By Christine D. Calder,
DVM, DACVB
Board-Certified Veterinary Behaviorist, www.caldervbs.com
Have you ever seen your dog chewing on grass and wondered, “Why is he doing that?” While it may seem strange, eating grass is actually a very common behavior in dogs. Many pet owners worry that it means something is wrong, such as their dogs feeling sick or lacking nutrients. However, research shows that in most cases, grass eating is a normal and harmless behavior.
One possible reason dogs eat grass is boredom. Dogs are intelligent, active animals that need regular mental and physical stimulation. Without enough exercise or attention, they may look for something to do, like munching on grass. This is especially true for dogs who spend a lot of time alone in the yard without toys, companionship, or activities.
Some dogs may simply enjoy the taste or texture of grass. Fresh, tender blades, especially in spring or summer, can be appealing. Just as people enjoy crunchy snacks for the way they feel, dogs may enjoy chewing on grass for the sensory experience.
Grass may also play a role in digestion. It contains natural fiber, which can support healthy bowel movements. In one published case report in the Journal of Veterinary Medical Science(2007), an 11-year-old miniature poodle had been eating grass daily for seven years and often vomited afterward. When the dog’s owner switched to a high-fiber diet, the grass eating, and the vomiting, stopped within just three days. This suggests that some dogs may turn to grass to make up for a fiber deficiency in their diet.
Grass eating may also be an instinctive behavior inherited from wild ancestors. Wolves and other wild canines have been observed eating plants or the stomach contents of herbivorous prey. This behavior likely helped them supplement their diets with roughage and additional nutrients. Even though modern dogs eat complete and balanced meals, some of these natural instincts may still remain.
Another theory is that grass helps eliminate internal parasites. The fibrous texture might assist in physically clearing out the digestive system. While most pet dogs today are protected through regular veterinary care, this ancient behavior could still be part of their behavioral toolkit.
Many people believe dogs eat grass to make themselves vomit when they feel sick. But scientific research suggests this is not very common. In a large study by Dr. Benjamin Hart and colleagues at the University of California, Davis, 1,571 dog owners were surveyed. The results showed that 68% of dogs ate grass on a regular basis, but only 8% showed signs of illness beforehand; around 22% vomited afterward. Interestingly, younger dogs were more likely to eat grass but less likely to appear sick or vomit. These findings suggest that most dogs are not eating grass because they feel unwell.
Another study from the University of New England looked at the link between grass eating and hunger. Twelve healthy dogs were observed over six days and offered kikuyu and couch grass three times per day. The dogs were more likely to eat grass before meals and less likely to eat it later in the day, suggesting that hunger may play a role. The study also found that the dogs showed no clear preference for one type of grass over the other.
So, when should you be concerned? Most of the time, grass eating is completely normal and nothing to worry about. However, you should speak with your veterinarian if your dog is eating large amounts of grass frequently, vomits often after eating grass, shows signs of tiredness or loss of appetite, or suddenly starts eating more grass than usual. Also, always make sure the grass your dog has access to is not treated with pesticides, herbicides, or other chemicals that could be harmful if ingested.
If you want to reduce or manage your dog’s grass-eating habits, there are several simple steps you can take. First, talk to your veterinarian to make sure your dog is getting enough fiber in his diet. Increasing daily exercise and providing more mental stimulation, such as interactive toys, puzzle feeders, and training games, can also help. Teaching your dog alternative behaviors such as “come,” “look,” or “look at that (voluntary eye contact)” can be helpful for redirecting attention away from grass. Supervising your dog while outdoors, especially in unfamiliar areas, is also a good idea.
In the end, grass eating is a common and usually harmless behavior in dogs. It can be caused by boredom, hunger, dietary needs, or natural instincts. Most importantly, studies show that it is rarely a sign of illness. As long as your dog is healthy and has access to safe, untreated grass, there is usually no reason for concern. And if you are ever unsure, your veterinarian is the best person to help guide you.