🎓 On Mammals With the Social Structure of Ants
Reflections on seeing naked mole rats on my last trip to the National Zoo.
Back in May1, I went to the Smithsonian National Zoo in DC with my husband, kids, and a family friend. It was a great experience, but my favorite part was seeing the naked mole rats. Naked mole rats are one of my top ten favorite animals, and when told this to my friend, it turned out the only thing she knew about them was the bits that show up in that Kim Possible cartoon.
I love them not because they’re small and ugly cute but because they’re eusocial, which means they have a “queen-based” reproduction structure similar to ants and bees. They live underground in African deserts, eating tubers deep underground. At the zoo, they’re in glass burrows similar to ant farms. When I was visiting, most of the colony was asleep in one chamber, piled on top of each other in a creepy little squirming heap. One little naked mole rat off by itself in a separate chamber, alone, so skinny and emaciated that I assumed it was dead until my friend finally caught it breathing and called me over.
It was a really memorable experience, and maybe you do not know much about them either. So let me tell you about mammals that run their societies like ants.
Why they matter
Naked mole rats aren’t just neat because they’re eusocial. They actually live far longer than you’d expect for a rodent their size. Generally speaking they easily go past 30 years, with records approaching 40, which makes them the longest-lived rodent known.
They are also strikingly resistant to cancer. One mechanism is that their tissues are loaded with an unusually large form of hyaluronan that makes their cells stop dividing as soon as they get crowded. In 2023, a team put the mole-rat version of the hyaluronan-making gene into mice and the mice got healthier and lived longer, which hints that the trick can travel across species.
Then there’s suffocation. In lab tests, naked mole-rats can tolerate hours of very low oxygen and survive about 18 minutes of total oxygen deprivation without apparent injury. Their brains apparently switch to burning fructose, a metabolic move otherwise associated with plants and that I had never heard of before I started the research for this article.
What “eusocial” even means
Eusociality is the social pattern of ants, termites, and a lot of bees and wasps where reproduction is concentrated in a single breeding female and a few breeding males. Everyone else works without reproducing. There is usually cooperative care of the young, and overlapping generations all living together. The naked mole-rat (Heterocephalus glaber) was the first mammal like that found, and its relative the Damaraland mole-rat (Fukomys damarensis) is still the only other mammal I’m aware of that even comes close to it. The rest of the genus involves several species that live in family groups with a single breeding pair and a crowd of non-breeding helpers, and whether they qualify depends on where you draw the line between “true” eusociality and very intense cooperative breeding. Reproductive skew is really more of a spectrum, it’s the spread between who breeds and who does not: in some species a handful of individuals do most of the breeding while the rest do none.
For example, I ran into a milder version of this when I wrote about wild horse societies. Research on feral herds found about 7% of males siring 44% of foals; in natural herds structures, bachelor bands give the surplus non-breeding males somewhere to go, although gelding adds some quirks.
Horses handle the surplus-breeder problem socially, by pushing young males out into bachelor bands until one is strong enough to win a harem. Naked mole-rats handle it physiologically, by switching subordinate reproduction off at the hormonal level and keeping the non-breeders home as labor. They take reproductive skew to its mammalian limit.
In subordinate females, luteinising hormone stays low and the pituitary stops responding normally, so they do not ovulate. This leaves most of them in something close to a prepubertal state for their entire lives. Where the block actually sits is disputed, but at a level of detail I don’t have the expertise to parse. What matters is that subordinate females carry egg precursor cells that sit dormant and only begin dividing once a female makes the transition to queen.
The queen is physically impacted by the role. With each pregnancy the spacing between her vertebrae increases and her body lengthens, so she can carry larger litters over time, starting at roughly 10 to 15 pups and moving up to about 30 in a big female.
Where the ant analogy breaks down
Interestingly, when a queen dies, these hormonal brakes come off several females at once. Researchers at Brookfield Zoo pulled a colony’s queen and breeding male and watched three non-breeding females sharply increase their rate of aggressive shoving within two months, with ovulatory function confirmed by histology in two of them after fatal fights; shoving is a specific dominance behavior that, before the removal, only the queen performed. For a long time, people thought that when a queen dies, the colony erupts into a violent free-for-all, with subordinate females fighting, sometimes fatally, over the vacancy. Then in 2026 researchers reported a colony in which a subordinate female took over reproduction peacefully, with no war at all, after years of disruption that included a forced move to a new facility.
Apparently body size decides the winner more than standing rank does. The Smithsonian’s curators describe dominant females using their relative size to fend off challengers, with a challenger sometimes inflicting fatal damage on the queen.
This is a different arrangement from insects, where caste is fixed before adulthood. The handover is slower, too, because while progesterone climbs within days of a female being released from suppression, breeding rarely follows in less than five or six months.
So not everyone is comfortable filing mole-rats under eusociality in the strict insect sense. Their workers are not permanently sterile the way many insect workers are, a subordinate can become a queen if the spot opens up, and one study of Damaraland mole-rats argued that those breeders at least do not actually depend on helpers to reproduce or survive, which is awkward for the strong obligate-caste reading. So some researchers would rather call them extreme cooperative breeders than true eusocial animals. Personally I think it’s a semantic argument that only matters to scientists, like whether a tomato is a fruit or a vegetable, Eurasia is a continent, or fish really exist.
Convergent evolution is when unrelated lineages arrive at the same solution independently, the way birds, bats, and insects all evolved wings without inheriting them from a single winged ancestor. It seems to me that, although classification is hard and the two eusocial mole-rats did not inherit their queen-and-workers arrangement from a shared eusocial ancestor and do not match their insect parallels exactly, it’s close enough to count. If nothing else, “extreme cooperative breeders” makes them sound more like wolves than ants, and to me, they’re pretty friggin’ close to ants.
They even live in underground tunnels! Digging tunnels after scattered tubers in hard, dry African soil is expensive and dangerous for a lone animal, so staying home and helping your sister breed can beat striking out alone. Put a defensible nest, costly foraging, and a payoff for cooperation in front of a rodent and an ant, and you get remarkably similar caste solutions out of animals separated by hundreds of millions of years of evolution. Just because they aren’t exactly the same doesn’t mean we can’t notice they belong in the same category.
I’m curious whether you agree, tho.
I don’t like to dwell on big “I’m sorry it’s been so long since I wrote” things, but as crazy as it sounds, I had had less time to write than normal because I have been spending much less time at my desk due since I left Readwise. As a result, my back doesn’t hurt as much as it used to and my exercise habits are getting a little better. Separately, the kids’ summer camps and daycare situations have been whacky over the summer for a variety of reasons. That said, I have a post scheduled for next week, ideas for more, and I’m hoping that my posting schedule gets back to normal in the fall when school’s back in session.