Why Dogs Eat Poop

New research on an old question
By Karen B. London PhD, January 2018

What? Eat Poop? Me?

On top of most lists of undesirable behavior in our dogs is coprophagy, which is eating poop. Most commonly, the poop that dogs are eating is their own or that of other dogs, and most humans find this revolting.

In a paper called “The paradox of canine conspecific coprophagy” researchers used survey data to learn more about this behavior. (“Conspecific” means “same species” so the title refers to dogs eating dog poop.) The paradox referred to in the title is that dogs eat feces and yet they “typically show an aversion to conspecific feces.” When I first read this, I had to wonder what dogs the researchers were talking about, because many of the dogs I know are drawn to poop and sniff it with great interest. It turns out that the aversion the authors speak of refers to dogs generally eliminating outdoors and avoiding doing so where they live and sleep such as in the house and especially in crates.

This paper had four goals: 1) To find out basic data about coprophagy such as how common it is and which dogs do it, considering age, gender, diet, breed and number of dogs in the household. 2) To look at the association between ease of housetraining and coprophagy, which the authors consider a measure of aversion to feces. 3) To determine the age of stool that is eaten. 4) To evaluate the success of various types of behavioral modification and of a number of commercial products that are marketed for the prevention of stool eating.

The researchers proposed two competing hypotheses 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.

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.

Approximately 16 percent of the dogs were stool eaters, which was defined as having eaten stool at least six times. (Another 7% of dogs had eaten poop 1-5 times.) The study found no correlation of coprophagy 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. Dogs who also ate cat poop and dirt were more likely to be coprophagic, and so were dogs who lived in a household with at least one other dog. Attempts to stop the behavior were generally successful 0-2% of the time, whether the guardians tried commercial products or behavior modification. Success rates were as high as 4% when people told dogs to “leave it alone!”

Some correlations with coprophagy were found in the study. Dogs who were described as “greedy eaters” were more likely to be coprophagic. 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.

This study supports the second hypothesis that coprophagy is a natural behavior and not an abnormal one. However, it is possible that as-yet undiscovered correlates of the behavior may contradict this finding. 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.

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.

Have you had any luck ending the poop eating of a dog prone to coprophagy?

Karen B. London, PhD, is a Certified Applied Animal Behaviorist and Certified Professional Dog Trainer who specializes in working with dogs with serious behavioral problems, including aggression. She is the author of five books on canine training and behavior.

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