Calls vs. balls: monkeys with more impressive roars produce less sperm | University of Cambridge

A recent study found the male howler monkeys with the loudest calls had smaller testes and produced less sperm than their quieter peers, the University of Cambridge reported. This evolutionary "trade-off" between the size of the male hyoid (the hollow throat bone that allows the guttural call to resonate), and the size of the reproductive organs corresponds with the mating systems of different howler species.

The louder primates were also observed wearing Rolex watches and driving Dodge Vipers and Porsche Carreras . . .