Mammals
Naked Mole-Rat
Heterocephalus glaber · also called sand puppy, desert mole rat
The naked mole-rat looks like a mistake and behaves like a rewrite of the rulebook for mammals. It is nearly hairless and nearly cold-blooded, it lives in insect-like colonies ruled by a queen, it shrugs off acid and low oxygen, it barely gets cancer, and it can live for more than three decades without appearing to age.
Overview
Naked mole-rats live entirely underground in the hot, arid grasslands and semi-deserts of the Horn of Africa, in soil hard enough to require serious excavation. A single colony of up to a few hundred animals maintains a sprawling network of tunnels — kilometres in total — connecting foraging areas, a communal nest chamber, and dedicated toilet chambers. They almost never come to the surface, and when they do it is briefly and at night.
A society with a queen
Naked mole-rats are eusocial — a social structure otherwise found in ants, bees, termites, and only one other mammal. Each colony has:
- One queen, the sole breeder among the females, who grows physically larger over her reign by lengthening her spine and can produce a litter every 11–12 weeks, up to ~28 pups.
- One to three breeding males.
- Everyone else — non-reproductive workers who dig, forage, transport pups, and maintain the nest, and larger soldiers who guard against snakes and raiding colonies. Their reproduction is suppressed by the queen; if she dies, several females fight, sometimes to the death, to replace her.
Rewriting mammal biology
- Temperature. Its body barely thermoregulates, tracking the burrow’s stable temperature; it huddles or basks to adjust, like a reptile.
- Oxygen. It survives hours at 5% oxygen and minutes at zero, switching to an oxygen-free, fructose-burning metabolism.
- Pain. It feels no pain from acid or from capsaicin, because the relevant pain-signalling pathway is disabled — an adaptation to a CO₂-acidic burrow atmosphere.
- Ageing and cancer. It shows essentially no increase in mortality risk with age and almost never develops tumours, thanks to a distinctive protective molecule in its tissues and enhanced cellular defences.
Diet
Naked mole-rats eat large underground storage tubers — some weighing many kilograms — which they hollow out from the inside, leaving the skin intact so the plant survives and keeps growing, effectively a renewable larder. Foraging workers dig blindly toward these tubers, and finding scattered ones efficiently is a major reason cooperative colony living pays off.
Status
The naked mole-rat is Least Concern and common within its range, with no significant threats. Its scientific value is enormous: it is a leading model for research into ageing, cancer resistance, pain, stroke and oxygen deprivation, and the evolution of social behaviour.
Naked Mole-Rat: common questions
Is the naked mole-rat really a "cold-blooded mammal"?
Nearly. Almost alone among mammals, it barely regulates its own body temperature — its metabolism runs low and its body stays close to whatever the burrow is, usually a stable 28–32 °C a metre or two underground. When it needs to warm up it huddles with colony-mates or basks in a shallow, sun-warmed tunnel, behaving more like a reptile. This slashes its energy needs, which suits life on a scattered, hard-won diet of tubers.
Why does the naked mole-rat live in colonies like ants or bees?
It is one of only two known eusocial mammals (the other is the Damaraland mole-rat). A colony has a single reproductive queen and a few breeding males; every other member is a non-breeding worker or soldier, its own reproduction suppressed by the queen's behaviour and scent. Workers dig the tunnel network, forage for tubers, carry pups, and keep the nest clean; soldiers defend against snakes and rival colonies. This system likely evolved because digging burrows in hard, dry soil to find widely spaced food is far more efficient as a large cooperative group.
Do naked mole-rats get cancer?
Almost never, which is why they are studied so intensively. Their cells produce an unusually large, "sticky" form of hyaluronan that seems to stop cells from crowding and turning cancerous, and they have extra tumour-suppression mechanisms. Combined with cells that resist damage from unstable oxygen molecules, this contributes to a lifespan of 30-plus years with, remarkably, no measurable rise in the risk of death as they age — they do not appear to "grow old" in the usual sense.
How do they survive with so little oxygen?
A crowded burrow deep in packed soil can become very low in oxygen and high in carbon dioxide. Naked mole-rats tolerate levels that would kill a human or an ordinary rodent in minutes. At zero oxygen, their metabolism switches to burning fructose instead of glucose — a pathway that does not need oxygen and that is otherwise mainly seen in plants — letting the animal enter a suspended state and recover fully once air returns.