The strange reasons your dog eat grass (and poop)

Don’t pretend like your pup hasn’t done it.

By Thomas Ling

Published: Friday, 12 May 2023 at 12:00 am

Dogs. Love them all you want, but it won’t stop them wolfing down all manner of mud, slugs, stones, non-existent homework – and yes – poop. But have you ever wondered why they eat some of the things they do? For instance, exactly why do dogs eat grass?

Glad you asked: this canine conundrum has several intriguing answers. Well, theories at least. Although the neuroscience of dogs is a growing field of study, scientists still can’t tell the exact motivation behind this puzzling behaviour.

“The little research that has looked into this question hasn’t been conclusive,” explains Dr Emily Blackwell, lecturer in companion animal behaviour and welfare at the University of Bristol. “There could be a variety of plausible reasons for canine grazing – and there may be no one correct answer but several.”

So, with that said, what are the working explanations to why dogs eat grass? We’ve fetched everything you need to know below.

Why do dogs eat grass?

Firstly, it’s thought that eating grass could be a sign of anxiety and conflict in dogs, possibly as they’re suppressing the urge to carry out another action.

“It may be a displacement behaviour – something that happens when an animal has conflicting motivations,” explains Blackwell. “It’s like when we’re sitting in the dentist’s waiting room. We may really want to run away, so we do something else like biting our nails to relieve the anxiety.”

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However, in many dogs, eating grass may be a way of hounding you for affection.

“If owners react to this behaviour, then dogs quickly learn that’s a good way of getting attention,” says Blackwell.

“True, it’s not one of the most common attention-seeking behaviours, but it can develop for that reason. And if they don’t get a response from you, they may simply be grazing because they’ve not got a lot else to do.”

But what if your dog is feasting on the front lawn when you’re not around? Surely, that’s not a howl for attention, right? Indeed, it might ­– just might – be because your pooch is trying to supplement their diet.

“Some have theorised dogs exhibit this behaviour to increase the fibre they eat,” says Blackwell. “However, this is only a theory. It hasn’t been tested whether dogs low in fibre and more likely to eat grass.”

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What about the most worrying possibility: is your pup guzzling grass as they have upset stomach? Again, potentially. After all, it’s theorised wolves also consume grass to help purge their intestines of parasites.

However, it’s unlikely that grass causes your dog to be sick. One 2008 study found that while 68 per cent of dogs regularly eat grass, only 22 per cent of them are sick afterwards. Overall, that’s pretty good odds you won’t have to clean doggy vomit off your lawn.

And if they are sick? Well, just be thankful they didn’t eat something even grosser…

Why do dogs eat poop?

We’re all friends here: it’s fine to admit you’ve seen your dog eating poop – their own or another animal’s.

Fortunately, according to Blackwell, it’s unlikely to harm your pup, unless the faeces belonged to an animal carrying a serious illness.

Unfortunately, however, just like grass, it’s not exactly clear why your dog would be tempted to tuck into a turd. But canine behavioural experts think doo-doo dining could stem from the animal’s curiosity at a young age.

“Puppies are naturally exploratory – and they’ll taste anything,” says Blackwell “And faeces don’t taste or smell gross to them in the way they might do for us.”

But even if they’re not sold on the taste, you might inadvertently encourage your dog to feed on faeces when trying to prevent that very behaviour.

“Normally, the consequences of this behaviour are that owners rush over to any faeces during walks, trying to get there first to stop their dog. But this signals to the dog that faeces are important to the owner, increasing its value. And that could make dogs ever more determined to reach it before their owner” says Blackwell.

“In this way, a lot of dogs are actually eating poo because they’ve almost been trained to by their owner! It’s all about how you respond.”

Bottom line: if you see an unguarded number two during walkies in the park, your number one response shouldn’t be to rush over to it. Especially if you don’t have a dog (it’ll look really weird).

About Dr Emily Blackwell

Dr Emily Blackwell is a Lecturer in animal behaviour and welfare at the University of Bristol. Much of her research focuses on why our animals behave the way they do – and how to improve their lives.

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