Goodfellow's tree-kangaroo
They have large stomachs rather like fermentation vats. They use a two-stage process like cows and related herbivores digest food. First the food is softened in one part of their stomach,  and then by passing the material back up and chewing it again, they can return it to a second part of their stomach. This is where bacteria in the stomach's various chambers, breaks down the tough fibers of leaves and grasses.