Sense of smell is critical for survival in many mammals. The ability to distinguish different odors, which is important for sniffing out food, avoiding predators, and finding mates, depends on the number and type olfactory receptors found in an organism’s genome. In a study published today in Genome Research, researchers examined the olfactory receptor (OR) repertoire encoded in 13 mammalian species and found that African elephants have the largest number of OR genes ever characterized; more than twice that found in dogs, and five times more than in humans.