Yak is big and strong Tibetan cattle. The lifes of Tibetans always depend on these animal. Yak give them milk, skin, wool and yak is also very strong porter. You can not imagine a caravan of Tibetan nomads without these animals. Nowadays the yak can be "employed" as porters for climbing expeditions. The animals carry the loads of the expeditions to the foot of the mountains and these aproaches can be up to one week long. But yaks need their masters who direct them and take care of them along the aproach march. This are yak drivers, mostly owners of the animals. Carrying loads for expeditions and trekkers is a new opportunitiy for them to earn some money on their traditional way.