LEMURS CAN SMELL WEAKNESS, NEW STUDY SHOWS.
Researchers see an evolutionary advantage
While many animals are known to ruthlessly purge weakness from within their midst, a new study has found that lemurs have the unique ability to detect the weak by smell alone.
Specifically, a ring-tailed lemur can spot an injured compatriot purely by the odours wafting from their genitals.
“Our study shows that physical injury from peers dampens an animal’s scent signature, and in a way that its counterparts can detect,” Duke University researcher Christine Drea said in a statement accompanying the new study.
The consequences for an injured lemur — particularly a male lemur — are catastrophic. For an injured male literally reeking of vulnerability, they will quickly find females refusing to mate with them and males targeting them for attack.
Lemurs “respond more competitively when they could easily have the upper hand,” said Drea.
Lemurs are tree-dwelling primates that live in small, “aggressively female-dominant” groups according to the study, published last week on Nature.com.
The animals also rely heavily on foul-smelling body odour.
Similar to the territorial spraying of a male house cat, lemurs of both sexes routinely mark their territory with musky genital secretions rubbed on twigs, branches and the like.
But if a lemur becomes injured, the study found that they can no longer generate the chemical cocktail needed to create a healthy, full-bodied musk.
The study based its findings on a library of genital secretion samples collected from 23 lemurs held in captivity at the Duke Lemur Center, a North Carolina facility that holds the largest collection of lemurs outside the animals’ native Madagascar.
Researchers also dutifully watched their lemurs to document “naturally occurring” injuries sustained by the animals.
Thirty-four “unique injury events” were documented by the study, the vast majority of them occurring in fights. One injury, for instance, saw a male lemur walk away from a brawl with pulled hair, a cut under his left eye and a deep gash in his hand.
Scientists analyzed the lemurs’ genital secretions using gas chromatography and determined that there were noticeable chemical differences between the secretions of injured and uninjured lemurs.
An injured lemur’s secretions had reduced “chemical complexity” that the other lemurs seemed able to detect.
When male lemurs were presented with a wooden rod smeared with the secretions of an injured compatriot, they were much more likely to smear the rod with their own stench — an aggressive act akin to kicking sand into the face of a romantic rival.
Although harsh, researchers believe it is an evolutionary advantage that lemurs are physically unable to conceal weakness. Female lemurs are less likely to be duped into mating with a weaker partner, and male lemurs are better able to pick fights that they know they can win.
“Honesty is crucial in animal communication when signallers are conveying information about their condition,” read the study.
It’s not a particularly new discovery that animals will use smell to assess the condition of a compatriot. For instance, many animals have been documented as having the ability to smell sickness. There have also been prior studies showing that lab rats will exude measurably different odours if injured.
Nevertheless, the Duke University authors claim this is the first time in scientific history that a wounded animal has been seen to lose its social standing due purely to smell.
Or, as the study put it, “the first supporting evidence for a socially relevant olfactory indicator of naturally occurring injury.”