Those incredibly loud howler monkeys that inhabit Central and South American rainforests may be compensating for something.
A new study has found that howler monkeys with the loudest and most guttural calls apparently have the smallest testes as well, according to a Reuters report.
Howler monkeys have certainly earned their name, with the loudest call of any land mammal known on Earth. They have roars that have compared to that of a lion, and it is believed that they have a dual purpose of warding off competing males and attracting a mate.
But as it turns out, a male howler monkey either has one of the most powerful calls around, or regular or large sized testes — but not both.
In a study published in the journal Current Biology, a research team examined a bone above the larynx that helps them to amplify their calls. This bone, called the hyoid, was largest in those with the deepest calls, but it also correlated with smaller testes, meaning the male wasn’t as big of a sperm producer.
It’s an interesting finding because it indicates that there is a trade-off in evolutionary terms for howler monkeys, with some getting better “howls” that help them establish dominance, and some having better reproductive capacity. Each has its advantages, and disadvantages, and it doesn’t appear that they can have both.
Howler monkeys range from Mexico down to Argentina, where they spend most of their lives in the trees with howls so loud they carry up to three miles.
A news release on the findings have been posted on the University of Utah’s website, which can be found here.