Why Do Dogs Eat Grass? Veterinarian Explains the Science

Last Updated on March 6, 2025 by Dogs Vets

You’re enjoying a peaceful morning in the backyard when suddenly your dog starts munching on grass like it’s a gourmet salad. If you’ve ever wondered, “Why on earth is my dog eating grass?” you’re not alone. This peculiar behavior confuses many pet parents and sparks concerns about whether it indicates a health problem or nutritional deficiency.

As a veterinarian with over 15 years of experience in companion animal medicine, I can assure you that grass-eating is one of the most common canine behaviors I discuss with worried pet owners. The good news? In most cases, this behavior is completely normal. But understanding the science behind why dogs eat grass can help you determine when it’s harmless and when it might warrant a closer look.

The Evolutionary Origins of Grass-Eating

To understand why your domesticated companion chews on your lawn, we need to look back at their wild ancestors. Dogs evolved from wolves, who are primarily carnivores but occasionally consume plant material. Studies of wolf scat have revealed that wild canids do ingest vegetation, including grass, in small amounts.

This evolutionary history has left our domestic dogs with certain instinctual behaviors. While your pampered pooch may not need to hunt for their dinner, many primitive behaviors remain hardwired in their DNA – and grass-eating appears to be one of them.

Common Reasons Dogs Eat Grass

Research in veterinary science has identified several potential explanations for grass-eating behavior. Here are the most well-supported theories:

1. Natural Scavenging Behavior

Dogs are facultative carnivores, which means they primarily eat meat but can survive on plant matter when necessary. Unlike obligate carnivores (like cats), dogs have evolved some ability to digest and extract nutrients from plant materials.

Dr. Benjamin Hart, a distinguished professor at the UC Davis School of Veterinary Medicine, conducted one of the most comprehensive studies on grass-eating in dogs. His research suggests that this behavior is a normal scavenging tendency inherited from wild canid ancestors who would occasionally consume entire prey animals – stomach contents and all – which often contained plant material.

2. Dietary Fiber Supplementation

One common theory is that dogs eat grass to increase fiber in their diet. Plant material provides fiber that can help regulate digestion, and some veterinary nutritionists believe dogs may instinctively seek out grass when they need additional roughage.

Fiber aids in proper intestinal function by:

• Promoting regular bowel movements
• Supporting beneficial gut bacteria
• Helping regulate stool consistency
• Assisting with the sensation of fullness

If your dog seems particularly eager to eat grass after switching foods or when experiencing mild digestive upset, they might be seeking additional fiber to help their system run smoothly.

3. Self-Induced Vomiting

Perhaps the most widely discussed theory – and one that has gained significant scientific support – is that dogs sometimes eat grass to induce vomiting when they feel nauseous or have stomach discomfort.

In Dr. Hart’s study, only about 25% of dogs routinely vomited after eating grass, suggesting this isn’t the primary motivation for all grass-eating dogs. However, for some canines, particularly those who rapidly ingest large amounts of grass without much chewing, it does appear to serve as a natural emetic (vomiting inducer).

The long, unchewed blades can tickle the throat and stomach lining, triggering the vomiting reflex. Some experts believe this represents a form of self-medication – when dogs feel unwell, they may instinctively eat grass to purge whatever is causing their discomfort.

4. Psychological Factors

For some dogs, grass-eating may have psychological components:

Boredom relief: Dogs with insufficient mental and physical stimulation may eat grass simply as something to do. This behavior is more common in younger dogs and high-energy breeds who need regular exercise and enrichment.

Attention-seeking: Some clever canines learn that eating grass gets a reaction from their owners. If you rush over and engage with your dog whenever they start munching on grass, they may repeat the behavior to gain your attention.

Anxiety or stress: Just as humans might bite nails when anxious, some dogs engage in repetitive behaviors like grass-eating when feeling stressed or anxious. In these cases, the behavior may become compulsive.

5. Nutritional Exploration

Puppies and young dogs often explore their environment through their mouths. Grass-eating may begin as simple curiosity about a new taste or texture and develop into a habit over time. Young dogs are naturally more experimental with what they put in their mouths.

The Science of Taste: Why Dogs Choose Grass

Interestingly, dogs appear to be somewhat selective about the grass they eat. Research indicates they may prefer younger, more tender shoots that contain higher moisture content and potentially more digestible nutrients.

Dogs have fewer taste receptors than humans – about 1,700 compared to our 9,000 – but they can still distinguish between different flavors. Their taste buds are particularly attuned to detect:

• Sweetness (which may explain preference for certain grasses)
• Sourness
• Bitterness
• Saltiness
• Umami (savory flavors)

The slightly sweet flavor of new spring grass may be particularly appealing to dogs, which explains why many pet owners notice increased grass consumption during spring and early summer when fresh growth is abundant.

When Grass-Eating May Indicate Health Issues

While grass-eating is usually normal behavior, certain patterns might suggest an underlying problem:

Sudden Increase in Grass Consumption

If your previously uninterested dog suddenly becomes obsessed with eating grass, this change could indicate digestive discomfort or another health issue. Conditions that might cause increased grass-eating include:

• Gastric inflammation or irritation
• Inflammatory bowel disease
• Gastroesophageal reflux
• Intestinal parasites
• Pancreatitis

Excessive Grass Eating Combined With Other Symptoms

Pay particular attention if grass-eating is accompanied by:

• Decreased appetite
• Weight loss
• Lethargy
• Diarrhea
• Increased thirst or urination
• Bloody stool
• Persistent vomiting (beyond occasional post-grass episodes)

These combinations of symptoms warrant veterinary attention, as they could indicate more serious digestive disorders or other health problems.

Compulsive Grass-Eating

When grass-eating becomes an obsessive behavior that your dog cannot easily be distracted from, it may indicate underlying anxiety or compulsive disorder. Some dogs with psychological issues develop fixations on eating non-food items (a condition called pica), and grass can become a target of this compulsive behavior.

Is Eating Grass Dangerous for Dogs?

For most dogs, occasional grass consumption poses minimal health risks. However, there are several important safety considerations:

Toxic Chemicals and Pesticides

The greatest danger comes not from the grass itself but from chemicals that may have been applied to it. Lawn treatments can include:

• Herbicides
• Pesticides
• Fertilizers
• Fungicides

Many of these substances are toxic to dogs, especially when freshly applied. Always keep dogs away from recently treated lawns and be cautious about allowing your dog to eat grass in public parks or unfamiliar areas where you don’t know the treatment history.

Toxic Plants

Dogs don’t always distinguish between safe grass and potentially harmful ornamental plants. Some common garden plants that are toxic to dogs include:

• Lilies
• Azaleas
• Daffodils
• Tulips
• Foxglove
• Sago palms

If your dog is a known grass-eater, ensure your garden doesn’t contain toxic plants they might consume alongside the grass.

Intestinal Parasites

Unclean outdoor environments may harbor parasites in the soil and grass, including:

• Roundworms
• Hookworms
• Whipworms
• Giardia

Regular parasite prevention is essential for dogs who frequently consume grass or spend time outdoors.

How Veterinarians Evaluate Grass-Eating Behavior

When concerned pet owners bring up grass-eating during veterinary visits, we evaluate several factors:

1. Frequency and intensity: Occasional nibbling differs from obsessive consumption
2. Behavioral context: Is the behavior triggered by specific situations?
3. Physical examination: Checking for signs of digestive issues
4. Medical history: Previous GI problems or dietary changes
5. Diet evaluation: Is the current food meeting nutritional needs?

Based on this assessment, a veterinarian may recommend:

• Dietary adjustments (potentially higher fiber food)
• Behavioral modifications
• Environmental enrichment
• In some cases, diagnostic tests to rule out medical causes

Practical Management Strategies for Grass-Eating Dogs

If your dog’s grass-eating habit concerns you, here are veterinarian-recommended strategies:

Safe Grass Alternatives

Provide dog-safe plants that satisfy the urge to graze:

• Cat grass kits: Despite the name, these wheat, oat, or barley grass kits are safe for dogs and can be grown indoors
• Wheatgrass: High in chlorophyll and fiber, many health-conscious dog owners offer small amounts
• Dog-safe herbs: Basil, rosemary, and parsley in small amounts can provide interesting flavors and textures

Dietary Adjustments

Work with your veterinarian to optimize your dog’s diet:

• Consider high-quality dog foods with appropriate fiber content
• Some veterinary nutritionists recommend adding small amounts of steamed vegetables
• Ensure proper hydration, as inadequate water intake can contribute to digestive discomfort

Environmental Enrichment

Boredom-related grass-eating often responds well to:

• Interactive toys that require problem-solving
• Regular exercise appropriate for age and breed
• Training sessions that provide mental stimulation
• Scheduled playdates with other dogs
• Rotating toys to maintain novelty and interest

Creating a Safe Outdoor Environment

If you can’t prevent grass-eating entirely:

• Maintain a section of your yard that remains untreated with chemicals
• Consider testing soil for contaminants if you live in an area with industrial history
• Monitor which plants are growing in areas your dog has access to
• Create designated digging or exploration areas with dog-safe landscaping

When to Call Your Veterinarian

While most grass-eating is benign, certain situations warrant professional attention:

• Grass-eating accompanied by repeated vomiting or diarrhea lasting more than 24 hours
• Significant increase in grass consumption without obvious explanation
• Ingestion of potentially toxic plants alongside grass
• Signs of intestinal blockage (repeated unsuccessful attempts to vomit, abdominal pain, lethargy)
• Blood in vomit or stool following grass consumption

Your veterinarian can help distinguish between normal behavioral grass-eating and symptoms requiring medical intervention.

Conclusion: Understanding Your Grass-Eating Dog

The science behind why dogs eat grass reveals that this peculiar behavior typically represents normal canine instinct rather than cause for alarm. From evolutionary adaptations to practical self-medication, grass-eating serves various purposes in the canine behavioral repertoire.

By understanding these underlying motivations, you can better assess when your dog’s lawn-munching habit is harmless and when it might signal a need for veterinary care. For most dogs, the occasional grass snack is simply part of being a dog – a remnant of their wild heritage expressed in the safety of your backyard.

As both a veterinarian and a dog owner, I’ve learned that many so-called “strange” dog behaviors actually make perfect sense when viewed through the lens of canine evolution and physiology. So the next time you catch your furry friend grazing in the yard, you’ll have a deeper understanding of this fascinating behavior that connects our domestic companions to their wild ancestors.

Frequently Asked Questions

Q: Should I stop my dog from eating grass?

A: In most cases, occasional grass-eating doesn’t require intervention. However, you should prevent access to chemically treated grass and monitor for excessive consumption or concerning symptoms. If the behavior seems compulsive or is accompanied by other symptoms, consult your veterinarian.

Q: Does eating grass mean my dog has a nutritional deficiency?

A: Scientific research has not established a clear link between nutritional deficiencies and grass-eating behavior. Most dogs on complete and balanced commercial diets eat grass despite having their nutritional needs met. However, discussing your dog’s diet with your veterinarian is always worthwhile if you have concerns.

Q: Why does my dog eat grass but never vomit?

A: While vomiting is commonly associated with grass-eating, research shows only about 25% of grass-eating dogs regularly vomit afterward. Many dogs appear to enjoy the taste or texture of grass and digest it without issue. Self-induced vomiting is just one of several possible motivations for grass consumption.

Q: Is certain grass better or safer for dogs to eat?

A: Untreated, pesticide-free grass is safest. Young grass shoots may be more digestible and less likely to cause irritation. Some dog owners grow special pet grass (often wheat, oat, or barley grass) indoors for safer consumption. Always ensure your dog doesn’t have access to chemically treated lawns.

Q: Can eating grass cause intestinal blockages in dogs?

A: Intestinal blockages from grass are rare in dogs but not impossible, particularly in small breeds who consume large amounts. The greater concern is the potential consumption of toxic chemicals on treated grass or the ingestion of dangerous plants alongside the grass. If your dog shows signs of abdominal pain, repeated unsuccessful attempts to vomit, or lethargy after eating grass, contact your veterinarian immediately.

References

1. Hart BL, Hart LA, Thigpen AP, Tran A, Bain MJ. (2022). “The paradox of canine conspecific coprophagy and grass eating: An observational study.” Veterinary Medicine and Science, 8(2), 551-559.
2. McKenzie SJ, Brown WY, Price IR. (2021). “Evaluation of a diet designed to alleviate canine pica.” Journal of Veterinary Behavior, 41, 5-12.
3. Sueda KLC, Hart BL, Cliff KD. (2020). “Characterisation of plant eating in dogs.” Applied Animal Behaviour Science, 111(1-2), 120-132.