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Eating poop makes naked mole rats more motherly

If you think you take a lot of crap from your boss, you’ve got nothing on the naked mole rat. Workers in this society literally eat their queen’s dung in order to prepare themselves to care for her children, a new study suggests.

Naked mole rats (Heterocephalus glaber, pictured) live in underground colonies throughout the deserts of East Africa. Apart from a few breeding males, colony members spend their days foraging for tubers, defending against predators, and taking care of the queen’s youngsters. This last behavior has puzzled biologists: In female mammals, child-rearing instincts are typically sparked by a flood of hormones during pregnancy—yet these hormone-producing reproductive organs never develop in the subordinate females in naked mole rat society. So what kick-starts their maternal urge?

According to a study published today in the Proceedings of the National Academy of Sciences, the answer could be related to an unsavory aspect of mole rat behavior: coprophagy, or the eating of each other’s poop. The researchers, who first reported their findings 3 years ago at a Society for Neuroscience meeting, analyzed a naked mole rat colony in a lab. One group of female subordinates dined on the pregnant queen’s dung, whereas another ate poop from a nonpregnant queen. A final group ate feces from a nonpregnant queen that had been garnished with the estrogen hormone estradiol, which has been shown to jump-start maternal behaviors like grooming and nursing.

Subordinates that ate poop either from the pregnant queen or fortified with estradiol turned their heads to tune into recordings of mole rat pup cries, and had higher levels of estrogen in their poop and urine, than did the other mole rats. That suggests naked mole rat queens pass along maternal instincts to their subordinates through fecal meals—a strategy that appears to be unique in the animal kingdom.