Blue Wildebeest

I saw hundreds of these in Namibia, but I found it nearly impossible to get the eye in focus and with a catchlight. I think it has something with head structure, the eye placed much higher on the face and closer to the ear than other mammals. I'm also curious about the fleshy black disc a few inches below the eye; I have no idea what it is. I wonder if the autofocus locked onto that structure instead of the eye in some instances. Given those previous difficulties, I'm very happy with this result!

Etosha National Park, Oshikoto Region, 8/22/22
Canon 600mm f/4 IS II + 1.4x III on EOS R5
1/2000 at f/8, ISO 640