Why do dogs eat grass? Science debunks old myths about canine habits

Dogs and humans have shared lives for thousands of years, and most people can recognise basic canine behaviour. Yet some habits—like grass-eating or rolling in mud—still puzzle owners. Recent research has challenged old assumptions, while experts stress the importance of understanding what's normal and what may need attention.

For years, many believed dogs ate grass only to soothe an upset stomach. But studies over the last decade tell a different story. Research by Sueda et al. (2008) and later reviews, including a 2023 meta-analysis in Veterinary Record, found that up to 79% of dogs eat grass without showing signs of illness. The behaviour now links to multiple possible causes: nutritional gaps, boredom, taste, or simple curiosity. No single explanation dominates, leaving the question open.

Growling often alarms owners, but it's a key part of a dog's communication skills. Suppressing it can remove an important warning signal. If a dog growls frequently, though, experts like Dr. Daphne Ketter of Tierverhalten München advise a professional assessment to rule out underlying issues.

Aggression also varies widely. A dog may act differently with strangers than with family, and the owner's relationship with the pet plays a big role in managing risk. Not all aggression signals danger—it's often just communication.

Other odd habits, like rolling in mud or dung, remain unexplained. Theories suggest dogs might mask their scent, scratch an itch, or simply enjoy the sensation. Meanwhile, owners should stay cautious on walks, avoiding pesticide-treated fields or toxic plants, and keep up with regular deworming.

Grass-eating itself isn't usually a problem if occasional. But if a dog gorges on it or seems fixated, it could point to a physical or psychological issue worth checking.

While science has debunked some myths, uncertainties remain about why dogs do certain things. Owners can take practical steps—monitoring grass intake, respecting growls, and avoiding harmful environments. When in doubt, consulting a vet or behaviourist helps distinguish quirky habits from real concerns.