Nature's cologne

Lemur study finds first evidence of a human-like mating trait

They call it "stink flirting."

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Spring is in the air and that means one thing for ring-tailed lemurs: It’s time to get busy.

For these bright-eyed primates, mating is concentrated during a few weeks each April — and now, researchers know exactly how their unique biology helps male lemurs spit their game.

In a new study, scientists identify three specific chemicals that make up the strongly scented pheromones male ring-tailed lemurs produce to attract a mate: A ritual scientists call “stink flirting.”

The intricate chemical analysis marks the first time scientists have been able to identify sex pheromones in a primate, say the researchers behind the new study.

Using gas chromatography and mass spectrometry, the scientists analyzed secretions coming from male lemurs' wrist glands. The three organic chemical compounds that endow each lemur with its particular biological cologne are aldehydes. These molecules are found in perfumes, plants, and in humans.

Interestingly, researchers believe the same three chemicals are at play in how ewes recognize their newborn lambs. And one of the chemicals, called tetradecanal, is a known sex pheromone found in some species of insects.

In lemurs, when mating season is underway, these chemicals start ramping up production significantly, the researchers found.

The special, three-part blend of mating season pheromones is effective at capturing female lemurs’ attention, the researchers found — but only when all three are in the mix. By presenting female lemurs with different mixtures of the aldehydes at different times of years, the works answers some standing questions about how lemur love really works.

The research was published on Thursday in the journal Current Biology.

A male lemur shows his inner-wrists, where special glands secrete pheromones used to get the attention of lady lemurs.Chigusa Tanaka, Japan Monkey Center

Stink flirting, explained

Male ring-tailed lemurs, or Lemur catta, produce the sex pheromones from glands in their wrists. Then, as if it were nature’s cologne, they dab their wrists on their bushy tails, scenting them, before waving them around to advertise their mating prowess to females.

The fruity-smelling chemicals help male lemurs make the case for why a female should choose them. A certain aroma may indicate that a male lemur is able to fight off disease and parasites, for instance, suggesting his genes would be worth passing down to offspring.

You can see it all go down in this BBC Earth video:

Seasons of love

For the new study, researchers studied lemurs at the Japanese Monkey Center to see how the chemical compounds affected female lemurs’ behavior.

It seems these pheromones have some seasonality. The researchers isolated pheromones from males during the mating season and during the off-season, and presented both to females. Females sniffed at the sweetly seasonal, fruity fragrance for twice as long as they did the bitter-smelling, out-of-season odors. At the same time, the females sniffed at pheromone markings for a longer amount of time during breeding season — the same time they’re looking to take a mate.

How much of the pheromones a male lemur produces changes throughout his life. Younger (but sexually mature) males make more of the chemicals than seniors, a trait that may be linked to the amount of testosterone they produce at each age. The potency of the chemicals also decreases over time — females seem less impressed by the sex pheromones of the older male lemurs.

The new research also confirms that these three chemicals are pheromones. Future research will determine whether or not they directly affect sexual behavior — the stuff that happens after the sniff, in other words.

That’s important, because lemur love can be pretty nuanced. There can be mere seconds of difference in the smelling (or licking) behavior females exhibit to show that they are interested in the pheromones, the researchers say.

But it seems to be just enough time for a female lemur to show a male that she’s picking up what he’s putting down.

Abstract: Among rodents, information about the external world is mainly acquired via the olfactory system, which is one of five sensory modalities. Several semiochemical signals are used for inter- and intraspecies communication [1]. In contrast, primates are generally regarded as vision-oriented mammals, and have been thought to trade their olfactory sensitivity for good sight. However, strepsirrhines have a well-developed olfactory system [2] and a larger repertoire of functional olfactory and vomeronasal receptor genes than haplorhines [3, 4]. Moreover, strepsirrhines are well known for their use of olfactory communication in social behavior. Ring-tailed lemurs are a species of Malagasy strepsirrhines, and use olfactory cues for conspecific communication. Male lemurs mark their scent by spreading volatiles from the antebrachial gland on their wrists. This study combined ethological and chemical approaches to identify a key odorant(s) in antebrachial secretions involved in the sexual communication of lemurs. The results of a behavioral assay indicated that females sniff the males’ antebrachial secretions longer during the breeding season than during the nonbreeding season. By examining seasonal changes in volatiles using gas chromatographymass spectrometry, we found that the secretion of three C12 and C14 aldehydes with a fruity and floral scent significantly increased during the breeding season in a testosterone-dependent manner. Females sniffed for longer at biologically relevant concentrations of two of the aldehydes (12-methyltridecanal and tetradecanal) and were attracted to a mixture of these plus the third aldehyde, dodecanal. Our results suggest that these aldehydes are putative lemur pheromones involved in the attractiveness of males to females during the breeding season.
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