Colombian woolly monkey
The Colombian woolly monkey is a critically endangered species of woolly monkey from Colombia and possibly also Venezuela. Among all atelinae primates, Colombian woolly monkeys exhibit the most sexual dimorphism in body size. Males are about forty-five percent heavier than their female counterparts. However, the cause of this dimorphism remains an enigma as there are no apparent female choice in favor of larger males. In fact, mating amongst Colombian woolly monkeys is promiscuous in that all adult and subadult males in a group mate with each female in estrous, and male-male rivalries in the context of mating are very rare.
