Why Does My Dog Eat Grass and Poop? (Pica and Coprophagia Explained)

You feed them premium, freeze-dried, organic kibble. You buy them gourmet treats. And yet, you watch in horror as your dog happily grazes on grass like a Holstein cow, or worse, snacks on… well, poop.

Why do they do it? Is something wrong with them? Are they missing nutrients? Or are they just gross?

These behaviors—eating non-food items (Pica) and eating feces (Coprophagia)—are two of the most common complaints veterinarians hear. They are repulsive to us, but in the dog world, they often have logical, biological, or behavioral explanations.

Here is the deep dive into why your dog treats the world like an all-you-can-eat buffet, and how to stop it.

Mystery 1: Why Do Dogs Eat Grass?

A commonly held belief is that dogs eat grass to make themselves vomit when they feel sick. The Truth: Studies show that fewer than 25% of dogs vomit after eating grass, and only 10% show signs of illness beforehand. Most dogs graze happily and keep it down.

The Real Reasons for Grazing:

1. They Like the Taste: Fresh spring grass is full of sugar and moisture. It has a satisfying crunch. To many dogs, it is simply a salad bar.
2. Fiber Deficiency: Some studies suggest dogs crave roughage to help digestion.
3. Boredom: “I am in the yard. Nothing is happening. I guess I will mow the lawn.”
4. Ancestral Instinct: Wolves eat the stomach contents of their prey, which usually consists of fermented grass, berries, and plants.

Should you stop it? Generally, no. Unless the grass has been treated with chemical fertilizers, pesticides, or herbicides (which are toxic and cause cancer), grazing is a harmless, natural behavior.

Mystery 2: Why Do Dogs Eat Poop? (Coprophagia)

This one is harder to stomach. Watching your dog eat their own stool (autocoprophagia) or another dog’s stool (allocoprophagia) is baffling. But biology offers some clues.

1. The “Mother” Instinct

Mother dogs instinctively eat their puppies’ poop to keep the den clean and hide the scent from predators. It is a hard-wired survival mechanism.

• The Habit: Some puppies mimic their mother. If not corrected, this “cleaning” habit can persist into adulthood.

2. Nutritional Deficiency (Malabsorption)

If a dog isn’t digesting their food properly, their poop essentially comes out looking (and smelling) just like it went in. To a dog, it still smells like food because it is partially undigested food.

• Medical Red Flags: If an adult dog suddenly starts eating poop, see a vet. It could be Exocrine Pancreatic Insufficiency (EPI) (where the pancreas fails to produce enzymes), Parasites (worms stealing nutrients), or Thyroid issues causing voracious hunger.

3. The “Forbidden Snack” (Cat Poop)

To a dog, the litter box is a vending machine of “Almond Rocas.”

• Why: Cat food is much higher in protein and fat than dog food. Therefore, cat poop is high in protein and fat. It is a high-value treat.
• The Fix: This is rarely behavioral; it’s opportunity. Put the litter box behind a baby gate or on a raised surface.

4. Attention Seeking

You are in the yard. You are ignoring the dog. The dog eats poop. You run over screaming “NOOO!”

• The Lesson: “Wow! When I eat this, Mom plays chase with me!” Even negative attention is attention.

How to Stop Coprophagia

1. The Management Strategy (Immediate Cleanup)

This is the only 100% cure. If there is no poop in the yard, they cannot eat it.

• Pick up immediately after they go. Do not leave it for “later.”
• On walks, keep their head up and reward them for looking at you.

2. Dietary Deterrents

You can add things to their food that makes the poop taste bad (worse?).

• Pineapple / Zucchini: Contains enzymes that reportedly change the taste of the stool.
• Commercial Chews: Products like Coprophagia deterrents (usually containing MSG, chamomile, or parsley) aim to make the stool bitter.
• Meat Tenderizer: Sprinkling unseasoned meat tenderizer on food is an old breeder trick.

3. Training “Leave It”

This is a life-saving command.

• The Game: Put a low-value treat on the floor. Cover it with your hand. Say “Leave It.” Wait for them to stop sniffing your hand. The moment they back away, click and give them a high-value treat from your other hand.
• The Goal: “Leave It” means “Ignore that thing on the ground, and you will get something better from me.”

4. The Basket Muzzle

If your dog is obsessed and scavenges on walks (eating poop, dead animals, or trash), a Basket Muzzle (like a Baskerville) is a humane management tool. It allows them to pant, drink, and take treats, but the grid prevents them from picking up waste. It protects them from parasites like Giardia and worms.

When It’s Pica (Eating Rocks, Socks, Metal)

Eating poop is gross. Eating socks is deadly. Pica is the compulsion to eat non-food items.

• The Danger: Intestinal blockage. A sock cannot pass through the gut. It requires emergency surgery.
• The Cause: Often anxiety, OCD, or severe gastrointestinal disease (IBD).
• Action: If your dog eats objects, this is beyond “training.” You need a veterinary behaviorist and strict management (crating/muzzling) to keep them alive.

Summary

• Grass: Fine, as long as it’s chemical-free.
• Poop: Gross, but usually behavioral. Clean the yard faster.
• Rocks/Socks: Medical emergency. See a vet.

You aren’t a bad owner because your dog eats poop. You just have a dog with very primitive, scavenger instincts. Clean up, train “Leave It,” and maybe skip the kisses for a few minutes after they come inside.