Ring-tailed lemurs sniff out weakness
Sophisticated scent ‘ bouquets’ communicate information on the health of rivals.
The smell of success may be sweet, but the whiff of weakness is apparently pungent. New research shows that ringtailed lemurs can tell whether a rival is injured just by sniffing its scent marks.
Ring-tailed lemurs mark territories and signal their social status to others using a sticky aromatic cocktail of hundreds of different molecules, which they plaster on vegetation. “I couldn’t say the female odour, which is the strongest, is particularly pleasant, but the males sure seem to like it,” says Christine Drea of Duke University, USA, who led the work.
But the data collected by Drea and her team is revealing a level of sophistication to the information contained in these “chemically elaborate bouquets” that is not to be sniffed at. For their latest study, the biologists compared the scent signatures of healthy adult lemurs with those of 23 animals that had sustained injuries, mostly during fights with rivals. While their wounds were healing, these animals’ scents contained significantly fewer chemical components than normal. Once they’d recovered, though, they regained the full complement of compounds.
What’s more, other lemurs were able to detect these changes and respond accordingly – rivals were more likely to over-mark an injured animal’s scent with their own.
“They respond more competitively when they could easily have the upper hand,” says Drea.
It may be that, like gaudy plumage or impressive antlers, these chemical signals are costly to manufacture. While a healthy animal is able to make the necessary investment, an injured lemur must channel its resources into the healing process and its immune system. Indeed, the effect was especially strong during the breeding season, the most stressful and demanding time of year for the primates.
For the injured animal, signalling its weakened condition through the medium of scent might have other benefits, by allowing it to avoid risky physical encounters with fitter, stronger opponents.
Intriguingly, the scent profiles of injured animals were changed further in those individuals that were treated by vets with antibiotics. The biologists are now working on the theory that the scent compounds are manufactured by symbiotic microbes living in the lemurs’ guts that help their hosts digest foliage. SB