Sharing childcare duties helps lemur babies survive, Yale researchers find

Some lemur mothers, like their human counterparts, share child-rearing responsibilities and tend to fare better than lemur moms that go it alone, Yale University researchers have found.

Black-and-white ruffed lemurs which share nests with other mothers have more time to forage for food according to the study published Aug. 6 in the journal Behavioral Ecology and Sociobiology.

“Mothers that cooperate have more time to eat and take care of themselves and, in turn, their offspring are more likely to survive,” said Brenda Bradley, assistant professor of anthropology and co-author of the study.

Ruffed lemurs and humans are the only day-active primates known to use ‘kindergartens,’ or pooling of infants by multiple mothers. The ruffed lemurs of Madagascar are also unusual among primates because they are born in litters and give birth only once every few years. Like human babies, the lemurs are undeveloped at birth and totally dependent upon their mothers. In the weeks leading up to birth, black-and-white ruffed lemur mothers build nests in trees like birds.

“And some mothers — but not all — end up moving in and creating communal nests to cooperatively raise offspring,” said Andrea Baden, post doctoral researcher and first author of the study. “While two or three mothers are off fulfilling other needs, like foraging and socializing, one will stay behind to babysit and protect infants in the nest, including those that are not her own.”

Yale researchers not only observed lemur behavior in the wild but conducted genetic tests on the lemurs to determine whether the nest sharers were related and simply creating a sort of family compound.  Intriguingly, non-relatives and kin both share nests.

Baden would like to study why some mothers chose to raise children alone if there were clear advantages to raising offspring communally.

“It is unclear why some females cooperate and others do not,” Baden said.

Work was funded by: National Science Foundation, LSB Leakey Foundation, J William Fulbright Foundation, Primate Conservation Inc., Conservation International, Stony Brook University, Omaha’s Henry Doorly Zoo, and Yale University.

Other authors were: Patricia Wright, Stony Brook University, and Edward E. Louis Jr., Omaha’s Henry Doorly Zoo.