“It’s like having a nose on the palm of your hand,” says Professor Yoshito Niimura.
And what a nose! Considering the size of an elephant’s shnoz, it’s no surprise that they have an enhanced sense of smell compared to humans.
But Dr Niimura and his colleagues have just figured out how much more complex it really is. Pachyderms have five times as many olfactory receptor genes as people do.
Dr Niimura, who is based at the University of Tokyo, and his team revealed in Genome Research that Loxodonta africana have almost 2,000 olfactory genes compared to less than 400 in Homo sapiens.
The number of genes doesn’t guarantee greater sensitivity, though. No one is suggesting, for example, that bloodhounds (dogs have around 1,000 olfactory receptor genes) be replaced by elephants.
“Dogs are very good at smelling particular odors,” Dr Niimura said, “like the smell of humans. They can detect those odor molecules even at very low concentrations. In that sense, a dog has a sense of smell that’s something like a million times better than a human’s.”
Elephants, by contrast, likely have a broader range of identifiable smells. An earlier study in Chemical Senses showed that Asian elephants could distinguish between similar molecules that humans would treat as the same.
Elephants can even recognise individuals of their own species by subtle differences in the fragrance of their urine.
And African elephants can tell which tribe a human comes from by smell, according to a 2007 study reported in Scientific American. In Kenya, some were able to distinguish the smell of young men from the Maasi tribe, who hunt elephants, and that of youths from the Kamab tribe, an agricultural people who don’t.
“The functions of these genes are not well known, but they are likely important for the living environment of African elephants,” said Dr Yoshito Niimura, who led the research, published in Genome Research.
All mammals, and most other animals, use smell to find food, warn of predators, and seek mates.
“The large repertoire of elephant genes might be attributed to their heavy reliance on scent in various contexts, including foraging, social communication and reproduction,’ Dr Niimura said.
They use their trunks to interact with the world, he noted. Imagine if, “every time you touch something, you smell it”.
Elephants had more than 50 per cent more smelling genes than their closest rivals in the study, rats, which have just 1,200. Cows came a close third.
Surprisingly, several other primates have even worse smell than humans. Marmosets have just 366 olfactory genes, macaques 309 and orang-utan’s 296.
The scientists also traced the growth of groups of olfactory receptor genes, noting their duplication or loss in each species.
