Canine nutrition seems fairly straightforward. Whether it’s mother’s milk, dry kibble, or moist canned food, our domestic pets have a range of healthy and appropriate options available to them. As long as it’s on our terms, dog owners are tickled to witness the odd juxtaposition of a four-legged friend consuming human foods like pizza. We are equally perplexed to see them tuck in with relish to non-food items like rocks, grass, and feces. I have watched my dog eat red clay along the lake shore and also dig a hole in the backyard only to chew happily on the soil she’s turned over.
To humans, dirt is something we wash off our hands. To some dogs, it seems to be a desirable snack food. In humans, the exercise of such an indiscriminate palate may be regarded as an unusual taste or as evidence of an eating disorder such as pica. The inescapable truth is that dogs are opportunistic omnivores. Given the chance and ready access, a dog can and will eat anything. Though it seems pointless to expect rationality from dogs, surely there must be a hidden logic to all this. Why do dogs eat dirt?
For those of you unfamiliar with the term, let’s define pica. In humans, pica is a blanket term for an eating disorder that expresses itself as a desire to eat non-traditional and non-nutritious items. Some of the most common items people ingest receive their own names. Eating poop is called coprophagia, eating stones is called lithophagia, and eating dirt is called geophagia.
Each is considered unnatural for people to eat, but dogs are not people. Pica is considered an aberrant behavior in humans because we are supposed to know better the things we can and should not eat. Since we know that dogs can and do eat anything from coins and sand to rubber ducks and socks, is it reasonable to assign a term like pica or geophagia to them? It is a possible answer, but an unsatisfying one.
This is another bit of folk wisdom that refuses to go away. If my dog is eating dirt, one way to rationalize or attempt to explain it is to look at the composition of the soil itself. Perhaps there is a mineral found in dirt that the dog instinctively detects, finds, and consumes to supplement her normal diet. However, a study published in 2011 by the University of Chicago Press took all of these variables and rationales into account, at least in respect to human geophagia. They found that the type of clay most frequently eaten by humans has such little trace amounts of any healthful or nutritional minerals — calcium, iron, and zinc, specifically — that the supplemental hypothesis can easily be ruled out.
From the time they leave the whelping box, one of the primary instruments that puppies use to interact with and explore their world is their tongue. Puppies are curious and eager to know their surroundings; smelling and sniffing provide a nice start, but without a sense of touch linked to their paws as ours is to our hands, a dog’s mouth is an even more important mode of knowledge acquisition. If they start eating dirt and are not discouraged from doing so while young, it can become a continuing habit through life.
Of course, strange eating habits can take root at any age. For dirt-eating lifers, or puppies who express a taste for it early on, a trainer might be your best bet. Proper, consistent, and positive training methods can discourage puppy curiosity from becoming a habit or a problem. Dogs are creatures of habit, and if they become accustomed to regularity in all things — mealtimes, playtimes, rest times — and know what to expect and when, it is less likely that they will engage in activities we consider unusual or unhealthy.
Two of the most commonly accepted answers to why dogs eat things like grass, rocks, poop, and, yes, even dirt are deceptively simple. Take a look around the home, yard, or other spaces your dogs occupy while you are away at work or school. Are the dogs alone for hours at a time, left to entertain themselves? Do they have sufficient toys to play with, puzzles to exercise their minds, or living companions to interact with? We consider activities like digging, tearing into garbage bags, or barking as destructive or unproductive behaviors, but to a dog, it’s entertainment. For a dog who spends a lot of time outside, eating dirt is one way for her to pass the time until you return, a way to lessen the strain and stress of separation anxiety.
As we’ve seen, there are several possible explanations for why a dog might eat dirt. Answers are clearly in short supply, and involve inconclusive data or pure guesswork at the best of times. If clay consumption is a newly emerging habit, you can work, either on your own or under the guidance of a professional trainer, to develop strategies for discouraging pica in dogs. Should your dog suddenly and repeatedly exhibit a taste for dirt, or stranger and fouler things, after never previously exhibiting a taste for them, consult with a veterinarian immediately.
Can we ever totally prevent a dog from experimenting with non-foods? Unfortunately, the answer to this is a resounding no. On a very basic level, a dog is an inherently curious creature. Any new thing she encounters is just as likely to be licked, tasted, or chewed upon as it is to be ignored. The good news is that dining on dirt, especially if it’s freshly excavated after digging, presents little health risk. The kinds of parasite eggs that may be present in fecal matter typically remain above ground level. Unless you live next to a coal ash lagoon or some other waste disposal facility, where toxic elements may seep into the ground over time, there is little apparent health risk.
If dirt is indigestible, it presents no real danger to a dog’s health, and is likely to be passed in stool with other tiny granular refuse. Stones, rocks, or other potentially sharp objects offer greater health risks to the integrity of the dog’s digestive tract, on the way in and on the way out, than dirt does.
Does your dog have a taste for the earth? Share your experiences in the comments!
About the author: Melvin Peña trained as a scholar and teacher of 18th-century British literature before turning his research and writing skills to puppies and kittens. He enjoys making art, hiking, and concert-going, as well as dazzling crowds with operatic karaoke performances. He has a one-year-old female Bluetick Coonhound mix named Idris, and his online life is conveniently encapsulated here.