Confirmed: Monkeys with smaller testicles roar the loudest

It’s long been suspected that loudmouths are trying to overcompensate for their inadequacies elsewhere.

Now scientists have found that particularly loud howler monkeys, which are among the noisiest animals on the planet, have smaller testes and produce less sperm than their quieter peers.

But rather than making them less successful mates, the louder members of a group are more likely to have the pick of the females in what the researchers call a ‘harem’ social model.