A naked mole rat queen relies on her colony to help raise her pups, and she may manipulate their parenting instincts through hormones hidden in her faeces 鈥� exploiting the fact that colony members willingly eat her waste.
Naked mole rats live in colonies in which the queen is the only reproducing female, so she needs听other colony members to help look after the pups. Kazutaka Mogi at Azabu University in Japan, and his colleagues wanted to know whether a pregnant queen could influence the parental instincts of other colony members.
They studied a colony of naked rats with a pregnant queen, and found that the queen鈥檚 oestrogen levels were highest during gestation, and waned as she moved into the postpartum and non-lactating stages. It turned out that oestrogen levels in non-breeding colony members followed the same pattern.
Advertisement
Mogi and his team wondered whether the hormones spread from听the queen to other colony members through her faeces. Many animals eat faeces as a way to have a second go at extracting nutrients from a meal. Naked mole rats do so because their diet tends to include poor quality foods high in cellulose, which means their waste contains plenty of unconsumed nutrients.
Faecal food pellets
To explore the idea, Mogi and his team made food pellets of banana, oatmeal, and faeces from a pregnant queen that they offered to the female colony members. They found that oestradiol, a form of oestrogen, was transferred when the mole rats dined on their queen鈥檚 faeces.
The researchers didn鈥檛 have enough faecal samples to test the effect on male colony members, but Mogi says preliminary studies showed similar results to the females.
The researchers also tested how dining on the queen鈥檚 faeces affected communal parenting behaviour. Mogi and his team placed female colony members in a box with a tube on each end, and played recordings of pup calls through a speaker hidden at the end of one tube.
The mole rats were most attentive to the calls during the queen鈥檚 postpartum stage. They entered the tube with the speaker more quickly and spent more time there searching for the pup. Mogi and his team propose that the queen鈥檚 raised oestrogen levels during gestation trickle down through the colony and influence the parental behaviour of those helping to raise pups.
鈥淚t鈥檚 not a demonstration of such a mechanism, but it raises the very interesting possibility that they might have some way to prime other individuals in the group for a time of pups in need,鈥� says Markus Z枚ttl at the University of Cambridge.
There鈥檚 still the question of how this mechanism would work in a real naked mole rat colony. 鈥淕enerally what you see is they鈥檒l bend over and eat their own faeces, and when pups are in the weaning stage they鈥檒l beg faeces from adults,鈥� says Chris Faulkes at Queen Mary University of London. 鈥淏ut when they become adults, the queen seems to be the only one that actually begs faeces when she鈥檚 pregnant because she can鈥檛 bend over and eat her own.鈥�
Z枚ttl also questions whether the queen could reasonably be expected to provide enough faeces for the entire colony. One queen may produce faeces two or three times a day, but her colony may have around 60 members on average, he says. Faulkes agrees that it would be unlikely a pregnant queen鈥檚 faeces could make its way through the entire burrow. 鈥淚t鈥檇 have to be coming out like machine gun fire to get around the whole colony,鈥� he says.
Proceedings of the National Academy of Sciences
听
