Why Do Dogs Eat Grass?
July 27, 2018
Why dogs eat grass is anybody’s guess. Science is not exactly sure why because there aren’t enough studies probing the issue. But that doesn’t stop the experts from hazarding a guess based on common sense. One thing we do know, most dogs have eaten grass at one point in their lifetimes.
The obvious place to start in answering this question is to go back to a dog’s ancestry and the behavioural habits of wolves. Behavioral scientists have often observed wolves eating grass to relieve some kind of gastrointestinal upset.(1)
However, the study, Why do dogs eat grass?, published in Veterinary Medicine disputes this fact.(2) After studying various groups of dog owners and their dogs’ eating habits, only about 8% of the dogs who ate grass vomited afterwards. While the study couldn’t rule out gastrointestinal distress, it also couldn’t definitively say it was the only reason dogs eat grass. This is called a null hypothesis:
“Plant eating is not particularly related to illness or vomiting,” Benjamin L. Hart, DVM, PhD, DACVB.
Wolves and feral dogs often feed on grass-eating animals too and have been observed eating the belly contents of their prey first before consuming the whole animal. So maybe grass eating is something hardwired into our dogs’ DNA.
Some dogs just like eating grass, particularly young ones. Some dogs eat grass and vomit without ever showing any signs of illness beforehand.
There’s another belief that dogs eat grass because of some dietary deficiency. Another study published in Applied Animal Behavior tested whether diet was an issue.(3) Feeding two different groups of dogs with a standard diet versus one deficient in nutrients, the canines who ate a well-balanced diet enjoyed eating grass even more than the control group:
“Our study found that dogs spent significantly more time eating grass when fed the standard diet and producing normal stools than when they were fed the FOS diet and producing loose stools, suggesting that dogs do not use grass to self-medicate a diarrhoeal gastrointestinal disturbance,” Samantha J. MacKenzie, head researcher.
Not all dogs eat grass to induce vomiting, though it does prove to be an effective treatment for an upset tummy. If you do have a dog with a penchant for eating grass, make sure you know a pesticide-free place where he or she can graze at free will. One good sign that a lawn hasn’t been chemically treated is the presence of weeds. But you still need to watch out for fertilizer use.
Volume 123, Issues 1–2, February 2010, Pages 51-55.
Photo by: Tupfenmonster ~ Barney