When male lemurs are scoping the forest for a new mate, they follow their noses: the rich “scent stew” released by female lemurs can indicate fertility status, their relatedness to other lemurs and even whether they're inbred. But put those females on hormonal birth control, and their chances of being chosen plummets, according to a new study cited by Futurity.org.

Study author Christine Drea, an associate professor of evolutionary anthropology at Duke University, says this finding may explain some of the behavior changes among captive primates that have been treated with contraceptives.

“There’s something very different about these gals,” Drea says. “If animals are figuring out who their kin are by scent, she no longer smells like her brother.”

In the study, 12 females were tested for their attractiveness to males before and after being put on monthly injections of Medroxyprogesterone acetate, marketed as Depo-Provera by pharmaceutical giant Pfizer. The 13 males used in the study showed clear preferences for "intact" females that weren't on birth control.

And though we may not think of ourselves as creatures that rely heavily on scent to find mates, this finding may shed light on human relationships, as well.

“One has to wonder if human mate choice might be affected in some of the same ways it has been in these primates,” says Drea.

Birth control makes lemurs smell funny
Hormonal contraceptives change the smell signature of female lemurs, making them less attractive to potential mates.