Researchers have found that African elephants have the largest number of olfactory receptor (OR) genes ever characterised – more than twice than that of dogs and five times more than humans.
The ability to distinguish different odours, which is important for sniffing out food, avoiding predators, and finding mates, depends on the number and type of olfactory receptors found in an organism’s genome.
“Apparently, an elephant’s nose is not only long but also superior,” said author Yoshihito Niimura from University of Tokyo in Japan.
Conversely, humans, along with our primate relatives, have much fewer numbers of OR genes compared to all other species examined, possibly as a result of our diminished reliance on smell as our visual acuity improved.
To characterise the olfactory capabilities of different mammals, the authors examined genome sequences from 13 placental mammals and identified over 10,000 OR genes in total.
The repertoire of OR genes found in any given species was highly unique – only 3 OR genes were shared and evolutionarily conserved amongst all 13 mammals.
Surprisingly, the African elephant had the most extensive olfactory repertoire, with almost 2,000 OR genes.
The study appeared in the journal Genome Research.