Why do rabbits eat some of their own feces?

Rabbits consume their own feces, a behavior known as coprophagy, as a vital part of their digestive process to ensure they derive maximum nutrition from their diet.12

Because rabbits are herbivores that consume large amounts of cellulose—a complex plant material that is difficult to digest—they utilize a double-digestion system. Plant material collects in the cecum, where symbiotic bacteria break down the cellulose and produce essential B vitamins.12

The rabbit then excretes soft, black, viscous pellets that contain up to five times the vitamins found in their hard droppings. By immediately eating these soft pellets and redigesting them in a special part of the stomach, the rabbit is able to absorb nutrients that were missed during the initial passage through the gut.12