Yak Skulls

The basic idea behind the skulls of various animals outside a building is to ward off evil spirits. This is the case with yak skulls as well. The skulls are said to be apotropaic, which means they (are believed to) have the power to avert evil influences or bad luck. When a yak dies the villagers divide the meat among all the members of the village. The head would not be eaten and so would be cleaned and hanged on the walls with the belief of fending off bad spirits. Basically, any skull hung on the entrance gates are to fend off bad spirits, doesn't matter if the skull is a Yak's, a blue sheep's or even your's.