The loudest howler monkeys have the tiniest testicles, a study found.

A study has found that monkeys who scream the loudest also tend to have smaller testes and a shortage of sperm compared to their peers. Howler monkeys are one of the few nest-building monkeys, and one of the loudest creatures in the animal kingdom.

Image credit: Carolyn M. Crockett
Source: cnet.com/news…