Male vervet monkey with blue gear

Male vervet monkey (Chlorocebus pygerythrus) perched on Large-fruited Bushwillow tree and exhibiting proudly its bright turquoise blue scrotum. The blue colour is due to Tyndall light scattering effect over a layer of melanin in the dermis of the scrotum. The vividness of the blue pales when the animal falls in social rank. DOI: 10.1159/000459974