Wild yak herds are typically made up of 1 male and 100 females. Tibet nomadic folks say that isn't because of the low male birth rate but because the mothers use their teeth to castrate a large part of kids only to keep the strongest, healthiest ones. The uncastrated males leave the herd and choose one female when the season of pairing comes. Wild yaks have ferocious, jealous and short-tempered disposition. That's why it was made sure that only a few males are kept in order to maintain peace in the herds. Kiangs (Tibet wild asses) are said to have a similar behavior.