Definition of Pack animal

Many ungulate species are traditional pack animals, including  elephants, camels, the yak, reindeer, goats, water buffalo and llama, and many of the domesticated Equidae (horse family).

The term is not routinely applied to humans carrying loads on their backs except to make a pejorative point about the injustice of so employing them, or about the privation that usually occasions accepting such work without explcit coercion. (The 1978 Rolling Stones song Beast of Burden refers to a sense of abuse, accepted within a romantic relationship.) Nevertheless, from a physical point of view, certainly many considerations apply equally to human and other pack animals, without considering the range of social conditions ranging through slaves, abused women and children, Himalayan and African natives employed as expedition porters, vacationing students whose duties as staff of mountaineering huts include packing stunningly heavy loads of supplies up steep slopes, and purely recreational hikers and backpackers including both short-trip ones, and long-trip backpackers who court injury and emaciation in carrying their heavy loads.