A few fellas from the audience actually let me know that they had colourful genitals already… so maybe this isn’t such an odd adaptation? It was the most popular though, with 60% of the audience opting for this. Hooray, you’re in the majority!
Vervet monkeys (several species within the Chlorocebus genus)
Found throughout sub-saharan Africa, you can’t miss a male vervet monkey… mostly because of their incredible, bright blue, um, scrotum. The blue may vary from a cornflower blue to a chilly white and the exact shade can tell males a lot of information about the health and status of another.
Studies have found these colourful scrotums play an important role at diffusing male-male aggression. If one male can tell another male is more powerful than himself through the colour of his junk – he’s less likely to instigate a fight. This reduces the number of unnecessary injuries and consequently, does help defend male vervet monkeys from their fellow fellas.
Cramer, J. D., Gaetano, T., Gray, J. P., Grobler, P., Lorenz, J. G., Freimer, N. B., . . . Turner, T. R. (2013). Variation in scrotal color among widely distributed vervet monkey populations (Chlorocebus aethiops pygerythrus and Chlorocebus aethiops sabaeus). American journal of primatology, 75(7), 752-762.