It's a long held belief that loud mouths overcompensate for something, but in the case of howler monkeys, science has confirmed it's a biological fact.

Howler infant number 5 on the back of a juvenile capuchin carrier, who is using stone tools at an anvil site in a stream bed. Usually, this behavior in females is described as adoption, thought to be ...

A group of male capuchin monkeys kidnapped baby howler monkeys – a different species – on a small island of Panama. Video shows the howler monkeys clinging to the male capuchin monkeys’ backs, but the ...