people out there walking their dogs than I see, and that energy has to go somewhere.

@Jason (7) natural selection takes time to work. My point was that the state of the environment has been changing so fast that evolution doesn't have time to catch up, leading to those selected against ending up in shelters, getting fixed or killed. It certainly speeds up the process, although I'm unclear on whether that is a good thing. It certainly has a high cost in the meantime.

Although owners play some (probably large) part in the "success" of a dog as a pet, this is presumably distributed randomly across dogs of all dispositions. If dogs of a certain disposition are more likely than others to wind up in a shelter and be killed, there's presumably some mechanism for selection, even if it's only incremental. It's a statistical thing, and there theoretically only needs to be a small difference in fitness for selection to happen over time. An example: a drought won't only kill animals who are poor at storing water, but animals who are very good at storing water will have a probabilistic advantage over those who are not in terms of surviving droughts. Over time, if droughts happen regularly where the animal lives, the species will change.

TL;DR - you can't think about individual animals, when you're talking about selective pressure, you have to think about patterns.

That said, do dogs that are going to breed usually breed before going into a shelter? It doesn't seem like the "failure" of some dogs as pets, even if it's associated with their genetics, would come before reproduction reliably enough for this to be a mechanism by which the pet population evolves. At this point, breeds are maintained by breeders who breed mostly for morphological characteristics, not behavioral ones (although the two can be linked.) Other people breeding dogs are probably doing it more randomly or accidentally. It seems like we'll select against detrimental behavioral attributes in the pet population (like extreme aggression) but otherwise will stay pretty similar, behaviorally, as we're probably not really selecting for good social skills any more (this having been done in the past.)

As an aside, I'd like to point out that, for the obvious reasons as mentioned in this post, I view the breeding of any animal for the pet industry as immoral. Animal breeders often claim to be "responsible" breeders, and warn shoppers to only buy from such "responsible" breeders. Nonetheless, the animals they produce fill spots in people's homes that could be filled by animals that already exist and are in need, and some percentage of the animals they produce will end up homeless and/or mistreated. It is blatantly irresponsible to displace animals that could have homes by creating more animals.

Also as an aside, my fiance and I have two pet rabbits (a male mini-lop and a female dutch) that we got from a shelter, both of whom had been strays. They live in our kitchen (it's the only bunny-proof place in the apartment) and are absolutely wonderful.

BTW, Jason, I think that means I agree with you although for a different reason. The dogs have the lowest adaptive fitness not because of anything about them but because what they are being asked to adapt to is changing too fast for the species to keep up with. Adaptation takes many generations and shelter animals are those who are failing to adapt to a lifestyle that never existed before. And who were unlucky enough to end up with humans without the skills to help them.

Right, Mike (@11), of course selection operates over populations not individuals, so it was perhaps not the best analogy to use.

Even still, however, certain behavioral traits that exist in some percentage of a population could result - in general - in a dog becoming a "failed pet."

In any case, when I wrote: is a significant portion of the two million shelter dogs killed each year simply the individuals with the lowest adaptive fitness? Do they end up in shelters because of significant aggression or other behavioral problems? Are they, essentially, failed pets? I did not mean to suggest that all three questions were different versions of the same question. I think all are different ways of getting at an underlying problem from different angles.


Maybe people's attachments prevent a bias from appearing in the incoming population of shelter dogs, but the dog's demeanor should matter more in terms of them being adopted.

I've only been to one animal shelter recently, so maybe I'm not the best judge, but what I saw were mostly monsters. So I'm not so sure that there isn't a bias on either end.

I'm still missing something. If successful dogs are spayed or neutered, and unsuccessful dogs are euthanized, isn't an essential component of adaptation (namely reproduction) missing?

How does this then qualify as an evolutionary process when we're really only talking about the short term (lifetime) success of individuals rather than successful strategies for reproduction?

What point am I missing here?

Wait a second. The fact that we have so many dogs that we have a need for shelters and euthanasia really means that dogs are an overwhelming evolutionary success, right? The same way that the need for kangaroo culls in Australia is a symptom of that species' evolutionary success?

The only reason that this is a *problem* in our estimation is that we have a moral objection to needlessly killing animals, particularly ones with which we as a species have so strong a bond.

I think that what we would consider a successful dog-human relationship has little to do with dogs' evolutionary success. We would like the number of dogs in existence to be as close as possible to the number of dogs demanded as pets. Overages in dog populations are both a financial burden and a moral one, which is why limiting dogs' evolutionary success (by spaying/neutering) is so important. Evolution cares little about an organism's quality of life--it cares only if the organism lives long enough to pass on its genes.

By David Lukas (not verified) on 14 Sep 2010 #permalink

Fascinating question, Jason, even if it's not a popular one.

I also wonder what human traits among dog owners correlate with giving a dog up. I'd guess that the characteristics of the owner play at least as big a role as any traits that belong to the dog.

Shelter populations vary geographically, sometimes significantly. That's why numerous New England shelters and rescue groups bring dogs up from the south. In areas where pet neutering is culturally the norm, the populations at urban pounds tend to lean towards pitbulls/rotties. I've seen it to be true in western Mass. In the south, neutering is not the norm, perhaps due to cultural differences, perhaps poverty, perhaps a combination. You get a much wider range of breed mixes in the south, and in much larger numbers.

As folks mentioned in comments above, the economy can have a huge influence on whether people can keep their dogs. Quoting a friend who works with rescue groups in Louisiana: "...the Plaquemine Parish animal control facility had 17 owner-surrenders in June 2009. For June 2010 it is 117." That's an effect of the BP disaster putting fisher folk (many of whom live on their boats and who keep one or two dogs) out of work.

This article provides data from a study done by some Purdue University scientists--
As we might naturally suspect, a large percentage of dogs surrendered to a shelter (as opposed to strays) were given up because of a lack of training. People unable or unwilling to invest in veterinary care and training easily give up a dog when his natural tendencies overwhelm them. Dog ownership requires commitment of many resources, including money and time. Many people are clueless. I find it interesting that barking and hyperactivity are major reasons for surrendering a dog, but aggression to people is pretty small. The dog is being a dog. . . and people aren't good at working with that.

I think that for the most part, Cesar Milan is right: most dogs don't have problems -- it's their owners who do and when the manner in which they're related to changes, they change. Where he's had dogs that do have problems, it's quite instructive to see how much patience and experimentation he'll try to gain insight into how to help them. His behavioral theory... well, it's clear he's never taken any lessons.

It's a tough question you've asked as there are many confounders but nevertheless it's definitely one worth investigating. Some indication may come from the world of working dog breeders. Amongst people looking for dogs to actually *do* something like herd, hunt, guard, detect, the average dog, even if a wonderful pet is simply unsuited. Many breeders of useful dogs consider it bad practice to place a good prospect in a home that's looking primarily for a companion animal.

Perhaps a good place to start would be with a numerically abundant breed that shows divergence between companion and working animals (take the German Shepherd Dog or Labrador Retriever for two), assess whole litters at given ages, take some DNA samples and follow up at various ages to see if there's a marked difference to be found.

True, breeders and subsequent owners recruited into this investigation will be more vested than the average owner in understanding and putting effort into good ownership but this isn't necessarily a bad thing in that it also gives an insight to what sort of effort it takes to keep dogs of different temperaments happy (that is if there is a difference).

If there are clear differences to be found and there are any genetic markers, then it gives some basis to know what to look for in the shelter population, whether it's interviewing ex-owners or looking. An interesting place too will be a low-kill shelter: one that doesn't put animals down after a given time period but rather makes assessments on how readily an animal can be placed. Time taken to adopt and the profiles of healthy dogs considered for placement or slaughter would be very interesting to look at.

Of course funding such a study could also be a little challenging, but it could be very interesting indeed.

n the broadest sense, you're right in that some dogs may have been more adapted to a lifestyle that is different from the one that most dogs live in today, at least in the US. However, this is the way natural selection works - environmental pressures change, and accordingly, which individuals have higher fitness also change.