Chucks

Chucks are groundhogs the size of a donkey.
They look like a capybara on steroids.
They are herbivores, they can eat almost any plant material, but they prefer starchy roots and tubers.
They live in clans of 5-20 individuals, inhabiting gentle hills and grasslands, and they have managed to survive thanks to their lightning fast reflexes, the burrows they dig and because of their incisives, each the size of a dagger, and quite as sharp.
They are easily tamed, and they are considered extremely useful animals, since they shed fine hair that can be woven into textiles, females produce a milk that can be turned into great cheese, and their meat is remarkably good. Furthermore, they can be used as mounts, and pack animals, although they cannot withstand great weight, since they are mor nimble than resilient.
As mounts, they are in most senses comparable to a horse, but they are faster on short distances, cannot run long distances, they have very good reflexes, and they are well suited for high slopes, rocky terrain and otherwise difficult terrain.
They are usually very social and friendly among them and especially with humans, so much so that even in the harshness of the Afterfall, many people refuse to eat the meat of such noble creatures.