I photographed this male Gelada Baboon (or Bleeding heart Baboon) at Howletts animal park, in Kent.
Here he is flipping his top lip over his nose in a threat display (basically showing his weapons!), he's also pulling his scalp back to reveal his pale eyelids, sometimes he would do the eyelids but not bare his teeth.
He wasn't distressed during these silent displays (he would even do it while lying on his side) and I used a 500mm + 1.4x lens, so I was a long way away from him.........he's just one testosterone fuelled warrior with no one to fight!
Thanks for looking, cheers! and thanks for comments and votes on my previous pic, it's much appreciated!