Why are yaks called "boats on the plateau"?

Yak has a wide range of eating habits, great strength, good climbing ability and high cold tolerance. A yak used for carrying can generally carry 40 ~ 50 kg, and some can carry as much as 100 kg. Walk 20 ~ 25 kilometers every day without rest. Sometimes you can walk without food or drink for a few days, and you can carry it like a boat on the plateau (15). Yak's toes have tough cartilage, and it can walk freely on rugged mountain roads. Usually, horses run faster than yaks, but in the alpine region with an altitude of five or six kilometers above sea level, horses can't run faster than yaks because of the thin air. Especially in snowfields and glaciers, the speed of yak is more stable than that of horses. When old herders cross snow-capped mountains or glaciers, they would rather ride yaks than horses. Tibetan herders often let yaks go first when mountains are closed by heavy snow. Yaks can use their hooves and mouths to dig up snow and open up roads. Moreover, yaks know the way and are reliable guides for herders. The most interesting thing is that yak can drag its body slowly across the surface of the swamp like a boat when crossing the grassland swamp; If it sinks deeper and deeper, it will automatically stop and find another way. It is precisely because yak has so many advantages that Tibetan herders affectionately call it "Noel" (meaning baby).