Despite its diminutive stature, the giant mouse lemur has the largest pair of testicles relative to its size among primates, according to a new study.

Researchers from the Oxford Brookes University, the Bristol Zoological Society and the German Primate Center discovered that the northern giant mouse lemur (Mirza zaza), which typically weighs a meager 11 ounces, owns disproportionately-sized genitals in comparison to its body mass.

When put into context in relation to an average-sized human, this means that a 177-pound gentleman would have a pair of testicles as big as decent-sized grapefruits.

In a study featured in the American Journal of Physical Anthropology, the researchers found that this lemur species is capable of reproducing all throughout the year. In fact, adult male lemurs often roam around the wild look for potential mating partners and try to copulate with as many females as possible.

This suggests that the animal's large testicles were developed because of its strong need for sperm in order to beat out other male lemurs in copulating with large numbers of females. Scientists call this promiscuous form of mating as a scramble strategy.

These latest findings show that the northern giant mouse lemur is unique in its mating behavior compared to other species of lemur. Most lemurs follow a strict seasonal pattern for reproduction.

The Bristol Zoological Society's conservation director Christoph Schwitzer said that their study is the first of its kind to study the Mirza zaza on a longer term. He said that the species was first discovered in 2005.

Schwitzer added that since most lemurs face a high threat of extinction, their goal is to collect enough knowledge needed to mitigate the situation. He said that the discovery of the northern giant mouse lemur's massive-sized testicles was more of a secondary result of their study.

"We always found it odd that they are called 'giant' mouse lemurs when they belong to the family of the dwarf and mouse lemurs," co-author Johanna Rode-Margono said.

"But now we can say that we now know why—giant was not referring to their body size."

In 2014, the International Union for Conservation of Nature (IUCN) included the northern giant mouse lemur on its Red List as an endangered species because of a reduction in its population due to the destruction of its natural habitat.

Photo: Bernard Dupont | Flickr

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