I remember when I first learned that a rabbit ate its food twice.
This curious dietary practice, called coprophagy, is something I'd witnessed as a child raising my own rabbits and guinea pigs in the backyard. Disgusted by the sight of my pets eating their own feces, I recall trying to keep their cages as clean as possible. Had I known better, I would not have been so quick to remove droppings from their cage because I might've put these animals at risk for nutritional deficiency (1-2). Luckily, I wasn't ever very consistent at keeping their cages clean all the time.
Rabbits and guinea pigs, as it turns out, need to eat their own droppings because they provide a valuable source of nutrients like vitamin B12. In the wild, they will normally leave soft droppings at the mouths of their burrows while they go off foraging at dawn or dusk. When they've had their fill of foliage, they return and -- far from being repulsed by having a stack of droppings at the foot of their doorstep -- they eat up these droppings, which are by this time a nutrient-rich fermented dessert.
