Naked mole rats are one of the weirdest mammalian species out there, even when you take out the fact that they are completely hairless. They have a very high pain tolerance, can survive 20 minutes without any oxygen, they do not age, and they are immune to cancer. As if that wasn’t enough to make them stand out, they are also very eusocial and they kidnap each other’s babies and enslave them.
Naked mole rats are fairly small in size (about 4 inches) but they have giant colonies composed of as many as 300 workers. This is the largest colony size among mammals. Furthermore, most of the members of these colonies are sterile, just like the members of bee and ant colonies. The colonies have one queen that reproduces, and she will claim that position by murdering any competitors. Any losers in this struggle for dominance will become subordinate for life, and they will take their directives from the queen by eating her hormone-laced faeces.
Given only one queen, and such a large colony size, biologists believed that inbreeding played a part in the development of the colony. However, this is now believed to be unlikely. In the early 90s, biologists conducted a study in Kenya, where they found that 26 naked mole rat colonies expanded their burrows into neighboring territories. 13 of the colonies that were invaded had been basically completely wiped out.
A year later, the researchers found two pups in one of the original 26 invading colonies that had the characteristics of mole rats from one of the colonies that had been invaded and exterminated. Baffled by this result, the biologists conducted genetic analysis of the tissues they had collected and confirmed that they were indeed a part of that family tree.
It turns out that the invading colony kidnapped pups and turned them into non-reproductive workers. This was the first time that this behavior had been witnessed in the wild. Kidnappings have happened in laboratory settings, however scientists could not determine if this was a natural behavior or if it was determined by the unnatural conditions of the lab.
Kidnapping is a behavior also witnessed in some primate species, but researchers believe that the mole rat behavior has a stronger link to the kidnapping seen in slave-making ant species such as Formica sanguinea. These ants will also take larvae and pupae of other colonies and species and integrate them into their workforce.
So how could a mammal have more in common with an ant than a primate? Biologists call this convergent evolution, where evolutionary pressure creates the same behavioral and physical features in completely separate species. Given the harshness of the environment in which both the naked mole rats and ants live in, it makes evolutionary sense to spread the reach of a colony for kilometers on end if need be, and if you come across another colony, it makes sense to snatch their pups and supplement your workforce. After all, the pups will be sterile and their genetic heritage will not be passed on through your colony.