Why do dogs sometimes eat shit? Well, believe it or not, they eat shit (of a fashion) for the same reason you do: both dogs and humans are programmed by nature. As Derek Mead explains over at MotherBoard:
The question then is: why eat shit? I mean, we can’t all be eating organic quinoa salads and Purina One (that’s the fancy stuff) all the time. But it does seem weird to have abject cravings for such terrible food all the time. As always, evolution plays a role.
Thanks to the laws of thermodynamics and bioenergetics, no biological system can ever be 100 percent efficient, including digestive tracts. That means that, of all the nutrients that go into something’s mouth, some of those nutrients will come out its rear....
Neolithic agricultural revolution (PDF), during which humans began to switch from being hunter-gatherers to farmers and herders, only occurred around 12,000 ago. Our modern diet has only really been around for at most a couple hundred years, and has fundamentally changed in even the last century, thanks largely to the increase in use of refrigeration systems.
Humans and dogs now have access to a nigh-unlimited stream of food but our physical centers for taste (tongue, brain, etc.) haven’t had much time to evolve beyond our former food-stressed lives. When we were stuck searching for food all day, our omnivore selves ate a lot of leaves and berries because they’re easier to catch than a juicy, meaty creature. Cravings can be a weirdly logical thing, as evidenced by some of the absurd things eaten by pregnant women. It’s like your body says: “The baby needs something found in sauerkraut and Sriracha. EAT A PINT OF BOTH.”
At their core, cravings have been shaped to fit our past food circumstances. Salt and calorie-dense fat were hard to find but incredibly valuable. When we found some, we pigged out, like we see now in nature when predators stuff themselves silly. It’s a basic concept: if something’s rare and essential, we’ll take it however we can get it, and our tastes will evolve to entice us to do so.
....The dog eating his turds most likely doesn’t see it as gross, at least not in our sense of the word. Rather, that poo nugget is a nutrient-dense plate of leftovers.
So next time you are scarfing down a big greasy, salt-laden chunk of meat, or a fat and sugar-soaked bowl of ice cream, just remember that you are biologically programmed to eat your shit every bit as much as your dog is programmed to eat his shit.
And if you think the dog needs to stop eating his sheet, well then maybe that's also good advice for you to stop eating so much of your shit too! Something to think about as this nation heads past a 25% national obesity rate.