Maybe the saying is actually that an elephant never forgets a smell.

Elephants have an impressive 2,000 olfactory receptor genes, twice as many as dogs have and five times as many as humans, The Washington Post reported. Researchers studied 13 mammal species to find that African elephants topped the list when it came to genes related to smell, publishing their findings today in Genome Research.

"The functions of these genes are not well known, but they are likely important for the living environment of African elephants," study author Yoshihito Niimura said in a press release. "Apparently, an elephant's nose is not only long but also superior." 

So do elephants smell things more keenly than humans or dogs do?

Scientists say there isn't necessarily a clear link between the number of olfactory genes in a species and a highly developed sense of smell.

"We don't really know how the number of olfactory receptor genes relates to olfactory ability," said study author Yoshihito Niimura, a researcher at the University of Tokyo's department of applied biological chemistry, as quoted by the Post. "For example, dogs are known for their keen sense of smell--but we actually already knew that their number of genes was much smaller than mice, who we don't see with that same ability." 

Smell is an especially important sense for elephants since they use it to navigate their environment, National Geographic reported. While scientists aren't certain how their olfactory senses compare to a dog's, elephants can keep different elephant groups distinct by smelling them, according to earlier behavioral studies.

"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," said Joyce Poole, co-founder of the conservation group ElephantVoices, as quoted by National Geographic. "Experimental studies show that by sniffing urine-soaked soil, elephants can discriminate between and keep track of the location of family members."

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