FAQ #3: Why does my dog eat grass? – Memphis Area Pet Health and Wellness
This is an age old question fraught with many varied and disparate 
answers. “I have often wondered it myself as I gaze out my kitchen window to watch my my Golden Retriever graze like a tiny, shaggy cow,” writes Dr. Katie Morrill, DVM.
Let’s first address a few possible reasons.
- It’s normal canine behavior! – That’s right. This behavior has been documented in wild wolf populations. It also appears to be a normal instinct for many, but not all, domestic dogs. One theory as to the possible purpose of this behavior involves intestinal worms. The plant material is thought to “scour” the GI tract and help the animal rid themselves of unwanted hitchhikers. This has been observed in dogs, wolves, and also chimps! Most dogs now are on monthly heartworm preventatives that also prevent common GI parasites. (Another reason to give your heartworm prevention EVERY MONTH, people!). If you ever DO see worms in freshly passed stool, though, contact your veterinarian.
- Boredom – Some dogs can show displacement behaviors if they are bored or anxious. Drinking excessive water (in the absence of a medical reason), eating grass, pacing, and many other behaviors can be a way for dogs to expend nervous energy or stimulate themselves. Making sure your dog is getting enough exercise and daily engagement can help curb these types of behaviors. Food puzzles, structured, walks around the neighborhood, and teaching your dog tricks and commands are all ways to do this.
- Pica – This term refers to animals that ingest inappropriate, non-nutritive items and substances. These can range from dirt, to socks, to hair ties, to good old green grass. Sometimes pica behaviors are driven by nutritional deficiencies, especially iron. In my experience, most Labrador’s are born suffering from sock-and-underwear deficiencies that they are desperate to correct – even if it means having those things surgically removed at a later date! However, pica is not considered to be a major cause of grass-eating.
- To Induce Vomiting – This theory is a golden oldie, but not one that probably deserves much credence. Most grass eating does not occur in ill animals, and dogs do not have the cognitive ability to ingest grass in order to consciously induce vomiting or even soothe their stomachs. There may be a shred of this theory attached to the worm-scouring idea, though. If ancient dogs had worms that made them feel sick, the instinctto eat grass to help pass the worms could have been linked to the feelings of sickness. Whether there was any benefit to the vomiting remains to be seen. In one survey of hundreds of owners with grass-grazing canines, most dogs (82-92%) did not regularly vomit after ingesting grass.
So, the take home is that grass eating may serve a purpose, have an underlying cause, or just be a thing some dogs do!
The important thing is to make sure that the grass they’re munching has not been treated with any toxic substances. There are also several non-grass plants that people have in their yards that can cause serious illness if eaten.
For resources on safe vs toxic plants, please see the ASPCA website. If your dog or cat does ingest a toxic plant, contacting the ASPCA poison helpline (for a $65 dollar fee) can give you valuable information.
