High on the mountain slopes and far beneath the thick rainforest canopy, Odey, the 35-kilogramme Alpha male of a troop of Nigeria's awesome drill monkeys, bares his lengthy fangs and fluorescent penis.

His huge jet black face surrounded by a thin strip of brilliant white fur is contorted into an expression of apparent rage as he barks his disapproval at a rival who has come too close to one of his two in-cycle females.

Sitting bolt upright on a fallen log, legs splayed open, he shows his off-white teeth, his bright pink inner thighs and his slowly flicking vermillion-coloured member.

There is no disputing the fact that today Odey is the leader of his pack.