ELi5: How do some animals get enough nutrients out of eating hay or grass or a single variety of leaf for their entire lives?

Question

ELi5: How do some animals get enough nutrients out of eating hay or grass or a single variety of leaf for their entire lives?

In: 293

Answer 1

The structural part of plants is made from a substance called “cellulose”, and believe it or not, cellulose is a carbohydrate. Carbs can be simple like sugar, complex like starch, or very, very complex, like cellulose. (Chitin, the stuff the hard parts of bugs are made of, is also a very complex carbyhydrate.)

So that’s how they are living, off mostly carbs. Every animal has a community of microbes living in their gut which helps them digest stuff, and plant eaters are no exception, having microbes living in their gut that can break cellulose up into simpler carbs that the animal can digest.

In things like cows and caribou and buffalo and stuff, the microbes live in a special stomach called a “rumen”. Termites have amoeba living in their absomen that can break down the cellulose in wood.