Who can blame a dog for grazing in the backyard or snatching a mouthful on a walk? To many dogs, grass is a tasty treat. 

Years ago, when I asked a veterinarian—who was also my boss—why dogs eat grass, he looked at me and said, “Because it tastes good.”

Like many people, I used to think dogs only ate grass when they had an upset stomach. After all, studies show about 25% of dogs vomit after eating grass. But only about 10% showed signs of illness beforehand. That suggests grass-eating is less about nausea and more about instinct or behavior.

Historically, dogs’ ancestors ate entire prey animals after a hunt. Along with flesh, bones and organs, they also consumed stomach contents, including grass and plants. That likely provided the roughage they needed. 

These days, most dogs are not scavenging carcasses in the yard. Still, some dogs seem determined to add those fibrous snippets of green to their diets. It seems modern dogs cannot live on kibble alone.

Besides instinct, dogs may eat grass out of boredom, anxiety, curiosity or a desire for attention. When dogs are understimulated, they often find their own ways to stay occupied, including grazing on the verdant lawn. 

For an anxious dog, chewing grass may be a little like a person biting their nails. Puppies, meanwhile, explore the world with their mouths, and a patch of grass can be just another thing to investigate.

But not all grass is salad and solace. Letting dogs graze freely in unfamiliar areas can come with risks. Lawns are often treated with pesticides and fertilizers, and not everyone posts warning flags. Ingesting these chemicals can be toxic. Signs of poisoning may include excessive drooling, vomiting, diarrhea and abdominal pain. In more serious cases, tremors, seizures and collapse can occur. Contact your veterinarian right away if your dog shows any of these symptoms.

Grass or soil contaminated with infected feces can expose dogs to roundworms, hookworms, giardia and other parasites—some of which can also spread to humans. If your dog spends time in high-traffic pet areas such as parks or trails, ask your veterinarian about an appropriate parasite prevention plan.

This year, we’re replacing our patchy lawn with artificial turf. It’s hard to say how our dog Oakley will handle losing his favorite snack bar. I suspect he’ll peer through the fence, wondering whether the grass really is greener—and tastier—on the other side.