Why dogs eat grass—and other puzzling behaviors explained by science

Dogs often behave in ways that puzzle their owners, from rolling in strong smells to munching on grass. While some actions may seem odd, experts say many are perfectly normal. Recent research has even shed new light on why dogs eat grass, moving beyond old assumptions about digestion or nausea. For years, people believed dogs ate grass to settle their stomachs or induce vomiting. But studies over the last decade tell a different story. Research published in Journal of Veterinary Behavior (2019) and Animals (2022) suggests dogs may self-medicate for parasites or seek missing nutrients. A 2021 meta-analysis by Bjone et al. found that 70–80% of dogs eat grass regularly without showing signs of illness. Scientists now link the habit to evolutionary foraging instincts or a need for dietary fibre. Other behaviours, like growling or barking loudly, also serve clear purposes. Growling is a key form of communication and should never be discouraged. Loud barking, meanwhile, can signal fear rather than aggression. Aggression itself is often misunderstood—it's a way for dogs to express themselves, not always a sign of danger. Dogs may also act differently around different people, depending on their relationship and past experiences. Some show strong hunting instincts, which owners must manage carefully. Rolling in strong odours might help them hide their scent or share information with other dogs. Even eating small amounts of grass is usually harmless, though sudden or excessive grazing warrants a vet visit. Regular deworming remains important, as parasites can cause health problems if dogs ingest contaminated grass. Any abrupt change in behaviour—whether eating habits, vocalisation, or body language—should prompt a check-up. Understanding dog behaviour has come a long way in recent years. What once seemed strange now often has a clear explanation, backed by science. Owners can help their pets stay healthy by observing habits, seeking vet advice when needed, and respecting natural instincts—whether it's a growl, a roll in the mud, or a nibble of grass.