How do cats and dogs know to eat grass?

Cats and dogs don't actually "know" to eat grass in the same way humans do. They don't learn it from other animals or from us. Instead, it's likely a combination of instinct and physiological needs:

Instinct:

* Herbivores: While cats and dogs are carnivores, their ancestors were likely omnivores, meaning they ate a variety of foods, including plants. This instinct to graze may have been passed down through generations.

* Vomiting: Some experts believe that eating grass triggers vomiting, which can help animals get rid of indigestible materials or parasites in their stomachs.

Physiological Needs:

* Fiber: Grass contains fiber, which can aid digestion and help with the passage of stool.

* Nutrients: Some grasses contain vitamins and minerals that may be lacking in their regular diet.

* Boredom: Some animals may eat grass out of boredom or curiosity.

Important Note: While eating grass is generally harmless for most cats and dogs, it can sometimes cause stomach upset or even poisoning if the grass is treated with pesticides or fertilizers. It's important to ensure your pet has access to safe, untreated grass and to monitor their intake.

Ultimately, the reason why cats and dogs eat grass remains a bit of a mystery. It's likely a combination of instinct, physiological needs, and perhaps even boredom.