Costa Rica’s howler monkeys are the least loud but most well-endowed

October 25, 2015
1 Comments

For male howler monkeys on the search for a mate, size matters; but being a well-endowed monkey comes at a price. The results of a new study show that in some species of howler monkeys the larger a monkey’s testicles are, the smaller its voice.

This might seem like an easy trade-off, but howler monkeys are the world’s loudest land mammals, capable of emitting roars of up to 140 decibels. The monkeys use their intimidating roars to locate one another, scare off predators and, for certain species, as mating calls.

In the paper, published in Current Biology this month, researchers looked at nine species of howler monkeys found throughout Central and South America. They measured museum samples of each species’ hyoid bones, which in live monkeys sit next to their vocal chords and serve as amplification chambers, and compared these measurements with the size of the testicles of monkeys in zoos.

The average results showed a clear correlation across species, but monkeys were not studied individually.

The howlers found to have deeper calls belonged to the more competitive species. These monkeys favor a big voice to attract far-away females and scare off rival males. The monkeys with larger testicles belonged to species where females mate with more than one male, and a high sperm count influences the likelihood of the male successfully fertilizing a female’s egg.

The reason howlers don’t have both large testicles and a big call seems to lie in the amount of energy required to develop either trait as it grows up.

The mantled howler monkey (Alouatta palliata), the only species of howler found in Costa Rica, was found to have the wimpiest call, but the largest testicles of any of the monkeys studied.

You may be interested

New poll in Costa Rica shows huge surge for evangelical pastor
Elections 2018
1341 views
Elections 2018
1341 views

New poll in Costa Rica shows huge surge for evangelical pastor

AFP - January 23, 2018

While nearly a third of Costa Rican voters remain undecided less than two weeks before the presidential and legislative elections,…

Tamarindo gears up for Art Wave Festival
Arts & Culture
663 views
Arts & Culture
663 views

Tamarindo gears up for Art Wave Festival

Ellen Zoe Golden - January 23, 2018

Tamarindo is preparing for another cultural immersion: the 2018 Tamarindo Art Wave is coming to town on Jan. 25-27. This…

VIDEO: Will Costa Rica recognize this same-sex marriage?
Human rights
1659 views
Human rights
1659 views

VIDEO: Will Costa Rica recognize this same-sex marriage?

Elizabeth Lang - January 22, 2018

The Inter-American Court of Human Rights (CIDH) ruled Jan. 9 that all member states, including Costa Rica, must recognize same-sex…