Captive ring-tailed lemurs. The male produces a floral scent during the breeding season which has chemicals also found in coriander and cucumbers.Photograph: Baz Ratner/Reuters
‘Stink flirting’ observation may be first finding of primate sex pheromones, say scientists
An irresistible floral scent dabbed on the body may sound like a cliche from a perfume advert, but it appears to play a role in how male ring-tailed lemurs attract a mate.
Researchers in Japan say they have identified the odours males waft at females, and shown the latter’s attention is indeed captured by the pong.
They say these substances could be sex pheromones, chemical signals produced by all members of one sex within a species to affect the behaviour of the opposite sex, helping bag a partner.
If so, it would be the first time sex pheromones have been found in primates.
Kazushige Touhara, a professor and co-author of the research, at the University of Tokyo, said: “Male ring-tailed lemurs become more attractive to females by secreting a fruity and floral scent from their wrists’ glands in the breeding season.
“Using detailed chemical analysis we identified three compounds responsible for this scent, and this is the first time that pheromone candidates were identified in a primate.”
Male ring-tailed lemurs have scent glands on their wrists and shoulders which produce substances used to mark territory and threaten other males. But during breeding season males have also been seen to engage in “‘stink flirting” where they rub the liquid from their wrists on to their tails before waving them at females.
Writing in the journal Current Biology, Touhara and colleagues report that they collected samples of this liquid from the wrists of four captive male lemurs. They found that a greater volume and a more fruity, floral smell was produced during the breeding season, running from October to February. They also found females sniffed male scent marks for longer during the breeding season.
The team presented female lemurs with cotton pads bearing the liquid taken during the breeding and during non-breeding seasons; they found the females sniffed longer at the pads connected with the breeding period.
A chemical analysis revealed three chemicals in the liquid that increased during the breeding season. One of the chemicals is found in various fruits and vegetables and has a “green” smell, while another is found in coriander and cucumbers and smells floral, and the third, found in aged beef, smells like pears.
Among further experiments the team found signs that only a mixture of these was attractive to females – and only during breeding season – while boosting the testosterone levels of a male led to higher levels of one of the odour chemicals being produced.
“We think these pheromones are signals of male strength or dominance because the more testosterone is produced the more these odours are produced,” said Touhara.
While many animals, including mice, goats and all insects use pheromones, evidence for their use in primates, including humans, has proved elusive.
“Although there [is circumstantial evidence] that humans utilise olfactory cues for communication, there is no authentic pheromone that has been chemically identified,” said Touhara.
But, Touhara said that that did not mean scents were unimportant to humans. “There are probably crucial odours that affect each other’s emotions. For example, the baby’s head smell that parents sniff and feel happy [about]. Our research really encourages people, including us, to find olfactory cues that are utilised in humans.”
Tristram Wyatt, an expert in pheromones, at the University of Oxford, who was not involved in the study, said there was some evidence that humans might pick up on differences in scent between individuals. But, even if true, these would not be pheromones.
“That is quite different from the idea of molecules that are the same in every male or every female. The whole point is it is about differences,” Wyatt said. “Pheromones in humans are not ruled out, but the ones currently claimed are without evidence.”
He added that while the new study could spur on research into the matter, he agreed with the authors that it was too soon to say that sex pheromones had been found in primates. The results would need to hold in larger numbers of lemurs, and be shown to actually make a difference to the likelihood of mating. “It is good and exciting [research] but very preliminary,” he said.