Monkey roars come with intimate secret

2015-10-22 21:21


Multimedia   ·   User Galleries   ·   News in Pictures Send us your pictures  ·  Send us your stories

Washington - The howler monkeys whose guttural calls reverberate through Central and South American rainforests possess a secret that the males of the species may prefer to be left unrevealed.

Howler monkeys make among the loudest, deepest sounds of any land animal and males use their roars to attract the ladies for mating and intimidate other males.

But scientists on Thursday said they have discovered a curious paradox: males that make the lowest-frequency calls considered the most alluring to potential mates are endowed with the lowest reproductive potential.

The research focused on a cup-shaped bone, the hyoid, located above the larynx that creates a resonating chamber to amplify vocalisations.

Vocal tract

Among nine howler monkey species studied, those with the biggest hyoid produced the deepest and lowest-frequency calls, but also had the smallest testes for sperm production.

"We discovered that the largest hyoid bones were found in howler monkey species with the smallest testes volume and vice versa," University of Utah anthropologist Leslie Knapp said.

University of Cambridge biological anthropologist Jacob Dunn called it an "evolutionary trade-off" for male howler monkeys between vocal tract and testes size.

"This means that different species of howler monkeys either invest in one of these traits or the other, but not both," Dunn said. "I think the main message is that when it comes to reproduction, you can't have everything."

Multiple females

Howler monkeys, found from southern Mexico to Argentina, spend most of their time in tall trees with the help of their gripping, prehensile tails, munching leaves, fruits and flowers. Their howls can be heard 5km away.

Males in species that live in "harem" groups of one male and multiple females have a very large vocal tract but small testes. Males in species with multiple males and females per group have smaller vocal tracts but larger testes.

"This is probably because the females in these species will mate with several males and so the males have evolved to produce more sperm to increase their chances of fertilising an egg," Dunn said.

Read more on:    us

Join the conversation! encourages commentary submitted via MyNews24. Contributions of 200 words or more will be considered for publication.

We reserve editorial discretion to decide what will be published.
Read our comments policy for guidelines on contributions.

Inside News24

Traffic Alerts
There are new stories on the homepage. Click here to see them.


Create Profile

Creating your profile will enable you to submit photos and stories to get published on News24.

Please provide a username for your profile page:

This username must be unique, cannot be edited and will be used in the URL to your profile page across the entire network.


Location Settings

News24 allows you to edit the display of certain components based on a location. If you wish to personalise the page based on your preferences, please select a location for each component and click "Submit" in order for the changes to take affect.

Facebook Sign-In

Hi News addict,

Join the News24 Community to be involved in breaking the news.

Log in with Facebook to comment and personalise news, weather and listings.