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