The Northwest of Sichuan was part of Kham, one of the three Tibetan Provinces until 1965. Almost 80% of the population is Tibetan.
Yaks, like camels in the desert and reindeer in the tundra, are essential to the survival of the Tibetan. They are used as pack animals and in food (butter, butter tea, tsampa : mixture of barley flour and butter etc).
They practice celestial burial. The body of the deceased is placed on a flat stone. A monk sings around the body, then the Rogyapas notch it. Once the flesh is eaten by vultures, the Rogyapas grind the carcass that is mixed with barley flour and yak milk. Then the vultures finish to eat the body. The origin of celestial burial is first for practical reasons. Tibet has only a few trees, so there’s no wood for pyres; it is also mountainous, it is difficult to bury a body. Moreover, Tibetans are Buddhists, and feeding the vultures is a way to return to the nature.