Some very freaky researchers at the University of Oxford have discovered that the loudest howler monkeys tend to have the smallest testicles. Someone forward this article to Gordon Ramsay.
The study, which was recently published in the journal Current Biology speculates that this is an evolutionary trade off between larger throats, which result in lounder calls to attract mates and intimidate rivals, and larger testicles, which produce more sperm.
“In evolutionary terms, all males strive to have as many offspring as they can, but when it comes to reproduction you can’t have everything,” said Jacob Dunn, a researcher at the University of Cambridge’s Division of Biological Anthropology. “There is evidence in other animals that when males invest in large bodies, bright colours, or weaponry such as horns or long canines, they are unable to also invest in reproductive traits. However, this is the first evidence in any species for a trade-off between vocal investment and sperm production.”
The study also found that monkeys with louder calls and smaller testicles tend to live in a harem-type setting, with one male shared between multiple females. Males with larger testicles and softer calls tend to live in more of a swinger-style commune, where the females have multiple male partners.
On a side note, since these scientists have time to measure monkey balls, I assume that whole global-warming thing is has been solved.