Ever wonder why some dogs seem to savor eating poop—their own, and sometimes that of other dogs? It’s understandable how upsetting this habit would be to their humans, and a team of researchers from the Center for Companion Animal Health, University of California, Davis, tried to get to the bottom of this problem. (pun intended)
Their findings were presented in their study report, titled, “The paradox of canine conspecific coprophagy.” The scientific name for a poop eating habit is coprophagia or coprophagy. The word conspecific denotes animals from the same species; so, while some dogs are attracted to stools of other species like cows, horses or cats, they were not considered. This study only focused on dogs who favored eating dog poop.
There were two surveys conducted for this study. One gathered data from both coprophagic and non-coprophagic dogs in order to compare them and the other only included dogs who were coprophagic. Roughly 1500 surveys were collected from each survey. No females who had recently given birth were included in the study because mothers typically eat their puppies’ poop even if they do not engage in coprophagy under other circumstances.
Determining the Reasons Why Dogs Eat Poop
The researchers, led by the eminent professor emeritus Benjamin Hart, posited that coprophagy is a paradox because dogs “seem to find conspecific feces aversive and typically keep their ‘den’ areas clean by eliminating outside the house.” Meaning, dogs can be housetrained easily due feces aversion. It is also one of the reasons that some advocate crates when housetraining—dogs rarely defecate where they sleep.
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Two competing hypotheses evolved about the reason dogs eat poop. One hypothesis is that coprophagy represents an abnormality because of one or more factors, perhaps dietary deficiency, a weak aversion to feces or a compulsive behavior. This hypothesis predicts that coprophagic dogs would eat differently than other dogs, that they would have been hard to house train and be more likely to exhibit compulsive behaviors such as tail chasing. It also predicts that the commercial products would help with this problem in some cases.
The second hypothesis is that this behavior is a natural one that has been passed on from wild ancestors to keep “den” areas clean and free of parasites in poop left by a sick or injured dog. (Feces that are less than two days are more likely to contain infective parasites than fresher poop.) This hypothesis predicts that there would not be major differences in diet and behavior of dogs who do and dogs who don’t eat poop, and that dogs would mainly eat poop that is fresh—less than two days old. It also predicts that commercial products would not be effective in treating this behavior, nor would behavior modification.
The researchers assure us that commonly held beliefs such as “a gastrointestinal upset, nutritional deficiency or compulsive disorder” had “no clinically established abnormality associated with the behavior.”
Facts About Dogs Who Eat Poop
23% percent of the dogs are stool eaters (eating poop at least one time)
Coprophagia is more common in dogs described as "greedy" eaters
Dogs who eat poop are more likely in multi-dog households
Terriers and hounds were more likely to eat poop than other types of dogs.
Eating stool less than two days old was far more common than consuming older poop.
Dogs who eat poop also enjoy eating dirt and cat stool
75% of coprophagic dogs were more than four years old
Not only do dogs eat poop, but some considered to be coprophagic typically eat it fresh. Through two extensive web-based surveys, the study found that 16% of the dogs sampled were observed eating fresh stool at least six times (this is the group determined to be coprophagic compared to another 7% of dogs which had eaten poop 1-5 times). Of this group, 76% were even more frequent poop nibblers, sampling it more than 10 times. The study found no correlation of coprophagy (poop eating) with age, sex, age of separation from the mother, whether animals were neutered or spayed, type of food eaten, ease of housetraining, or any specific types of behavior such as barking, aggression, destructiveness, anxiety-related behavior or compulsive behaviors.
The dogs did have some things in common, however. They were described as “greedy” eaters (the range of eating styles included “finicky, greedy and normal”), lived in multi-dog households, and would also eat dirt and cat stools. Many were terriers or hounds.
The researchers had four objectives: first, to collect demographic information such as age, breed type, gender and neutering, number of dogs in household, type of food fed, eating behavioral patterns, and so forth. Another survey then directed additional questions to owners of coprophagic dogs, including the ease or difficulty in housetraining, the “age” of the stools that were consumed, and any behavioral modification procedures used to discourage it. Finally, since many products on the market purport to stop coprophagia, they asked about their use and effectiveness.
Surprisingly, coprophagy did not seem to be a “reflection of juvenile behavior”; 75% of the coprophagic dogs were more than four years old. Also, the habit did not seem “to be associated with compulsive-like behaviors.” Although the sample size was too small to make any firm conclusions based on breeds, the analysis did find that hounds and terriers were more likely coprophagic than other dogs.
Interestingly, this study did not reference a previous study from 2010, called “Correlates of Coprophagy in the Domestic Dog (Canis familiaris) as Assessed by Owner Reports” which has information that does not support the findings of the current study. The former study found that neutering males drastically lowers the prevalence of coprophagy (though spaying females had no effect). It also found that dogs with anxiety disorders or oral disorders such as pica and plant-eating were more frequently coprophagic.
So Then, Why Do Some Dogs Eat Their Poop?
As to the why of it all, back to the two proposed hypotheses: one, these dogs are “exhibiting an abnormal behavior stemming from one or more contributing causes,” but none of their findings supported any of those causes. The second, that coprophagy is an adaptive behavioral defense that comes from dogs’ wolf ancestors. It is thought that wolves would consume “fresh feces of injured or sick pack members that might be deposited in the rest areas near the den. If wolves were to remove the feces from rest areas where infective larvae from intestinal parasites would become more numerous over time, consumption is the only method available.”
Now, isn’t that interesting! So wolves ate the poop of pack members to help keep their dens parasite-free. (How wolves would know that poop contained unwelcomed parasites was not explained.) And while the researchers could not find any studies that detailed such behavior with wolves (or other canids), they added, “a comment by noted wolf authority L. David Mech that ‘wolves do commonly practice coprophagy, at least in captivity,’ offers support for this perspective, which was further reinforced by a personal communication with Mech.” If this analysis is correct, then poop-eating dogs might just might be showing off their wolfish roots, a more imaginative and less worrisome explanation than the other options.
The fact that the poop-eating dogs were also found to be “greedy” eaters also lends credence to a Canis lupus antecedent, as the paper noted, “because one would expect greedy eating to be a common wolf characteristic.” (Perhaps that’s why gulping down food was first characterized as “wolfing down” in the 1860s.)
Poop Eating is Normal Dog Behavior
The study ends by reconfirming that coprophagy is not really medically harmful to dogs, although, sadly, some of their humans might find it so disgusting “that the bond with their dog is irreparably damaged.” They also offer a few caveats about the poor showing of the poop-eating-deterrent products, because they cannot attest to how well treatment guidelines were followed. The same can be inferred about behavioral modification techniques, since the researchers did not know how reliably any one method was employed or followed up on.
How to Stop Your Dog From Eating Poop
This study supports the second hypothesis that coprophagy is a natural behavior and not an abnormal one. The research certainly confirms what many guardians already know, which is that limiting access to feces is critical if you don’t want dogs to eat it. In other words, the best way to stop this behavior is by cleaning up all poop in the yard and trying to avoid it when out on walks or in other areas.
- Cleaning. Keep your yard and dog’s living area free of poop
- Training. Get started ASAP on improving your dog's Leave It cue
- Cat Control. Keep kitty litter boxes out of dog's reach
- Supervision. Have a watchful eye when out on walks, be sure to pick up poops immediately
Unfortunately this study found that behavioral management of the feces-eating dogs did little to alter this behavior, with the “leave it” command scoring the highest rate of 4% (which is still really low). But the use of food additives like vitamin and enzyme supplement pills and taste-aversion products marketed for coprophagia scored even more dismally, with only one of the 11 products scoring 2%; three others had a 1% rate, and the rest came in with zero. (They did note that their survey did not explore the degree to which the respondents closely followed directions on the label for those products.) Your best bet might not be to use any commerical products claiming to stop your dog from eating poop and instead focus on training.
A more reliable response to the “leave it” cue would help in these situations, as would using high-value treats to redirect attention and reduce foraging mishaps.