Fri Jun 2

Why does my dog eat grass? And when is it not safe for them?

Written by: Susan Hazel, Associate Professor, School of Animal and Veterinary Science, University of Adelaide

Have you ever wondered why your dog is eating your beautifully cropped lawn or nibbling at the grass at the dog park?

Eating grass is a common behaviour in pet dogs. Some surveys show up to 80%^[1] of guardians notice their dog regularly snacking on the grass.

Grass eating isn’t a new behaviour either, or only done by our new designer dog breeds. Studies in Yellowstone National Park show plant matter (mostly grass) is found in up to 74% of wolf scats ^[2], suggesting the behaviour is possibly inherited from the beginning of doggy time.

The answer to why your dog eats grass may simply be: because they like to. Shutterstock

So why does my dog eat the grass?

A lot of people think dogs eat grass when they have a sore stomach, believing grass causes dogs to vomit. This is probably not the case; a study with 12 dogs that ate grass daily ^[4] found there were few vomiting episodes and the ones that did occur came after the dog had eaten a meal.

And if a dog has a mild gastrointestinal disturbance because of something they’ve been fed, they are in fact less likely ^[5] to eat grass than if they are fed a normal diet.

Other theories include that dogs eat grass because they want a laxative or that it provides roughage in their diet (get that fibre!).

Like the vomiting discussed above, there is little to no scientific proof for most of these theories. For example, in the study of 12 dogs mentioned above ^[6], all of them were wormed and had no previous digestive problems. Yet all 12 still happily ate grass (709 times).

Their main finding was that when the dog had not yet had their daily meal, they were more likely to eat grass. In short, the hungrier the dog, the more likely they were to eat some grass.

The answer to why your dog eats grass may simply be: because they like to. Your dog may be bored, and chewing on grass is something to do.

Maybe your dog just enjoys eating grass. Ripping grass from the ground can be satisfying. The texture and taste of grass offers something different to what they usually eat. You may even notice they prefer grass in certain seasons; perhaps fresh spring grass a favourite delicacy.

You may even notice your dog prefers grass in certain seasons. Shutterstock

Is there any reason why you shouldn’t let your dog eat grass?

Well, yes, there are several. Firstly, you may not want your dog eating your neighbour’s immaculately presented fancy Kikuyu lawn.

More importantly, though, grass is sometimes treated with herbicides. Grass at the local oval or parkland may have been treated or sprayed. Some local councils use a non-hazardous dye to show where grass has been sprayed with herbicide ^[7], which is very helpful.

Lawn chemicals are frequently detected in lawn for up to 48 hours after they’re applied, and have also been detected in the urine of dogs with access to grass ^[8] treated this way.

Research has suggested there may be a link ^[9] between bladder cancer in dogs and exposure to herbicides.

In fact, dogs may even act as sentinels; the same chemical exposures appear in the urine of dogs and people sharing the same environment ^[10].

There are some circumstances in which it’s better for your dog not to eat the grass. Shutterstock

If you are using herbicides on your own grass, remove your dog, their toys, food and water bowls from the area prior to any application.

Make sure the pesticide has completely dried out before you allow the dog back in the area, and be certain to check the packaging for the appropriate drying time period.

This is particularly the case for granular pesticides or fertilisers that soak into the soil, as these can require up to 24 hours or longer.

If you want to reduce the risk even further, hand weeding may be a better option ^[11].

Apart from grass, many leaves, flowers and berries from common plants can be toxic to your dog. This includes ^[12] plants such as oleander and arum lily; even oregano and bay leaves can cause vomiting and diarrhoea in dogs.

One of the best things you can do for your dog is take them for a walk. And if they eat some grass along the way, provided it has not been sprayed with herbicide, you have nothing to worry about.

Don’t worry if they occasionally vomit. If there is more serious vomiting or diarrhoea, however, please consult your vet.