The howler monkeys are the noisiest animals on the face of the Earth: they are able to emit cries to 140 decibels in volume -the volume of a gunshot or a firecracker, so to speak.

As you can imagine, the specimens of the male species often use this power to advertise their sexual prowess, throwing shattering eardrums screaming females.
But, with a wonderful twist, scientists have recently discovered that the stronger the screams of a monkey, the smaller the testicles.
A research team associated with the University Cambidge arrived at these conclusions by comparing the size of the attributes of dozens of monkeys with the bones ioidi of their larynx and found an inverse ratio of decibels touched and testicular supplied.
The findings were published today in the journal Current Biology.
"We found that males with one hyoid bigger, thus able to issue lower sounds, have smaller testicles and live in groups with one male and a harem of females reduced," said the anthropologist Leslie Knapp among the authors of the research.
"Males with a smaller hyoid live in groups with several males and have bigger testicles."
According to the research team it is the first evidence of a link between the characteristics of the voice and the production of sperm, and helps explain why the howler monkeys develop contrasting social structures.
Explains Knapp, a noisy monkey and with smaller testes are more likely to develop a harem of females with which to have a unique reproductive relationship.
The quietest monkeys and better equipped, however, tend to end up in larger groups that contain more males and females copulate freely with each other.
In this non-exclusive group, the males compete for fatherhood literally according to their balls.
The more abundant the sperm count of a male, the more likely you can beat the other males who mate with the same female.
In this way, we can say that the howler monkeys have developed two different sexual strategies-one based on the screams, an on-balls with the aim to be mutually exclusive.
Noisy monkeys must have exclusive access to females because otherwise it would be difficult to confront the most equipped counterparts, who are more likely to impregnate a female thanks to more abundant sperm production.
The quietest monkeys are less successful in attracting females with their screams, but are loaded where it counts.
Naturally, and rightly, Knapp invites us not to anthropomorphize that information.
There's a whole world of difference between the howler monkeys and humans, especially with regard to sexual selection.
Yet, research evokes images of guys who drive motorcycles noisy inconceivably, or whistling and shouting when a woman goes by the street.
Far from be manly, this kind of compensation stinks attitudes to other, more delicate aspects.
As the saying goes: empty vessels make a fuss, and it seems especially true when the vessel in question is a pair of testicles.

From Vice