If your dog occasionally munches on grass, you're not alone — it's one of the most common behaviors reported by dog owners worldwide. But why do they do it?
1. It's Instinctive and Normal
A 2008 study published in Applied Animal Behaviour Science surveyed 1,571 dog owners and found that 68% of dogs ate grass on a daily or weekly basis. Only 8% of dogs showed signs of illness before eating grass, and only 22% vomited afterward. The researchers concluded that grass eating is a normal behavior inherited from wild ancestors, not primarily a sign of illness.
2. Dietary Fiber
Some veterinarians suggest that dogs eat grass to supplement fiber in their diet. A frequently cited case report describes a miniature poodle that ate grass daily for seven years and stopped completely after being switched to a high-fiber diet. While this is anecdotal, it suggests that some grass eating may be driven by a nutritional need.
3. Ancestral Behavior
Wild canids (wolves, coyotes, foxes) regularly consume plant material. Studies of wolf scat have found grass and other vegetation in 2–10% of samples. Grass eating may be an evolved behavior that helps purge intestinal parasites — the fiber can increase intestinal motility and wrap around worms, facilitating their expulsion. This is supported by research on wild chimpanzees who swallow rough leaves for the same purpose.
4. They Like the Taste
Sometimes the simplest explanation is the best one. Many dogs seem to enjoy eating fresh spring grass, particularly young shoots. Dogs are not obligate carnivores — they're omnivores with a long evolutionary history of eating varied diets that include plant matter.
When to Worry
Occasional grass eating is generally harmless. However, consult your vet if your dog is eating grass frantically and vomiting frequently, showing signs of gastrointestinal distress, eating grass treated with pesticides or herbicides, or suddenly increasing their grass consumption. The ASPCA recommends ensuring any grass your dog has access to is free of chemical treatments.