Bos mutus

Bos mutus is the scientific name for the wild yak. Just like Bos grunniens, the "Bos" means "an ox," however "mutus" means "mute." Although the wild yak does in fact grunt, the domesticated yak tends to be the significantly noisier of the two so it got the name "grunniens."  Some recognize the wild yak as a separate species of Bos grunniens, the domesticated yak, while others consider the wild yak a subspecies of the domesticated yak. Regardless of the specific classification, both the wild and domesticated yak are extremely similar with some notable differences. The wild yak is generally larger than the domesticated yak by even as much as 1,000 pounds in the males. The coats of these to animals can be significantly different as well. The wild yak tends to only have coats of black coloring with occasional brown hairs mixed in.
The domesticated yak can have a coat color that ranges from black to brown or yellow to white, with any range of colors between those as well. The domesticated yak has also been known to occasionally lack horns. This divergence between yaks may have occurred in tangent with the domestication of yaks. When members of the same species are separated for many many years, evolutionary differences will begin to appear separately in each new group. Yaks were first domesticated 4,000 years ago, so for 4,000 years wild and domesticated yaks have been evolving and generally only breeding with members of the same group and passing on their changes until now it appears we may have 2 different species.
Surprisingly, wild and domesticated yaks do not seem to get along when they come into contact. For some unclear reason, wild yaks may attack and even will kill a domestic male yak.
The wild yak population is considered vulnerable to endangered according to research groups. It is a very difficult animal to help because of its isolation in the Himalayas. We may lose the wild yak completely one day.

Go see the other relatives of Bos grunniens on the Classification page. Check out my References or learn About Me.