Working as an au pair is often considered a great way to earn money and travel the world.
The pay is crap, sure, but you can take comfort in the fact you’re not a naked mole rat. It turns out their queens literally feed their workers faeces dosed with hormones to encourage them to look after their young. (Shouldn’t they unionise or something?)
Naked mole rats might not be the prettiest of animals, but what they lack in aesthetics they earn back in astounding brute resilience.
If that’s not hardcore enough, these oddball mammals live in ‘eusocial‘ colonies like some kind of giant wrinkled ant, with a single queen popping out the babies and a bunch of female workers raising the newborns in their nursery.
Because, really, like a naked mole rat is going to care about what you think.
How the queen convinces other female naked mole rats that they should care for her brood when they lack maternal instincts has never been clear, so a team of Japanese scientists set out to find the physiological mechanisms responsible.
It’s already known that concentrations of the female sex hormone estradiol increase in the queen’s faeces after she’s given birth.
Since other females in the colony have undersized ovaries – an organ that produces estradiol – it was hypothesised that somehow this external shot of estradiol might play a role. The most logical way (to us at least) would be through scent.
The only problem is naked mole rats don’t have fantastic vomeronasal organs, meaning detecting the volatile compound in the air could be ruled out.
The most likely way, then, for that hormone to get from A to B was for it to be ingested.
To be fair, while we all just pulled that face, coprophagia, or poop eating, is pretty common throughout the animal kingdom. Even among mammals like naked mole rats.
So to test their idea, the researchers fed one group of subordinate females poop ala pregnant queen, while another were served a few scoops of plain old non-pregnant faeces pellets.
A third group received a special recipe of non-pregnant-queen faeces drizzled with estradiol. Just like mum used to make.
During this nine day unsavoury diet, the workers were exposed to the recorded sounds of naked mole rat pups begging for attention.
None of them seemed to pay the vocalisations much attention, at least at first. This all changed four days after the feeding period, when those fed the pregnant queen’s faeces started to act differently, spending more time near the recordings.
The same went for those fed the poop artificially laced with estradiol, emphasising the hormone’s likely role in the change in behaviour.
Ingesting the sex hormone increased the workers’ estradiol levels, at least for a while. Just long enough to get clucky over the newborns and give them plenty of licking and warm snuggles.
If this all sounds particularly gross, rest assured the naked mole rats are probably making do with a rather extreme living situation.
There’s not much ventilation down in their burrows, and limited food resources make coprophagia an appealing choice in the face of starvation. This unique communication system might be a clever way to adapt to harsh living conditions.
It’s also not like every member of the colony is drugged into nursery duty. The pregnant queen would probably keep to her nesting area, meaning just a few special workers hanging around nearby would have access to her special pellets of baby-love.
We’re not sure if this makes naked mole rats more or less appealing. It does raise some sympathy for those poor little infants though!
Good thing their sense of smell is bad.
This research was published in PNAS.