If your housemates spend their days feeding poop-cakes to your nine hundred children, chances are you're a naked mole-rat. And chances are you’re about to be milked.

Mole-rat milking. It’s a thing. Or at least it is for Smithsonian researcher Dr. Olav Oftedal, who, with help from the National Zoological Park and Auburn University, has conducted a study on mole-rat milk production.Why mole-rats? Like most things in nature, it's all about sex.

Naked mole-rats are eusocial animals, meaning that they live in large groups, work together to take care of their young and divide daily tasks amongst the many members of the colony. This type of communal living certainly isn’t exclusive to mole-rats – but these buck-toothed beauties have taken the 'sharing is caring' approach one step further: by applying it to reproduction. 

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A litter of newborn naked mole-rats huddles inside of their burrow. Image: Edward Russel/Flickr

They are one of only two mammal species (the other being another mole-rat) known to practise eusocial reproduction. Much like a bee colony, a typical mole-rat colony is made up largely of worker rats (about 300) who will never reproduce, accompanied by one to three reproductive males and just one reproductive female – the queen. 

The mole-rat queen has one function within the colony: she's a baby-making machine. Every few months, she will give birth to a litter of 12 pinkies and then swiftly begin breeding again. This lather-rinse-repeat process will go on for the entirety of her 30-year lifespan ... and it leads to the production of more than nine hundred young!

“Although the queen is supported by the rest of her colony, reproducing for the whole colony places terrific physiological demand on the mother,” says Oftedal, noting that this reproductive effort is 60-140 times higher than in any other rodent. “The young start to eat solid foods and beg for faeces from colony members at about two weeks old, but they will continue to suckle for three to four weeks."

'Beg for feces' … we can’t gloss over that one, now can we?

Like many other rodents, naked mole-rats engage in an oh-so-lovely activity known as caecotrophy, which allows them to absorb extra nutrients and minerals by re-ingesting special cakes or pellets that have been digested once, fermented in the hindgut and then expelled by the anus. In other words, they eat their own specially fermented poop – or rather, the colony eats the colony’s specially fermented poop to supplement the diet.

While the workers are busy foraging for food like tubers (and yes, faeces) for the young mole-rats, the queen stays put to nurse the youngsters, which means she loses a lot of energy – fast.

“If you can milk a cow, you can milk a mole rat ... it's just a matter of finding the right gear. Oftedal and his team were up for the challenge.”

The team hypothesised that the secret to so much successful suckling was to produce especially nutrient-rich milk, which would allow the mother to produce it in lower quantities, saving energy. In order to test this, there was only one thing to do: learn how to milk a naked mole-rat.

Oftedal’s interest in lactation has led him to milk some pretty unusual subjects over teh years, including bears and dolphins. While milking something as small as a mole-rat would be no easy task, he was certainly up for the challenge. If you can milk a cow, you can milk a mole rat ... it's just a matter of finding the right gear.

"Milk composition analysis has been accomplished in relatively few species of rodents or other small mammals," he explains. This is because it is extremely difficult to get a large enough sample for accurate testing.

To accomplish this 'teat feat', Oftedal and his team used a perforated steel plate to allow contact between mother and babies to stimulate milk flow. After fifteen minutes of stimulation, the babies were removed, and the team used tiny glass tubes to collect just 44.4 milligrams (just over 0.0001 fluid ounces) of milk per session. To put this into perspective, you would need the milk from about 340 mole-rats to fill just one tablespoon.

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The openings in the tiny capillary tubes used to collect the mole-rat milk samples are just larger than a pinhead. The milk climbs up the tube like it would if you dipped the corner of a paper towel in water. Image: Paul Watson/Flickr.

After over a year of collecting, the team had enough milk samples to analyse and compare them against milk from 20 different rodents. And what they found was a creamy curveball.

Rather than the high-fat, high-nutrient milk they were expecting, they found that baby naked mole-rats prefer to suck down skim milk – high in water and low in energy. Producing such thin milk means the queen has to produce the equivalent of 58% of her body weight per day just to keep her litter fed and happy! 

Oftedal chalks the queen's baby-feeding strategy up to two things: living in an arid environment and the mole-rat’s infamous birthday suit.  

Native to the dry savannah of eastern Africa, the rats spend day and night in deep underground burrows, which very rarely fluctuate in temperature. Because of this, they have abandoned many of the functions associated with regulating heat – like sweating. So a change of only a few degrees is enough to dehydrate an adult mole-rat, and certainly a baby.

“The thin, hairless skin is so translucent that you can see the milk accumulating in the mammary glands,” says Oftedal. It is this thin skin that makes the rats so extremely susceptible to water loss. 

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The mole-rat's thin, translucent skin makes it very vulnerable to water loss and dehydration. Image: Smithsonian's National Zoo, Flickr

More research is needed to confirm this, but we hope to be seeing more mini-milking apparatuses in Oftedal’s future. “It appears the only way these naked babies survive is to consume lots of high-water milk,” he says. "The value of finding organisms that do something very different is that it gives us a new perspective on something that may have broader applications for other species."

Need more mole-rat in your life? Leave it to Ze Frank to have our backs with "True Facts" (NSFW).

Top header image: Smithsonian's National Zoo, Flickr