An insect society, but mammalian
In the arid grasslands of Ethiopia, the naked mole-rat (Heterocephalus glaber) lives a life unique among mammals. It is one of only two mammal species known to be eusocial, meaning it has a caste-based social structure similar to that of ants or bees. A colony, which can contain from 70 to 300 individuals, is ruled by a single, dominant breeding female, the queen. She is the only female that reproduces, mating with a select group of one to three males. Rest of the colony consists of sterile workers with designated roles. There is a division of labor based on size: smaller workers are responsible for gathering food and maintaining the tunnels, while larger individuals act as soldiers, defending the colony from predators like snakes. The queen actively suppresses the reproductive capabilities of other females through behavior, ensuring her genetic dominance. If the queen dies, a power struggle ensues among the subordinate females, with the victor ascending to become the new queen. A new queen's body physically changes; her lumbar vertebrae actually grow longer with each pregnancy, allowing her to carry larger litters without becoming too wide for the narrow tunnels. Litters can average 11-12 pups, but queens have been known to have as many as 27 at once.
Life in the dark
The naked mole-rat is exceptionally adapted to its subterranean existence. These rodents build extensive, burrow systems that can stretch for up to 4 kilometers (2.5 miles) and connect various chambers for nesting, food storage, and waste. They dig with their massive incisors, which are located in front of their lips, a feature that prevents them from ingesting soil. Their wrinkled hairless skin has very few pain receptors, and their eyes are nearly useless. Instead, they navigate their dark world using sensitive whiskers and a keen sense of smell.
The underground environment is hypoxic, with low oxygen and high carbon dioxide levels. Naked mole-rats have a very low metabolic rate, about 70% that of a mouse, and their blood has a high affinity for oxygen, allowing them to thrive where other mammals could not. Their diet consists entirely of underground tubers, large plant roots which they can feed on for years by eating the inside and allowing the outside to regenerate. They get all the water they need from this food source. This harsh environment may have driven the evolution of their extreme longevity and remarkable disease resistance. They live for more than 30 years, an exceptional lifespan for a rodent, and show a deep resistance to cancer.