Scientists are marvelling at a lemur with testicles so large that were a human chap to carry equivalent plums in his trouser department, they'd be the size of a couple of grapefruit.
The average male northern giant mouse lemur (Mirza zaza) tips the scales at just 280g, but has "an average testes volume of 15.48 cubic centimetres", the BBC explains.
Accordingly, "5.5 per cent of the male lemurs’ bodies were testes" by weight, shaming blokes who can boast just 0.05 per cent of their mass dangling between their legs.
This shock revelation is courtesy of Dr Johanna Rode-Margono and Professor Anna Nekaris of the Nocturnal Primate Research Group at Blighty's Oxford Brookes University. Along with Professor Peter Kappeler from the German Primate Center, in Germany's Göttingen and Dr Christoph Schwitzer of the Bristol Zoological Society at Bristol Zoo Gardens, they ventured forth into northwestern Madagascar's Ankarafa Forest, grabbed seven male northern giant mouse lemurs and whipped out the tape measure.
The boffins described the discovery as "especially surprising”, and speculate that "strong sperm competition and polygynandrous mating" may be the explanation. A polygynandrous system, the Beeb notes, is "where two or more males mate with two or more females".
The northern giant mouse lemur - uncommonly among lemur species - mates all year round, meaning it doesn't really need improbably large testicles to compete with other males, which would be the case during a shortened mating season.
However, during their field trip, the scientists found "up to three males sharing a nest with a single female". This lends weight to the idea that "males compete for access to females and may require outsized testicles to give themselves the best chance to fertilise their partner".
In the end, there's still plenty more work to be done before biologists have the complete cobblers picture. Dr Rode-Margono explained to the BBC: "There are still debates whether large testicles are because of a higher amount of sperm, or because of a higher mating frequency."
The full results of the team's enlightening investigation can be found in the American Journal of Physical Anthropology (subscription required). ®