Why Dogs Eating Excrement: The Science Behind Coprophagia
Why are dogs eating excrement? Explore the evolutionary, physiological, and behavioral science behind canine coprophagia, plus practical solutions that work.
Quick Answer: Why Are Dogs Eating Excrement?
Dogs eating excrement (coprophagia) is a common, evolutionarily rooted behavior affecting an estimated 16-25% of dogs. Research published in Veterinary Medicine and Science (2018) found that coprophagia is most strongly linked to an innate scavenging drive inherited from wolves — not nutritional deficiency, as many owners assume. Puppies frequently outgrow the behavior by 9-12 months, but adult-onset coprophagia can signal underlying medical conditions including exocrine pancreatic insufficiency (EPI), intestinal malabsorption, or parasite loads. If your dog suddenly begins eating feces after never doing so before, schedule a veterinary exam to rule out disease.
It's one of the most viscerally unpleasant things a dog owner can witness: your dog cheerfully consuming feces — their own, another dog's, or even cat litter box deposits. The behavior has a clinical name — coprophagia — and while it makes us gag, the science behind why dogs do it is genuinely fascinating.
Rather than treating coprophagia as a mysterious "bad habit," modern canine science offers a clearer picture. The behavior sits at the intersection of evolutionary biology, digestive physiology, and learned reinforcement. Understanding these mechanisms is the first step toward managing it effectively.
The Evolutionary Basis: What Wolves Taught Modern Dogs
🐺 Ancestral Context
Wolves and wild canids regularly practice coprophagia, particularly in the context of den hygiene and pup-rearing. Mother wolves consume the feces of their nursing pups during the first 3-4 weeks of life to keep the den clean and reduce scent signatures that could attract predators. This maternal coprophagia is nearly universal among wild canids and is hormonally driven.
Additionally, wild canids are opportunistic scavengers. The feces of herbivores like rabbits and deer contain partially digested plant matter — essentially a second-pass extraction of nutrients. For a wolf in lean winter months, consuming herbivore droppings represents a caloric opportunity, not a pathology.
A landmark 2018 study by Dr. Benjamin Hart and colleagues at the UC Davis School of Veterinary Medicine, published in Veterinary Medicine and Science, surveyed over 1,500 dog owners and found compelling evidence that coprophagia in domestic dogs is an inherited scavenging trait rather than a sign of dietary deficiency or psychological disturbance.
Key findings from the Hart study:
- 16% of dogs were classified as "frequent" stool eaters (observed consuming feces 6 or more times)
- 77% of coprophagic dogs preferred feces less than 2 days old
- 85% preferred the feces of other dogs over their own
- Dogs described as "greedy eaters" (those who eat food rapidly) were significantly more likely to be coprophagic
- Breed categories labeled as "shy" or "bold" by the AKC showed no significant difference in coprophagia rates
The researchers concluded that coprophagia reflects a hardwired scavenging disposition — dogs who are highly food-motivated simply extend their "eat everything edible" strategy to include feces. This is consistent with the broader understanding that domestic dogs evolved as village scavengers, not pure predators. As noted by the Merck Veterinary Manual, scavenging is one of the most fundamental canine survival strategies.
The Physiological Mechanism: How the Canine Body Processes This Behavior
The Physiology of Coprophagia
Dogs have a shorter gastrointestinal tract relative to body size compared to humans, with a transit time of approximately 8-10 hours (compared to 24-72 hours in humans). This rapid digestion means that feces can still contain recognizable undigested proteins, fats, and carbohydrates — particularly if the originating dog consumed a calorie-dense commercial diet.
From a canine olfactory perspective, feces carry a rich chemical signature. The dog's 300 million olfactory receptors (compared to our 6 million) detect volatile fatty acids, bile salts, and bacterial metabolites in feces that signal "food content." To a dog's nose, fresh feces doesn't smell the way it smells to us — it smells like partially processed nutrients.
Several physiological conditions can amplify coprophagic behavior by altering the composition of feces or the dog's nutrient-absorption capacity:
| Condition | Mechanism | Prevalence |
|---|---|---|
| Exocrine Pancreatic Insufficiency (EPI) | Pancreas fails to produce digestive enzymes; food passes through largely undigested, making feces nutrient-rich and attractive | Most common in German Shepherds; estimated 1 in 1,000 in predisposed breeds |
| Intestinal Parasites | Roundworms, hookworms, and giardia compete for nutrients, creating a perceived caloric deficit that drives scavenging | ~30% of shelter dogs carry at least one intestinal parasite (CDC estimates) |
| Diabetes Mellitus | Glucose malabsorption leads to polyphagia (excessive hunger); dog seeks calories from any available source | Affects ~1 in 300 dogs; higher in older, overweight females |
| Cushing's Disease (Hyperadrenocorticism) | Excess cortisol increases appetite dramatically; coprophagia emerges as part of generalized polyphagia | ~1-2 in 1,000 dogs annually; breeds at risk include Poodles, Dachshunds, Boxers |
| Thyroid Disease (Hypothyroidism) | Metabolic slowdown can alter gut motility and appetite regulation | Affects roughly 0.2-0.8% of the dog population |
For dogs with these underlying conditions, the feces they consume may genuinely contain higher caloric value than normal, and the dog's body is essentially signaling a nutrient deficit. This is why sudden-onset coprophagia in an adult dog who previously showed no interest warrants a veterinary workup including a complete blood count (CBC), serum chemistry panel, fecal float, and potentially a trypsin-like immunoreactivity (TLI) test for EPI. Expect to spend $200-$450 on this diagnostic panel at a general practice clinic.
Is Dogs Eating Excrement Normal? Debunking Common Myths
| Common Myth | What Science Actually Shows |
|---|---|
| "My dog eats poop because their food lacks nutrients." | The 2018 Hart study found no correlation between diet type (commercial, raw, homemade) and coprophagia rates. Dogs on AAFCO-complete diets were equally likely to eat feces as those on varied diets. |
| "Adding meat tenderizer or pineapple to food will stop it." | These home remedies (papain and bromelain enzymes) aim to make feces taste unpleasant. The Hart study found commercial coprophagia deterrents were effective in only ~2% of cases. Taste aversion is not the primary driver. |
| "Only sick or neglected dogs eat feces." | The UC Davis research found coprophagic dogs were rated by owners as happier and more outgoing than non-coprophagic dogs. The behavior correlates with enthusiasm for food, not distress. |
| "My dog eats poop to get back at me." | Dogs lack the cognitive capacity for spite or revenge. Coprophagia is driven by scavenging instinct and reinforcement history, not emotional retaliation. |
| "Puppies will always grow out of it." | While many puppies stop by 9-12 months, the Hart study found that dogs who continue past age 1 are likely to continue lifelong unless behavior is actively managed. |
Breed Variations and Behavioral Patterns
While the UC Davis study found that breed alone was not a strong predictor of coprophagia, certain behavioral tendencies associated with breed groups do show correlations:
- Terriers and Hounds: Bred for independent foraging and scavenging; higher food-drive scores correlate with increased coprophagia rates
- Retrievers (Labrador, Golden): Bred for "soft mouth" carrying and oral fixation; Labs in particular are notorious for indiscriminate eating (pica), which extends to feces consumption
- Herding breeds (Border Collies, Australian Shepherds): May engage in coprophagia as a displacement behavior when understimulated; environmental enrichment often reduces the behavior
- Brachycephalic breeds (Shih Tzus, Pugs): No significant breed-linked increase, but small size means owners are more likely to notice and report the behavior indoors
Multi-dog households show higher coprophagia rates than single-dog homes, likely because the presence of fresh feces from housemates provides more opportunity. Cat-owning dog households face an additional challenge: cat feces are particularly attractive to dogs due to the high protein content of feline diets and the concentrated odor of cat waste. This is sometimes colloquially called "toilet bowl syndrome" when dogs raid litter boxes.
When Coprophagia Signals a Medical Problem
⚠️ When to See Your Veterinarian
Consult your veterinarian promptly if your dog's coprophagia is accompanied by any of the following:
- Sudden onset in an adult dog (over 2 years old) with no prior history
- Weight loss despite normal or increased food intake
- Chronic diarrhea or loose, greasy, pale stools (steatorrhea)
- Vomiting after consuming feces
- Increased thirst and urination (polydipsia/polyuria)
- Dull coat, flaky skin, or other signs of nutrient malabsorption
- Visible worms or rice-grain-like segments (tapeworm proglottids) in feces
These symptoms suggest an underlying metabolic or parasitic condition that requires diagnostic testing and treatment, not just behavioral management.
One particularly concerning risk: dogs who consume the feces of livestock (horses, cattle) or wildlife may ingest ivermectin residues from deworming medications. Ivermectin toxicity in dogs — particularly in MDR1 gene mutation carriers (Collies, Australian Shepherds, Shetland Sheepdogs) — can cause blindness, seizures, coma, and death. If your dog has access to pastureland or farm environments, discuss MDR1 testing with your vet (approximately $65-$85 via the Washington State University Veterinary Clinical Pharmacology Lab).
Practical Takeaways: Managing Coprophagia in Daily Life
Evidence-Based Management Strategies
Since coprophagia deterrents show only ~2% efficacy, the most effective approach combines environmental management with positive reinforcement training:
- Immediate feces removal: Pick up all feces within 5 minutes of elimination. The Hart study found dogs overwhelmingly prefer feces less than 2 days old — removing it promptly eliminates the primary opportunity. Use biodegradable waste bags (e.g., Earth Rated, ~$14 for 270 bags).
- Teach a reliable "Leave It" cue: Using force-free, positive reinforcement methods, train your dog to orient toward you instead of toward feces on walks. Start with low-value items (dry kibble on the floor), reward heavily with high-value treats (freeze-dried liver, ~$12/3oz bag), and gradually proof the behavior near feces. Expect 4-8 weeks of consistent daily practice for reliable performance.
- Leash management on walks: Use a 4-6 foot leash in areas where other dogs defecate. Avoid retractable leashes in high-risk zones — they give the dog too much range to snatch feces before you can react.
- Cat litter box solutions: Place litter boxes behind baby gates with cat-sized openings, use top-entry litter boxes (e.g., Modkat, ~$50), or invest in a self-cleaning litter box (Litter-Robot 4, ~$699) that removes waste within minutes.
- Increase dietary enrichment: Food-motivated dogs who practice coprophagia often benefit from slower feeding methods that satisfy their oral foraging drive. Puzzle feeders (Kong Classic, ~$15; Outward Hound Nina Ottosson puzzles, ~$15-$30) redirect the "mouth everything" impulse toward appropriate outlets.
- Supplement considerations: While commercial deterrents have poor efficacy, some veterinary behaviorists recommend adding 1-2 teaspoons of canned pumpkin (plain, not pie filling) per 10 lb of body weight to meals. The fiber alters fecal texture and palatability. This is safe and inexpensive (~$2/can) but not universally effective.
How Is This Different From Humans?
The human reaction to coprophagia is one of intense disgust — an evolved pathogen-avoidance mechanism. Humans have a highly developed behavioral immune system that triggers nausea and revulsion at potential disease vectors, including feces. This is adaptive for us because our longer digestive transit times and different gut microbiome make us more vulnerable to fecal-oral pathogens.
Dogs, however, have a fundamentally different relationship with their gastrointestinal environment:
- Stomach acidity: A dog's gastric pH ranges from 1-2 (highly acidic), compared to human gastric pH of 1.5-3.5. This stronger acidity provides a more robust chemical barrier against ingested bacteria.
- Gut microbiome resilience: Canine gut flora is adapted to scavenging, including a higher proportion of Fusobacteria and Clostridia species that can process decomposing organic matter.
- Shorter transit time: Pathogens have less time to establish in the canine GI tract before being expelled.
- No psychological disgust response: Dogs lack the cognitive framework for disgust as humans experience it. Feces is evaluated as "edible" or "not edible" based on scent and prior reinforcement, not emotional aversion.
This doesn't mean coprophagia is risk-free for dogs. Consumption of feces from diseased animals can transmit parvovirus, giardia, coccidia, and roundworms. Dogs who practice coprophagia should be kept on a rigorous parasite prevention protocol — your veterinarian can recommend an appropriate monthly dewormer and vaccination schedule.
Related Behaviors: What Else Falls Under the Scavenging Umbrella?
Coprophagia rarely exists in isolation. Dogs who eat feces frequently display other scavenging-adjacent behaviors that share the same underlying food-motivation circuitry:
- Pica: Consumption of non-food items (rocks, socks, mulch). More dangerous than coprophagia due to intestinal blockage risk. Dogs who eat feces AND non-food items should be evaluated for compulsive disorder.
- Counter-surfing and trash raiding: Same scavenging drive applied to human food sources. Management strategies overlap heavily with coprophagia prevention.
- Grass eating: Extremely common (observed in ~68% of dogs); generally benign unless accompanied by vomiting. May serve a roughage or gut-motility function.
- Rolling in feces or carrion: An olfactory camouflage behavior inherited from wolves. The dog rubs strong-smelling substances into their coat, possibly to mask their scent from prey. Related to, but distinct from, coprophagia.
Frequently Asked Questions
Is it dangerous for my dog to eat their own feces?
Consuming their own feces carries relatively low risk if your dog is healthy, parasite-free, and on a complete diet. The primary concerns are transmission of parasites from other animals' feces, ingestion of medication residues, and the unpleasantness of the behavior itself. A healthy dog eating their own fresh stool is unlikely to become ill, but the behavior should still be managed to prevent escalation.
Can puppies get sick from eating feces?
Yes. Puppies have immature immune systems and are particularly vulnerable to parvovirus, which can survive in feces for months in the environment. A puppy who consumes feces in a public area (dog park, sidewalk) where an infected dog has defecated is at genuine risk. Ensure your puppy completes their full DHPP vaccination series (typically at 6-8, 10-12, and 14-16 weeks) before allowing access to high-traffic areas.
Will adding certain foods to my dog's diet make their feces unappealing?
The evidence is weak. Commercial deterrent products (e.g., NaturVet Coprophagia Deterrent, ~$12 for 50 chews; For-Bid, ~$18 for 120 packets) contain ingredients like monosodium glutamate, yucca schidigera, or dl-methionine intended to alter fecal taste. The UC Davis study found these products effective in only about 2% of cases. Some owners report success with adding meat tenderizer (papain enzyme) or pineapple (bromelain), but no controlled study supports their efficacy. A more reliable approach is environmental management and training.
Why does my dog eat cat feces specifically?
Cat food is typically higher in protein (30-40% crude protein) than dog food (20-30%), and cats' shorter digestive tracts mean more undigested protein passes into their feces. To a dog's nose, cat feces smells strongly of protein and fat — essentially, it smells like food. This is why coprophagia directed at cat litter boxes is one of the most persistent forms of the behavior and requires physical barriers (baby gates, top-entry boxes) rather than taste deterrents.
Should I punish my dog for eating feces?
No. Punishment-based approaches (yelling, nose rubbing, shock collars) are counterproductive for coprophagia for several reasons. First, the behavior is intrinsically self-reinforcing — the dog finds feces rewarding, so punishment must be severe enough to override that reward, which creates fear and anxiety. Second, punishment often teaches the dog to eat feces faster or only when unobserved. Positive reinforcement of an incompatible behavior ("Leave It" followed by a high-value treat) is more effective and avoids welfare concerns. The American Kennel Club recommends force-free redirect-and-reward methods as the standard approach.
How long does it take to stop coprophagia with training?
For dogs who began the behavior as puppies and have no underlying medical cause, consistent environmental management (immediate cleanup) combined with "Leave It" training typically shows significant reduction within 4-8 weeks. However, complete elimination of the behavior may take 3-6 months, and some dogs with strong scavenging drives may require lifelong management. Relapse is common if cleanup routines lapse or if the dog encounters an unsupervised feces opportunity during the training period.
References
- Hart, B.L., et al. (2018). "The paradox of eating feces: An investigation of coprophagia in dogs." Veterinary Medicine and Science, 4(2), 105-113. Full text via PMC/NIH
- Merck Veterinary Manual: Undesirable Behaviors in Dogs
- American Kennel Club: How to Stop Your Dog From Eating Poop
This article is for educational purposes and does not replace professional veterinary advice. If your dog exhibits sudden-onset coprophagia or any accompanying symptoms described above, consult your veterinarian for a thorough examination and diagnostic workup.
Tom Renshaw
All our authors care for dogs every day — read more of their work on the authors page.
