Infant Lemurs Born to Older Mothers Less Likely to Get Hurt

Research from the Duke Lemur Center in North Carolina suggests that lemur babies born to older mothers are less likely to get hurt than those born to younger mothers.

Researchers made their conclusions after a long-term aggression study that involved 240 ring-tailed lemurs that were monitored daily from birth to adulthood for 35 years.

The research team found that infants born to older mothers were less likely to get bitten, but precisely why this is is still not clear, the researchers reported. It could be that older mothers are better at thwarting aggressive behavior toward their offspring or just generally better at protecting their offspring than younger mothers.

Contrary to most mammals, where males are the most aggressive, bullying-prone sex, in lemurs females are responsible for a great deal of interspecies aggression as well, lunging at one another for first dibs on food and chasing away males at mealtimes.

Of the 237 lemur babies born at the Lemur Center between 1971 and 2006, 15 died before their first birthday because of being bitten.

Researchers analyzed a number of risk factors that might influence how infants fare when caught in an act of aggression, testing for sex, weight, genetic makeup, group size and whether the infant was a twin or a singleton.

But of all the factors analyzed, the age of the mother played the largest role in whether a lemur was injured.

Infant lemurs that avoided injury had mothers that were an average two years older than the infant lemurs who sustained injuries from group aggression. The results were true even for first-time mothers.

Lemur researcher Christine Drea said that more study is needed to learn why maternal age improves the odds of infant survival, but its possible that older mothers are just better at protecting their infants and avoiding fights than less experienced younger mothers.

The research highlights unusual trends in the social order of the ring-tailed lemur.

"Female lemurs are more dominant and aggressive than females in other species, and that puts their kids at risk," Drea said.

Drea and her colleagues' research is published in the journal PLOS ONE.