The second yak was shot in the middle of the day, as you can see by the strong top lighting, but if you get your exposure right, it can work out okay. Looking at the files on my camera's LCD screen, it seemed like I had severely underexposed the photo, but what I had actually done was ensure the top of the yak, the part that's in bright sunlight and highly reflective, was correctly exposed. This meant I could retain some detail there during post-production. Then in Photoshop (or I could have just as easily done it in Lightroom or Capture One), I lightened up the rest of the yak and the result looks okay.
The yak was very happy.
But my question remains, are yaks dangerous?