Lemur moms carrying males smell different from those carrying females, researchers report.
"This is the first evidence in any animal species that a pregnant mother's scent differs depending on the sex of her baby," said Christine Drea, professor of evolutionary anthropology from Duke University.
Drea and co-author Jeremy Chase Crawford of the University of California, Berkeley used cotton swabs to collect scent secretions from the genital regions of 12 female ringtailed lemurs at the Duke Lemur Centre in Durham, North Carolina, before and during pregnancy.
Ringtailed lemurs produce a musky odour that researchers jokingly refer to as "eau de lemur."
The distinctive scent is a complex cocktail of pheromones and other chemicals that have been shown by previous studies to convey information about an animal's sex, fertility and other qualities.
The chemical analysis revealed that the hundreds of ingredients that make up each female's scent change during pregnancy.
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Expectant lemur moms give off simpler scents that contain fewer odour compounds compared with their pre-pregnancy bouquet - change that is more pronounced when the moms are carrying boys, Drea noted.
The patterns correlate with changes in blood hormone levels. According to Drea, hormones change dramatically during pregnancy and girls and boys affect their mothers' hormones differently.
"The difference in hormone profiles between pregnant lemurs carrying sons and those carrying daughters is dramatic," she said.
The researchers do not yet know why pregnant lemurs produce simpler scents, particularly when they are carrying males.
The findings were reported in the journal Biology Letters.