With even ultrasounds not getting it right all the time, the only real way to tell a baby's gender is after it is born. In lemurs, however, it's possible to tell if a female is pregnant with a boy or a girl depending on the mother's scent.
In a study published in the journal Biology Letters, researchers report that lemur moms smell differently depending on whether they are carrying boys or girls. The study represents first evidence that a mother's scent changes in accordance to the sex of her baby.
Christine Drea from Duke University and Jeremy Chase Crawford from the University of California, Berkeley, worked with 12 ringtailed lemur females from the Duke Lemur Center in North Carolina, collecting scent secretions from the lemurs' genital area before and during pregnancy. About the size of cats, ringtailed lemurs produce a characteristic musky odor.
This distinct scent is made up of pheromones and other chemicals that previous studies have shown to be used in conveying information about a lemur, like its sex and level of fertility as well as other qualities. In Drea and Crawford's study, a chemical analysis with the help of mass spectrometry and gas chromatography showed that the hundreds of components that comprise a female lemur's scent undergo changes when the lemur becomes pregnant.
Specifically, an expectant lemur mom gives off a simpler scent containing fewer compounds compared to the odor it had pre-pregnancy. However, the drop in a scent's intensity is more pronounced when a lemur mom is carrying a boy.
"Such olfactory ‘signatures' of pregnancy may help guide social interactions, potentially promoting mother-infant recognition, reducing intragroup conflict or counteracting behavioral mechanisms of paternity confusion; cues that also advertise fetal sex may additionally facilitate differential sex allocation," explained the researchers.
Additionally, the patterns the scent changes make correlate with fluctuations in hormone levels in the pregnant lemurs' blood. Hormones naturally change during pregnancy but just what these changes are depend on the baby lemur's gender.
"The difference in hormone profiles between pregnant lemurs carrying sons and those carrying daughters is dramatic," said Drea.
She added that different compounds are maybe being produced in the bodies of pregnant lemurs because carrying a boy or a girl calls for different bodily requirements, with compounds being directed away for use in other purposes.
The study was supported by the Research Council of Norway, UC Berkeley, the National Evolutionary Synthesis Center and the U.S. National Science Foundation.
