In this article

1. How many dogs eat poo?
2. The missing-nutrient idea, put to the test
3. So why do dogs do it?
4. Is eating poo bad for your dog?
5. What helps: fewer chances, better choices
6. When to talk to your vet

You look up from your phone in the park and your dog is chewing something with great concentration. Then the smell reaches you. It is a habit that upsets plenty of owners, and one explanation comes up again and again: that eating poo is a sign of a dietary deficiency¹.

Large surveys of the habit point elsewhere. Here is what they found, why powders and tablets rarely help, how to limit the chances, and when to ask your vet.

How many dogs eat poo?

Much of what is known comes from two online surveys by Benjamin Hart's team at the University of California, Davis, published in 2018: 1,552 replies comparing dogs that eat poo with dogs that do not, and 1,475 from owners of regular poo eaters².

About nine in ten replies came from the United States, and owners chose to take part, so treat the figures as a guide rather than a census². A Dutch study suggests the habit may be more common still: 261 of 564 owners questioned had seen their dogs eat poo⁴.

Hart counted only dog poo, and many dogs cast the net wider. In a small Italian study, 18 of 23 poo eaters ate other animals' droppings, most often a cat's, a coypu's or a horse's⁵.

The missing-nutrient idea, put to the test

Hart's team turned the nutrient explanation into a prediction. If eating poo made up for something missing, poo eaters should be fed a markedly different diet. They were not: kibble was the main food for 82.3% of frequent poo eaters and 78.3% of dogs never seen eating poo². It is a coarse comparison, by type of food, but the researchers found no evidence relating the habit to diet².

A smaller study from the University of São Paulo questioned the owners of 30 poo eaters and 40 dogs that did not eat poo, and found no difference in the number of meals, the dogs' nutritional background or the commercial food they ate⁶. The Royal Kennel Club thinks the habit is too common for a deficiency to explain most cases¹, and the PDSA's vet-written guide says it is very rarely due to a medical problem or something lacking in the diet³.

To a scavenger, then, poo can be food, and dogs may smell undigested fats and proteins in it¹. That is a long way from a dog on a complete diet hunting for a missing nutrient.

You may have heard	What the research found
Something is missing from their food	No link with diet in Hart's surveys, or in a smaller one that asked about meals and food2, 6
It's a puppy habit	Many puppies grow out of it3, but frequent poo eaters were no younger than other dogs2
They don't find poo disgusting	Poo eaters were as easy to house-train as other dogs2
It's a compulsive disorder	Compulsive-like behaviours were no more common in poo eaters2

So why do dogs do it?

Hart's surveys add two clues. Poo eaters were far more likely to be described as greedy eaters, 51% against 28% of dogs never seen eating poo, and more likely to live in a home with two or more dogs². And they were fussy about one thing: freshness. In both surveys, 82 to 85% of regular poo eaters went for poo no more than two days old².

From that, Hart offers an idea rooted in wolves. A sick or injured wolf may leave droppings near the den, and the eggs of the worms most often found in wolf droppings need at least two days before they can infect. Eating fresh droppings, the only way a wolf can remove them, would clear them while the risk was still low².

Dogs, on this view, inherited a version of that tidy-up, which would explain the taste for fresh poo and why poo eaters house-train as easily as other dogs². It is a neat fit, but no study has watched wild wolves clearing droppings from their resting places, and the authors call the idea tentative².

A mother dog eating her puppies' poo, which keeps the nest clean¹, is completely normal³. Puppies sometimes eat their own or their littermates' poo out of curiosity, and this usually stops with age³.

Day to day, the PDSA lists habit, hunger, boredom, stress or anxiety, and attention: a very bored dog may decide that being told off beats being ignored³. Hunger can follow too little food, more exercise, or an illness or medicine that raises appetite³. In the São Paulo survey, living with another poo eater stood out⁶.

Is eating poo bad for your dog?

The PDSA says poo eating does not often cause health problems for dogs³. In the small Italian study, 23 healthy poo eaters showed no measurable difference in the gut bacteria tested from 21 dogs never seen doing it, and were no more likely to carry the disease-causing bacteria and viruses screened for. Parasites were not tested⁵.

It is still worth discouraging, because poo can carry parasites, viruses and bacteria, and horse manure can hold worming medicines that may be toxic to dogs¹. Keep your dog's worming up to date and ask your vet for the latest advice¹.

Poo eating can also muddle a poo test. Researchers at Utrecht University tested dogs' poo monthly for a year. When a sample showed roundworm eggs, the dog was kept away from poo for three days and retested: 120 of 246 roundworm-positive samples, 49%, came back clear, and the researchers counted the first result as a false positive from poo eating⁴. If your vet asks for a sample, mention the habit.

For your own sake, do not let a poo eater lick you, and wash your hands well after touching their mouth or saliva¹.

What helps: fewer chances, better choices

Owners of regular poo eaters in Hart's second survey had rarely stopped the habit: chasing a dog away from poo worked for 1 to 2%, rewarding a 'leave it' for 4%, and the 11 food additives and tablets sold to stop it for 0 to 2%². The survey took in only dogs seen eating poo at least weekly, there have been no proper trials, and owners may not have followed the instructions². Aim to give your dog fewer chances, and make coming to you more rewarding than the poo.

Advice on muzzles differs. The Royal Kennel Club suggests a basket muzzle on walks, which still lets your dog pant¹. The PDSA advises against one, because it does not stop a dog wanting the poo and they will often still try³.

If a young puppy eats poo overnight, the PDSA suggests a last toilet trip as late as possible, a spot to go away from their bed and an early start; most pups grow out of it³.

When to talk to your vet

Most poo eating comes down to habit, hunger, boredom or stress³. Some conditions make it more likely, though: medicines such as steroids, illnesses that increase appetite such as diabetes, thyroid problems or worms, trouble digesting food, dementia, and illnesses that change the smell or texture of poo¹. If your dog only ever eats one particular dog's poo, the PDSA suggests having that dog checked as well³.

Speak to your vet if your dog suddenly starts eating poo, or eats it regularly¹. A check-up for medical causes comes first; once your dog has the all-clear, a certified behaviourist can help with training³.

Poo eating is one of the less lovely parts of life with a dog, but it is rarely a sign that anything is missing from their bowl. Keep a bag in every pocket and make coming away worth their while.

Sources and further reading7 sources

The small numbers in the article link to the source behind each fact. Sources open on their own websites.

1. Why does my dog eat poop?The Royal Kennel Club
2. The paradox of canine conspecific coprophagyVeterinary Medicine and Science (Wiley)
3. Why do dogs eat poo?PDSA
4. Coprophagy in dogs interferes in the diagnosis of parasitic infections by faecal examinationVeterinary Parasitology (Elsevier)
5. Coprophagy in Healthy Dogs Does Not Alter Fecal Core Microbiota or Increase Carriage of EnteropathogensAnimals (MDPI)
6. Canine coprophagic behavior is influenced by coprophagic cohabitantJournal of Veterinary Behavior (Elsevier)
7. Anthropogenic Food Subsidy to a Commensal Carnivore: The Value and Supply of Human Faeces in the Diet of Free-Ranging DogsAnimals (MDPI)