Lemur Couples Use Scent to Declare Partnership

For coupling lemurs, the smell of love is not just in the air, it's in their scent.

The latest study from the Duke Lemur Center in Durham, N.C. has revealed that the strength of a lemur couple's bond is reflected in the similarity of their scent, which they secrete from glands that produce a sticky goo that is blotted on tree branches and elsewhere to mark territory.

The reason for this scent-pairing is unclear, but researchers speculate that it could be a way to combine territory defenses or to advertise relationship status to the rest of the group.

Additionally, lemurs spend significant time scent-marking and investigating one another's scent before having babies, and once they reproduce they smell more like each other and their offspring give off similar scents to their parents.

For the study, which is published it the journal Animal Behavior, Lydia Greene, a research associate in Duke's evolutionary anthropology department, and her adviser Christine Drea observed six pairs of potential mate. The lemurs in the study were Coquerel's sifakas, white-furred lemurs with chocolate-brown patches on their chests, arms and legs. Green and Drea measured how often the lemurs smeared their scented goo - which contains in excess of 250 odor compounds - on their surroundings. They also observed how often the lemurs sniffed, licked or marked over the scents left by other lemurs in the group.

They observed that lemur partners mirrored each other's scent-marking behavior.

"When one member of a pair started sniffing and scent-marking more often, their mate did too," Greene said, adding that this time the lemurs spend devoted to one another's scent may be a sort of "getting-to-know-you" period.

"If two animals have never reproduced, the male doesn't necessarily know what the female smells like when she's in heat, because they've never gone through this before. They might need to scent mark a lot more to figure out when it's time to mate," Greene said.

The number of years a lemur couple had been together did not appear to make a difference in the similarity of their scents, the researchers found.

"Some of the sifaka couples had been living together for quite a while, but hadn't managed to produce an infant, whereas others had been living together for a really short period of time and had already successfully reproduced," Greene said, noting that couples with kids had more similar odor profiles, likely due to the frequent exchange of body fluids that comes with grooming, mating and other physical contact.

The scent similarities could be the social equivalent of a wedding ring.

"It could be a signal that they're a united front," Drea said.

"[They could be saying] we're a thing. We've bonded. Don't mess with us," Greene added.