Is It Possible to Smell Weakness? Lemurs Can.

An injured ring-tailed lemur’s personal scent plummets, and others can use that as a signal to swoop in on mates or territory.

You can’t bluff a lemur.

Humans can put on their “game face” to appear tough, but ring-tailed lemurs use scent to size up their opponents. That means these small cat-size primates from Madagascar can’t fool each other just by looking strong—they have to smell strong too.

How do they literally smell weakness on potential rivals?

Male and female ringtails have scent glands in their genital areas, while males also have them in their wrists and shoulders, all producing different scents. This personal eau de ring-tail says lot about a lemur’s health. (Related: People are also surprisingly good at smelling when someone’s sick.)

A decade-long study from Duke University’s Lemur Centre has found that ring-tailed lemurs who sustain an injury temporarily scale back on their signature body odour, which is costly to produce. The loss creates a deficiency other lemurs can smell and exploit, researchers reported in June in the journal Scientific Reports.

Lemurs live in social groups called troops that are led by a dominant female, but “both males and females use aggression and scent marking to maintain their social status,” says lead author Rachel Harris, a behavioural and chemical ecologist doing postdoctoral research at the Duke Lemur Centre at the time of the study.

And lemurs are tough cookies. 

GIRL POWER In ring tailed lemur society, the ladies rule the bunch!

“The females are dominant and aggressive,” says Christine Drea, an evolutionary anthropologist at Duke. Males fight each other, females fight one another for control, and females fight males “because they can. They’re pissy little gals,” Drea says. (See how lemurs rank in aggression in “How Human Violence Stacks Up Against Other Killer Animals.”)

These pugilistic primates suffer injuries from fights and accidents in captivity and in the wild.

The recent study analysed genital secretions of 23 lemurs at the centre who were injured, mostly in fights, and compared their scents before injury and while they were injured and after healing.

Once injured, “their entire olfactory signature kind of flat-lined or disappeared,” Drea says.

Injured lemurs lost up to 10 percent of their scent, experiencing an overall dampening as well as losing whole compounds from the hundreds that compose their odour.

And in lemur land, body odour, or rather the lack of it, really impedes your social life.

The Price of Perfume

Lemur status is reflected by both the quality and quantity of the scent, Drea says. So to stay ahead of the competition, a lemur will mark trees and branches on its own and also mark over the scents that other lemurs have left behind.

Males who detected a weak odour signal were more likely to place their own scent on a spot previously marked by an injured lemur than one marked by a healthy one. This suggests the over marking male sees the male with the lighter scent as a weaker competitor. That injured male would also have a diminished ability to go out and mark again.

RAISING CUTE BABY LEMURS TO SAVE A SPECIES - Lemur babies stay close to mom for the first months of their lives. Endangered lemurs in this video are watched closely at the Duke Lemur Centre in North Carolina, which has the world's largest collection of lemurs outside of Madagascar. Video.

Diminished scent in wild or captive male lemurs “could have serious consequences for that animal’s social standing within the group,” Harris says. “Injured animals may lose their high-ranking social status, or lose breeding access to potential mates.”

The results suggest the same behaviour could be happening in females, though there isn’t enough data to be sure. Females are, however, just as invested in scent as males.

“There can be over 300 different scent components in a female’s scent mark, compared with a male’s 200 or so scent components,” Harris says. Females closely investigate scent marks, she says—likely to assess rivals, “especially other females.”

The study also confirms that these unique scents take a lot of energy to produce, as evidenced by injured animals having to scale back on them while they heal.

“Only a strong, robust animal can pay that cost,” Drea says.

LEAD IMAGE: When a male ring-tailed lemur like this one has been injured, he becomes vulnerable to losing his social status. PHOTOGRAPH BY CYRIL RUOSO, MINDEN PICTURES/ NATIONAL GEOGRAPHIC CREATIVE

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