Camels of the Old World and the New World have provided the indigenous human population with meat, milk, fibre and fuel, also serving as beasts of burden to carry loads, for millennia. With the advent of motorized vehicles, the use of camelids became obsolete except in isolated situations. The numbers of camelids diminished dramatically. A reversal of that trend is now occurring, with a recognition that these animals still function in their respective environments better than any other species of livestock. Camelids have always been popular animals in zoos. Camels and two of the South American camelids are domestic animals which adapt well to contained management. They have a unique ability to obtain nourishment from harsh forages. Their reproductive physiology is different from that of any other livestock species.