Many people claim to have seen yetis in the Himalayas. They are supposed to be ape-like creatures with long, shaggy coats. In 1951 photographs of yeti footprints were published but no one has proved yetis exist. It is thought that yetis are, in fact, large black or brown bears. A more unusual explanation is that they are 'visions' or hallucinations caused by a lack of oxygen at high altitudes.