Elephants are known for their impressively long trunks, but perhaps less well known is the large number of genes that code for their sense of smell.
In a study of 13 mammals, African elephants were found to be superior sniffers, possessing the largest number of genes associated with smell — five times as many as humans and more than twice that of dogs.
The findings support other research on the pachyderm's superior sense of smell. African elephants can smell the difference between two tribes living in Kenya: the Maasai, whose young men prove their virility by spearing elephants, and the Kamba, farmers who usually leave elephants alone. That finding was reported in a 2007 study published by the journal Current Biology.
Elephants also use their sensitive sense of smell to forage for food and identify family members. Female African elephants are able to reproduce for only a few days every three years, and research suggests that males can smell when a female is receptive to reproduction, said Bruce Schulte, head of the department of biology at Western Kentucky University in Bowling Green.
In the latest study, researchers looked at the number of olfactory receptor genes in each mammal. These genes code proteins that reside in the nasal cavity and bind to odor molecules. Nerve cells then relay the information to the brain, which classifies the smell.
The number of olfactory receptor genes ranged from 296 in orangutans to 1,948 in African elephants, the researchers found. An analysis showed that the common ancestor of all 13 mammals had 781 such genes. This indicates that the number of olfactory receptor genes has increased over time in elephants and rodents, while it has decreased in primates — including humans, who have 396 such receptor genes.
The study was published Tuesday in the journal Genome Research.