Lemurs on contraceptives don’t smell right

WILLIAMSBURG, Va. — Putting a female lemur on birth control turns her normally informative scents to nonsense, researchers report.

Doses of Depo-Provera, a common contraceptive for people, shift the odor secretions of female lemurs so dramatically that their scents no longer give clear cues to kinship, identity and genetic quality, says study coauthor Christine Drea of Duke University in Durham, N.C.

A female lemur whose hormones are disrupted by contraceptives may have real trouble attracting a compatible mate, Drea said July 26 at the annual meeting of the Animal Behavior Society.

As for people, men and women might not think they’re influenced by each others’ scents, but “Oh, we are!” said behavioral biologist Susan Jenks of the Sage Colleges in Troy, N.Y., after Drea’s presentation. If women react to the hormones the way lemurs do, “maybe you don’t want to be on contraceptives when you’re picking your mate.”

Also, said behavioral ecologist Jill Mateo of the University of Chicago, “For any zoo that is chemically contracepting animals, this could have big implications.”

Drea and her colleagues have identified more than 300 compounds in the scent secretions of female lemurs. “There is a rich communication system,” she said. Glands on the forelimbs, tail and other parts of the body secrete chemical cues that the lemurs rub onto branches or other community bulletin boards, where neighbors sniff out the news.

Working with 12 adult female ring-tailed lemurs at the Duke Lemur Center, Drea and her colleagues studied female genital odors by analyzing secretions chemically and observing animals’ sniffing behaviors. The researchers collected scents from females both before and after giving the animals a form of the hormone progestin called medroxyprogesterone acetate, or MPA, sold as Depo-Provera. Details of the study were published online July 28 in the Proceedings of the Royal Society B.

Female lemurs injected with MPA released a blend of scent components different from their normal odor, Drea reported. Some components disappeared, and others such as alcohols and fatty acids shrank in proportion.

Exactly what parts of an odor tell a lemur’s nose who’s who remain to be discovered. But researchers could no longer use scent to “fingerprint” an individual on birth control. “They smell like any other female lemur on contraceptives,” Drea said.

Lemurs use a sniff test to find out if a potential mate is a close relative and therefore an inbreeding risk. Yet smell differences among family groups degrade in the simplified scent of a female on contraceptives. “A female no longer smells like her brother,” Drea said.

Natural scents likewise contain information about how inbred an individual lemur is, Drea said. Contraceptives, though, made this signal harder to pick out of the noise.

The real experts — male lemurs — agreed that something was lacking from the scents of contracepted females. When males had a chance to sniff at wooden dowels marked with scents of the same female on or off contraceptives, males spent more time near the natural-odor dowel and sniffed and licked it intensely.