The scat contains the sex hormone estradiol, which turns regular mole-rats into caregivers
Dealing with poop is an unavoidable hazard of raising children, regardless of species. But for naked mole-rats, that wisdom is especially salient.
During pregnancy, the scat of a naked mole-rat queen — the only female in the colony that reproduces, giving birth to a few dozen pups each year — contains high levels of the sex hormone estradiol. When subordinate female naked mole-rats eat that poop, the estradiol they pick up cues them to snap into parenting mode and care for the queen’s offspring, researchers report the week of August 27 in the Proceedings of the National Academy of Sciences.
In colonies of naked mole-rats (Heterocephalus glaber), lower-ranking females don’t have developed ovaries and don’t reproduce. They also don’t experience the pregnancy-induced hormonal shifts that usually cue parenting behaviors, yet they still care for the queen’s babies.
Researchers gave poop pellets from nonpregnant queens to subordinates for nine days. One group got pellets with added estradiol, to mimic pregnancy poop. Levels of estradiol increased in the dung of subordinate females that ate the hormone-packed pellets, suggesting that scat snacks could induce measurable hormonal changes. And those mole-rats were more responsive to the cries of pups than those that didn’t get the hormone boost, the team found.
The poop may not be directly shared with the whole colony, study coauthor Kazutaka Mogi, a developmental biologist at Azabu University in Sagamihara, Japan, says. Instead, the handful of mole-rats spending the most time in the queen’s nest are probably eating her scat. Others in the colony might be exposed to estradiol by eating the scat of subordinates who ate the queen’s poop, he suggests.
A. Watarai et al. Responses to pup vocalizations in subordinate naked mole-rats are induced by estradiol ingested through coprophagy of queen’s feces. Proceedings of the National Academy of Sciences. August 27, 2018. doi: 10.1073/pnas.1720530115.