Beasts of Burden

Pack Animals

A tame beast can be used as a pack animal. It has an inventory with the listed number of slots based on its size, and it can be leashed to a tree or other sturdy object to prevent it from wandering off.

Mounts

A tame animal of large or huge size can be used as a mount. During overland travel, a party member with a mount can take the march action twice without losing endurance. 

They still lose it as normal beyond that point. Supporting a rider uses five inventory slots, so large and huge creatures still have some space for gear.

Vehicles

Animals can also be used to haul carts, wagons, sleds, and other vehicles. While being used for this purpose, an animal has no inventory; instead, the vehicle has an inventory of a size larger than that of the animals combined. A vehicle can be hauled by one animal of its size, two animals that are one size smaller, or four animals that are two sizes smaller. Characters that haul their own wagon lose 1 endurance after each march.