We all know that most fiber isn't digestible to humans. Luckily, we're omnivores, so it doesn't matter much. But other animals do need to break down fiber so they can enjoy its nutrient-rich goodness. For example, cows rely on beneficial bacteria in their multiple stomachs to digest fiber. But have you ever wondered how rabbits digest all the green stuff they eat?

Too bad. I'm gonna tell you anyway.

A rabbit's digestive system isn't that different from ours, except that rabbits have a small bacteria-filled pouch located at the end of their digestive tract. The bacteria break the cellulose down into a digestible form. Unfortunately, because the pouch is at the end of the digestive tract, the broken-down celulose is released as wastes before the nutrients can be fully absorbed.

So the rabbit eats its poo.

The broken-down cellulose goes through the rabbit's digestive system again, and all of the nutrients are fully absorbed. Rabbits smell their wastes to tell if there are still usable nutrients in there.