As you may have noticed from your trips to the park, some dogs relish eating grass as though it were a gourmet treat. Others, however, don't seem overly interested, and may only take an occasional little munch every now and then. Like many dog owners, you've probably wondered about this behavior. The definitive answer to the question "Why do dogs eat grass?" has not been found. But experts have some interesting theories.
Natural-born scavengers. According to this theory, modern-day domesticated dogs eat grass because, in their evolutionary past, they were scavengers—wild animals that ate whatever they could find when they needed nutrition. Sometimes that included grass.
Dogs are omnivores. As omnivores—animals that eat both meat and vegetation—dogs may simply have a natural craving for grass. Some dogs may eat more grass than others because the taste appeals to them more.
Stomach cleansing. If your dog is fond of grass, you may have noticed that eating grass makes him vomit. The correlation between eating grass and vomiting is well documented, but experts still aren't entirely clear if dogs eat grass because they feel a need to cleanse their stomachs, or if they vomit because the grass has given them an upset stomach. If it's the former, then eating grass may be a natural and instinctive way for dogs to purge the contents of their digestive tract. The mystery, however, gets deeper when you consider that some dogs eat grass without any consequences.
When you should be concerned
If your dog has an appetite for an occasional grass snack, this may be perfectly normal behavior. And if it makes him vomit now and then, there may still be no need for alarm. However, if he vomits more than once or twice, or if your non-grass-eating dog suddenly starts eating great quantities of grass, you should have him checked by your vet. This may be an indication that something is wrong with his digestive system.
The use of pesticides, herbicides, fertilizers, and other lawn treatments is another cause for concern. If your dog is a grass eater by nature, make sure he isn't able to snack on any lawn that's been treated. When in doubt, play it safe and keep him away from questionable patches of grass in the neighborhood or the park.