Why do dogs eat grass and poop? Pet experts explain this weird behavior

Any dog owner with a backyard knows the agony of stepping outside to find Fido has torn up the lawn — again. There’s food aplenty in the kibble bowl, so why would dogs nosh on things like grass? While you might write it off as just one more weird dog behavior, experts say that your dog’s grass-chomping habits may have complex evolutionary roots.

Inverse spoke with pet experts to answer all your burning questions about why dogs ingest strange items and whether it’s safe for them to eat grass.

Why do dogs eat grass?

“Grass eating is observed in both domestic and wild canines, yet the reason for it remains largely unknown,” Katy Nelson, a senior veterinarian at Chewy, tells Inverse.

However, pet experts do have numerous theories on why your dog might be chowing down on greenery.

One theory posits that eating grass helps ease gastrointestinal issues and can induce vomiting if the dogs have an upset stomach.

“In my personal experience, I see dogs eating grass commonly when they don't feel well or have gastrointestinal upset,” Kelly Hicks, a medical oncology resident veterinarian at Oregon State University, tells Inverse.

“The thought is that grass helps potentially with digestion and passage of stools.”

But not every expert agrees. Katherine Pankratz, a board-certified veterinary behaviorist, tells Inverse dogs rarely vomit after they eat grass, so dogs are unlikely to be eating the stuff to soothe an upset tummy.

Danielle Bernal, a veterinarian with Wellness Natural Pet Food, tells Inverse dogs may consume grass to add fiber to their diet. This theory has a fair bit of scientific support. Pankratz cites a 2007 study: A poodle that was eating grass (and vomiting in this case, though this is less common) stopped after it switched to a commercial high-fiber diet.

“Although there is some evidence that dogs can digest carbohydrates, it may be most likely that the supplement of dietary fiber was likely the benefit and not the grass itself,” Pankratz explains.

Some research suggests that grass eating is an evolutionary behavior descended from dogs’ ancient ancestors: wolves. “It is thought that eating grass is an innate behavior, one that was present in domestic dogs’ distant ancestors,” Jamie Freyer, a veterinarian at Veterinarians.org, tells Inverse.

Your canine might also simply be bored or ravenous. According to a 2007 study, researchers found a correlation between dogs eating grass and the time of day. Dogs were more likely to eat grass before a meal — when hunger was highest — compared to after a meal.

It’s also possible the answer might be simpler than we think.

“There isn’t one specific reason that your pup likes the occasional grass snack. They just like the taste, texture, and feel of eating grass,” Freyer says.

Are dogs really carnivores?

You may be surprised to learn that dogs are not, in fact, true carnivores.

“Actually, in contrast to the cat, who is an obligate carnivore, dogs are omnivorous,” Freyer says.

Unlike cats, dogs can get important acids and vitamins from vegetable oils, according to Nelson. And Pankratz adds that canine molars have “relatively flat surfaces” that can grind bones and plants.

“Dogs can also digest almost 100 percent of the carbohydrates they consume and have a larger small intestine as compared to that of a strict carnivore,” Nelson says. The small intestine is where most of the nutrient absorption from food occurs.

In fact, dogs may actually need non-meat food sources from time to time such as grain to maintain a healthy diet.

“There is a link between grain-free diets in dogs [and] heart disease (i.e. cardiomyopathy), which supports the statement that dogs cannot be purely carnivorous animals,” Hicks explains.

Though it’s fair to say that grass is not an appropriate alternative source of food. If your dog consumes grass, it may pass it “fully intact,” Bernal says. “Unlike true herbivores, dogs are not designed to break down the hard, fibrous structure of a blade of grass and turn it into energy like a cow, sheep, or horse would.”

What other weird substances will dogs eat?

Much to their owners’ dismay, dogs are tempted to eat pretty much anything under the Sun — including inedible non-food items.

“Since dogs are scavengers at heart, they will sniff for remnants of food whenever available in pursuit of a tasty reward,” Bernal says.

“Their tendency to explore the world with their mouths often leads to eating things that most of us would not consider food,” Freyer says.

Some common non-food items that dogs have been known to eat include feces (their own or another animal’s), tree bark, toilet paper, dirt, and rocks.

If this sounds like the behavior of your dog, don’t panic. Most of the time it is fairly normal behavior. Consumption of seemingly strange items isn’t always a sign of poor pet training, experts say.

“Some dogs are more likely to use their mouths to explore their environments, such as puppies and young dogs, and dogs have a normal need to chew,” Pankratz says.

In fact, Bernal adds, “the reason dogs may eat these odd substances is the same reason they may eat grass.”

Veterinarians refer to the compulsive canine practice of eating non-food items as “pica.” However, if your canine companion is eating non-food items more often than not, it might be time to bring them in for a check up. “A variety of medical issues could contribute to this behavior of pica, such as nutritional deficiencies, inflammatory bowel disease, and parasites,” Nelson says.

There could also be mental health concerns that would explain this behavior.

“Other behaviors like attention-seeking, separation anxiety, and boredom can lead to pets eating or chewing on things they ordinarily would not have,” Nelson adds.

Whatever the reason, if your dog has a habit of eating foreign objects, you want to keep them under direct supervision whenever possible to prevent medical issues.

And, there is one item on that list you might want to watch out for. Eating poop — a practice known as “coprophagia” — is one of the more common and perturbing non-food items that dogs consume, and this one can have consequences. Poop contains a multitude of bacteria and other microbes and some of these species, when ingested, can cause an infection.

Further, you might want to watch out for objects that might be weirdly shaped, and as such, might not pass as easily. “[These objects] can pose an issue later down the line if [an] object is unable to be digested and gets lodged somewhere in the gastrointestinal tract, causing an intestinal obstruction,” Hicks says.

Is it safe for dogs to eat grass?

“For the most part, eating grass and similar plant-like materials is ok for your dog,” Freyer says.

Bernal adds, “Typically, eating grass is not harmful for a dog’s health unless it is occurring all the time.”

Nelson agrees though she says you still need to keep a close eye on your dog’s grass-eating and make sure they’re not consuming it in bulk.

“Grass itself is not toxic to dogs, but consuming excess quantities could lead to signs of illness such as vomiting, discomfort, and increased frequency of defecation,” Nelson says.

Nelson adds that if your lawn has recently been treated with fertilizers or pesticides, you’ll want to keep the dog off the grass for at least 48 hours. If your pet is ingesting grass at the dog park, keep an eye out for signs indicating the lawn may have been treated with chemicals.

However, if your dog is exhibiting any unusual behavior: vomiting, suddenly eating grass for the first time or increasing the amount of grass it consumes, consult a veterinarian. The grass may contain parasites that could be harmful to your pet, and the parasites may be spurning your dog to consume more grass, Pankratz says. In instances like these, she might consider a parasite preventative medication.

Pankratz stresses there is no “one-size-fits-all" to keep your pet from eating undesirable items. You can start by identifying the underlying reason why your dog is eating grass or another item, which may require help from a veterinarian.

If your dog is simply bored, find other appropriate outlets to meet its needs, such as dog-safe chew toys or food if the animal is indeed hungry. You can also consider taking your dog out for a walk after meals, Pankratz says.

Hicks recommends you remove any potential ingestible objects when the dog is left unsupervised. It may also be necessary to crate your dog while you’re gone to prevent them from getting into areas of the house where they can eat foreign objects. Pankratz also suggests avoiding grassy areas on walks and keeping your dog leashed at all times. It might even be appropriate to have the dog wear a muzzle in certain environments, Pankratz says.

But the task is a difficult one.

“I think it can be hard to train dogs not to eat things they aren't supposed to ingest,” Hicks says.

Freyer also suggests using simple commands such as “leave it” to direct your dog to stop eating the item or applying a substance to make the object “taste bitter and nasty enough that the dog should leave it alone.” Products that are safe to use can often be purchased at pet stores, but consult your veterinarian first.

Pankratz says you can also consider behavioral modification — a form of guided training that teaches the dog to think differently about and appropriately deal with tempting behaviors. For example, if your dog shows an interest in eating grass, calmly interrupt (without threat or fear) with a diversion, and then guide your dog on what they should do instead with the skills that they know (i.e., sit and look at you, touch their nose to your hand) or a more acceptable behavior (i.e., chase a ball) and reward them for doing so.

Why do dogs raid the trash for food?

If you’ve ever seen your dog pilfering through the trash, again: Don’t blame yourself. It does not necessarily mean a sign of poor training. It could simply be a callback to your pup’s learned evolutionary behaviors, or, more simply, a means to pass the time.

“Dogs are scavengers and, evolutionarily, their scavenging behaviors brought them to living alongside human civilization,” Pankratz explains.

Freyer adds, “When they raid the trash, it is likely because something in there smells tasty and they want to eat it.” Dogs possess an incredible sense of smell. In fact, their noses contain 300 million olfactory receptors. That’s 50 times that of humans, who have a meager six million. As such, the scent of leftover food may literally be too strong to resist.

“So while we may not smell that bit of steak that we dropped in the trash after dinner last night, your dog certainly can,” Nelson says.

Importantly, though, it is necessary to keep them away from the trash can, as eating leftover foodstuffs could give them a bellyache or worse, pancreatitis, Freyer says. They also run the risk of ingesting a foreign body that they can’t pass.

“In most cases... dogs recognize that knocking down the garbage bin daily is not acceptable household behavior, so if your dog is showing that they cannot resist, implementing additional training is highly recommended for their safety,” Bernal explains.

There are other strategies you can use, too. For example, you can keep your trash cans behind closed doors and closets, or purchase specialized tightly sealed rubbish bins that keep all the smells inside and away from your dog’s sensitive nose.

So yes, dogs eat weird things like grass and garbage. Often, there’s no need to intervene. But now you know the reasons why, and when it’s necessary to interject — or call your vet for backup.