Human testicles are much smaller, in proportion, to some of our primate cousins. Evolution can tell us why. But the size of ...

Colobus testicles weigh just 3 grams. The testicles of the macaques, in contrast, are a whopping 48 grams. You could come up with several believable explanations for their different testicle sizes.

The Caldwell Zoo announced Tuesday they have three brand new additions to their animal family. On Monday evening, zebra ...

Colobus testicles weigh just 3 grams. The testicles of the macaques, in contrast, are a whopping 48 grams. You could come up with several believable explanations for their different testicle sizes.

Zoo guests to Utah’s Hogle Zoo can now visit a male baby colobus monkey, born on March 30, 2025, to mom Violet (11) and dad Sefu (17). Violet came to Hogle Zoo in 2017 on a breeding ...

MEMPHIS, Tenn. - A monkey escaped containment briefly Friday, the Memphis Zoo confirmed. The male colobus monkey, named "Rajesh 'Raj' Koothrappali, PhD" after the character from "The Big Bang ...

Morgan, a 30-year-old black-and-white colobus monkey and patriarch of his troop, was euthanized at Dickerson Park Zoo due to age-related health decline. The decision was made to ensure Morgan's ...

Black-and-white colobus monkey Morgan yells in this undated picture at Dickerson Park Zoo in Springfield. Morgan was euthanized on June 10, 2025, at age 30 due to age-related health issues, the ...

Human testicles are much smaller, in proportion, to some of our primate cousins. Evolution can tell us why. But the size of other body parts is a little bit more of a mystery.

But perhaps the most plausible explanation relates to the way they mate. A male colobus monkey competes ferociously for access to a harem of females who will mate exclusively with him.

You could come up with several believable explanations for their different testicle sizes. Large testicles might be the equivalent of the peacock’s tail, not useful per se but attractive to females.

A male colobus monkey competes ferociously for access to a harem of females who will mate exclusively with him. ... A male macaque with large testicles should make more sperm, ...