Why Dogs Eat Grass (And the Real Answer Isn't What You Think)
The popular explanation — that dogs eat grass to make themselves vomit when they feel sick — is almost certainly wrong. A study published in Applied Animal Behaviour Science in 2008 surveyed 1,571 dog owners and found that only 9% of grass-eating episodes were preceded by signs of illness, and only 22% of episodes resulted in vomiting at all. Most dogs who eat grass show no signs of illness beforehand and do not vomit afterward. They just eat grass and move on.
So what is actually happening?
The Ancestral Diet Explanation
The most scientifically supported explanation is that grass eating is a behavior inherited from ancestral canines. Wild canids — wolves, foxes, coyotes — eat herbivorous prey whole, including the gut contents. This means plant material has always been part of the canine diet. A dog eating grass may simply be following a deeply instinctual behavior that was adaptive in wild ancestors and has carried forward without clear purpose in domesticated dogs.
Supporting this: a 2009 study published in Veterinary Medicine found that grass eating is significantly more common in young dogs than older ones. The researchers interpreted this as consistent with an innate, exploratory behavior rather than a sickness response — older dogs have learned what they prefer; younger dogs are still sampling their environment.
The Fiber Hypothesis
Some researchers propose that dogs seek out grass when their diet is low in fiber and that they instinctively supplement. A single case study published in the Canadian Veterinary Journal documented a miniature poodle who ate grass compulsively for three years. The behavior stopped completely within days of switching the dog to a high-fiber diet. The author noted that this was one case and should not be generalized, but the fiber angle has some biological plausibility — grass is high in insoluble fiber, which supports digestion.
The Simple Explanation
Some dogs appear to eat grass because they enjoy it. Grass contains nutrients, moisture, and variety that may simply be appealing. Dogs who are otherwise healthy, well-fed, and unstressed engage in occasional grass eating with apparent enthusiasm and no ill effects. The behavior may not require a deeper explanation than that.
When to Pay Attention
Grass eating is generally safe and not a cause for concern on its own. Pay attention when: the behavior suddenly increases dramatically, is followed by consistent vomiting, or the dog appears distressed before eating grass. Those patterns warrant a vet visit. Regular, relaxed grass nibbling during a walk is almost certainly normal.
Sources
- Sueda et al., 2008 — Applied Animal Behaviour Science — 1,571-dog survey finding only 9% of grass-eating episodes preceded by illness signs; 22% followed by vomiting
- Hart et al., 2009 — Veterinary Medicine — survey of 1,371 dogs showing grass eating more frequent in younger dogs, consistent with innate exploratory behavior
- Brown et al., 1977 — Canadian Veterinary Journal — case study of grass eating resolved by high-fiber diet switch in a miniature poodle
- VCA Animal Hospitals — Why Do Dogs Eat Grass? — veterinary clinical overview of grass-eating behavior, safety considerations, and when to consult a vet
For Dog Owners
Browse dog supplies, toys, and accessories in our Dogs collection.
For dog digestive supplements and gut health, search dog digestive supplements on Amazon.
Find unique animal art, shirts, and mugs in our Etsy shop.
From Paw to Tail is a participant in the Amazon Services LLC Associates Program. Links marked with the Amazon tag earn a small commission at no extra cost to you.