Pondering the mysteries of our universe:

“Doc, why does my dog eat grass?”  Most treasured readers, I don’t think a day goes by in my never-ending quest to make this world a better place for our beloved dogs and cats that I’m not asked this question.  I remember myself as a snotty-nosed inquisitive veterinary student, asking my animal behavior professor this very question.  Her answer then—just as the answer would be today—was:  “We (veterinary researchers) have a lot of theories as to why dogs eat grass, but the bottom line is that we still can’t say for sure!”

Attempting to give a definite answer to this question that would be correct in every case, is still a risky proposition because (like everything else in the medical professions) there are no easy, consistent, or absolutely provable answers.  To give some idea of the length and breath of the data that’s out there regarding this not-so-simple question, when I sat down this morning to write this humble article, just for fun I typed in the words “why dogs eat grass” into Google’s search engine.  It returned 2,060,000 possible websites!!! Wow!!!

The first answer most people usually give to this question is that dogs eat grass when they have a stomach ache in order to make themselves vomit. My response to this explanation is: “Do dogs eat grass to make themselves vomit, or, do they vomit because they’re eating grass?”  This cause and effect relationship of dogs eating grass is an important question to ask, because first of all, no one can prove that dogs or cats are intelligent enough to use grass as a medicinal herb.  Who would have ever taught them such a thing?  Secondly, if indeed they’re eating grass in order to make themselves vomit, then how do we explain the fact that most dogs whose owners tell me their dogs eat grass, say their pets never vomit at all?

Another possible answer to this question is that dogs have a instinctual craving for either the minerals that might be in grass, or the actual roughage and bulk that is found in the plant fibers themselves.  There may be some truth to this answer.  In the wild, the present-day ancestors of our modern dog breeds (wolves, coyotes, the dingo, and foxes) eat mostly small, grass-eating, rodents:  mice, rats, rabbits, etc.  When these dogs consume their prey, they will usually consume as well the grass in the stomach of whatever critter they’ve just killed.  Therefore, it is thought that since dogs have evolved over the millennia to be able to tolerate this grassy stomach contents of their prey as part of their regular diet, that there is something in their physiology that is satisfied whenever our pet dogs eat grass.  This possible answer is all well and good, except that there are a lot of dogs out there in this world whose owners tell me never eat grass.

Another reason people say dogs eat grass is that they are predicting that it’s going to rain.  The main trouble with this reasoning, is that as a kid, I heard an old farmer’s saying that went something like this:  “If you see your dog (or cat) eat grass today, it’s time to hook up the horses and mow the hay.”  (For those non-farmers out there who read this article, what this saying means is that because grass hay needs two or three days for it to dry before it can be baled, a dog eating grass meant there would be three days of clear weather ahead.)  As quaint as it may sound, I think we can ignore this eating grass and weather prediction theory.

The same is true regarding whether or not a dog or cat has intestinal worms.  There are pets who eat grass and have worms, and there are pets who eat grass who don’t have worms.

There are also some other bizarre reasons out there that people give for why dogs eat grass.  One of my favorites (and one of the hardest to disprove) is the fact that in the Garden of Eden, when Adam and Eve and all of the animal kingdom lived in perfect harmony, and no one ate each other for lunch, every living creature were vegetarians.  Therefore, this compulsion in our pets to consume grass is the sign of a longing for the time of our distant primordial innocence when we all just got along with one another, and there was none of this present day (please excuse the pun) dog eat dog stuff.  I kinda like this reason a lot.

Some researchers say that when a dog is eating grass, they’re actually sniffing and tasting whether or not another dog has invaded their territory. Others say that since the meat of herbivores (grass-eating animals like cows, goats, and sheep) make up several of the primary ingredients found in a dog or cat’s diet, that the taste of grass may be reminiscent of what they just had for dinner.

I can hear it out there now: “And so Doc, just what is the reason you feel that dogs or cats eat grass?”  Well, I think the answer my treasured readers is one that was given to me by a young man named Nicholas.  Nic and his dad brought one of their pets in to my clinic to see me and, as it frequently happens, his dad asked why their dog was eating grass all the time.  As always, I went through my list of reasons as I just did above (I usually leave out the Garden of Eden explanation, mostly because I don’t want to seem too much like a nut) and as is always the case, I left the poor father more baffled then he was before he asked.

After a couple of seconds of awkward silence, suddenly young Nic, who I think will some day be President of these United States, raised his hand and asked,  “Dr. Orzeck, do you think the reason most dogs eat grass is simply because they like the way it tastes?”

It took a couple of more seconds before the profoundness of this simple answer sunk in to my frazzled brain.  And I guess that’s the answer that I like best.  For the same reason I like pepperoni pizza, blue cheese dressing on my salad, and the occasional Buffalo chicken wing, I think is the same reason our pets like to eat grass:  They just like the way it tastes!!!

Thanks again.

Doctor Oz

Copyright © 2007 by Richard Orzeck, DVM
The information in this article is based upon the author’s personal experience and his best interpretation of veterinary data at the time of writing. It is not intended to render veterinary advice or service. Specific needs and questions concerning your pet’s health should always be addressed by his or her best friend, your local veterinarian.


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