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Elephant genome contains almost 2000 olfactory receptor genes. Reuters

Bomb detection squads may switch from dogs to elephants going by a recent study by Japanese scientists that proclaims the pachyderm as the species with a strongest sense of smell.

Just like the trunk that is long, the African elephant's genome contains a long chain of olfactory receptor genes, nearly 2,000, says the study in the journal Genome Research.

This means elephants' sniffers are five times more powerful than human noses, twice that of dogs, and even stronger than the previous known record-holder in the animal kingdom: rats.

Just how these genes work is not well understood, but they likely helped elephants survive and navigate their environment over the ages. The ability to smell allows creatures to find mates and food and avoid predators.

The other unexplained point is whether a big number of genes translates into any significance in the light of the recent findings that a major section of the human DNA is simply junk.

The study compared elephant olfactory receptor genes to those of 13 other animals, including horses, rabbits, guinea pigs, cows, rodents and chimpanzees.

Primates and humans actually had very low numbers of genes compared to other species, the study found.

This could be "a result of our diminished reliance on smell as our vision improved," one of the scientists said.

The research was funded by the Japan Science and Technology Agency and the Japan Society for the Promotion of Science Grants-in-Aid programme.