杏吧原创

My, what big eyes you have. And that鈥檚 not all that鈥檚 big apparently鈥� (Image: Melanie Seiler)

Zoologger is our weekly column highlighting extraordinary animals 鈥� and occasionally other organisms 鈥� from around the world

Species: The northern giant mouse lemur (Mirza zaza)
Habitat: Ankarafa Forest in Sahamalaza National Park, Madagascar

鈥淥h my god! How do they manage to walk and climb without bumping these things onto every branch?鈥� asked the first time she saw the testicles of a giant mouse lemur close up.

In turns out they don鈥檛. They stumble and bump their balls with almost every step they take, she says.

At a mere 300聽grams, the northern giant mouse lemur is roughly squirrel-sized. But for its size, this nocturnal lemur has the largest known testicles in the primate world.

If we humans had the same testes size, relative to our weight, an average man would have balls as big as grapefruits, says Rode-Margono, who is at Oxford Brookes University, UK.

Banana bait

Until recently, little was known about this endangered lemur鈥檚 private life 鈥� it was only discovered in 2005.

So Rode-Margono鈥檚 team set out to study wild lemurs in their native habitat in the Ankarafa forest in Madagascar. To learn more about their behaviour, in 2010, her team used banana bait to lure eight animals to a live trap and then fitted them with radio tracking collars.

This allowed the team to follow the nocturnal activity of the primates for three months and recapture them. They looked at how much the size of their bodies and testes changes over time, over what would be the run up to the suggested breeding season for these lemurs 鈥� July to August.

No, that鈥檚 not its thigh (Image: Melanie Seiler)

Those gargantuan testes stayed the same size, which surprised the team. Most lemurs, which are found only in Madagascar, have set breeding seasons. Their offspring are born in plentiful times, when food is easily available.

During the breeding season, the testicles of male lemurs enlarge because they are engorged with sperm, but afterwards they shrink back to normal.

The unchanging hugeness of the testicles of the northern giant mouse lemur suggests that they mate whenever and wherever they can. 鈥淢ales aim to mate with as many females as they can find,鈥� says Rode-Margono.

Their night-time escapades remain fairly mysterious, though. The team saw only a single couple copulating, although they did catch them at it three times.

Fuelling the sex drive

The availability of food may be what allows this species to avoid seasonal mating, says Rode-Margono. The unique climate in the Sahamalaza region, which sits between evergreen rainforests to the north and dry deciduous forests in the south, allows many trees to keep their leaves throughout the year, meaning the availability of food doesn鈥檛 have to limit the sex.

But constant copulation isn鈥檛 going to be enough to keep these lemurs going. Lemurs are one of the most endangered groups of vertebrates in the world, with more than 90 per cent of species considered threatened with extinction, including the northern giant mouse lemur.

Their natural forest habitat is shrinking fast because of destructive agricultural practices and illegal logging. Today, only 10 per cent of it remains, says Rode-Margono.

She estimates that there may be fewer than 17,000 of these lemurs left, and says more research is needed to raise awareness and point to strategies needed to protect them.

鈥淢aybe the large testicles are only a fun fact for some people,鈥� she says, 鈥渂ut for us it also means that we get more people interested in the conservation of these fascinating and unusual primates.鈥�

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