An elephant's nose knows the secrets

We’ve long known that African elephants have a great sense of smell but a new study shows that the large mammals have a truly superior schnozzle, writes Christine Dell’amore.

Compared with 13 other mammal species studied, African elephants have the most genes related to smell: 2,000.

That’s the most ever discovered in an animal – more than twice the number of olfactory genes in domestic dogs and five times more than in humans, who have about 400, according to research published in the journal Genome Research. The previous record-holder were rats, which have about 1,200 genes dedicated to smell.
Why so many? “We don’t know the real reason,” study leader Yoshihito Niimura, a molecular evolutionist at the University of Tokyo, said by email.

But it’s likely related to the importance of smell to the poorly sighted African elephant in interpreting and navigating its environment.

For instance, smell is a crucial sense for the functioning of an elephant trunk, which acts like a hand as it grips food and other objects.

“They use olfaction to quest the outer world, which may drive (their) superior sense of smell,” Niimura said. “Imagine the situation (in which) we have a nose on our palm!”


Sniffing genes

The team wanted to discern smell-related genes for as many species as possible, but very accurate genome information is available for only 13 mammal species, he said.
The team ran a special computer program that identified the elephant’s 2,000 olfactory genes. In doing so, they also wanted to get a better understanding of the function of these genes.

Their analysis revealed that over the course of evolution, one ancient gene dedicated to smell has created as many as 84 additional genes that the animals likely use to detect odours specific to their environment – for instance, the smell of certain foods on the savanna.

“On the other hand, some other genes are evolutionarily very stable, without any change in number and with very few changes in sequence. These genes (are likely) very important for the survival of any mammal,” said Niimura.

He also emphasised that research on olfactory genes is still limited, and that another species – say, the Asian elephant could very well break the African elephant’s record.

Superior smellers

Overall, though, his research supports behavioural studies that show African elephants have an incredible nose for detecting odours. For instance, studies have revealed that African elephants can distinguish between the scents of two ethnic groups in Kenya: the Maasai and the Kamba.

“Maasai men spear elephants to show their virility, while Kamba people are agricultural and give little threat to them; therefore, elephants are afraid of Maasai men,” he said.

Joyce Poole, co-founder of the conservation group Elephant Voices, also referenced this ability of elephants to distinguish between tribes. “This is a fascinating study that confirms what we have observed in the field,” Poole, also a National Geographic explorer, said by email.

“If the wind is blowing in the correct direction, elephants can pick up the scent of humans from over a kilometer [0.6 mile] away or detect and find the exact location of a tiny sliver of banana from over 50 meters [160 feet] away,” she said.

In addition, “experimental studies show that by sniffing urine-soaked soil, elephants can discriminate between and keep track of the location of family members.”
“Want to know what is going through the mind of an elephant? I have always said: Watch the tip of its trunk.”