Washington, June 24 : For humans, perfumes and colognes may all have to do with superficiality, but when it comes to the world of primates, scents go much deeper.
According to a new research that looked into hundreds of chemical components in a ringtailed lemur's distinctive scent, the male species use their distinctive scent not just for advertising their fitness for fatherhood, but also to reflect his mixture of genes.
Ringtailed males have scent glands on their genitals, shoulders and wrists, each of which makes different scents. Other lemur species also have glands on their heads, chests and hands. Add to these scents the signals that can be conveyed in feces and urine, and there's a lot of silent, cryptic communication going on in lemur society.
"We now know that there's information about genetic quality and relatedness in scent," said Christine Drea, a Duke associate professor of biological anthropology and biology.
"It's an honest indicator of individual quality that both sexes can recognize," she said.
Lemurs, distant primate cousins of ours who split from the family tree before the monkeys and apes parted ways, have a complex and elaborate scent language that until recently was completely undiscovered by humans.
"All lemurs make use of scent. The diversity of glands is just amazing," Drea said.
Wearing a scent-based nametag declaring one's genetics is probably useful in avoiding aggression with closely related males, Drea said.
It's also quite likely to help prevent inbreeding by signaling family relationships to females, but the research to prove that is still ongoing, she added.
In the study, Drea and colleagues focused solely on male ringtailed lemurs living at the Duke Lemur Center.
The males have a gland and spike on each wrist that is used to scratch and mark saplings with highly aromatic scents. A pair of glands on the shoulders "like misplaced nipples" manufacture squalene, a scent molecule that works like glue to keep the more aromatic compounds in place longer.
Males can be seen dabbing the wrist gland on the chest gland and then scratch marking. The wrist glands are also central to the "stink fighting" of ringtails, in which they rub the glands along the length of their bushy tails, and then foist them into each others' face to express dominance.
Most importantly, the male also has a scent gland on his scrotum that becomes critical to marking territory and advertising fitness during mating season. He does a handstand and rubs this gland directly onto a tree trunk to let any interested lemurs know who he is and what he's made of.
Scent not only speaks volumes, it's physiologically expensive to make, Drea said.
When a lemur is ill or socially stressed, its scent changes dramatically.
"If he loses his signals, it's quite likely its because he's less genetically fit. And his sexual or social partners can know that," Drea said.
Female ringtailed lemurs have just one scent gland in the genital area, but their scent is more complex than the males'. Via scent, females may advertise not only their fertility, but the presence of a pregnancy and how far along it is, Drea said.
The study "Smelling Right: The scent of male lemurs advertises genetic quality and relatedness," appears online in the journal Molecular Ecology.