Question

why does herbivores animals have bigger intestine than carnivores animals?

Answer 1

Since plants contain a lot of indigestible fibres, and so as to obtain the nutrients, herbivores must use the bacteria that live in their gut to break down cellulose and other materials.

Answer 2

Herbivores eating grass need a longer small intestine to allow the cellulose to be digested. Whereas Meat is easier to digest, hence carnivores like tiger have shorter small intestine.