 Cats have an acute sense of smell , due in part to their well @-@ developed olfactory bulb and a large surface of olfactory mucosa , about 5 @.@ 8 cm2 ( 0 @.@ 90 in2 ) in area , which is about twice that of humans . Cats are sensitive to pheromones such as 3 @-@ mercapto @-@ 3 @-@ methylbutan @-@ 1 @-@ ol , which they use to communicate through urine spraying and marking with scent glands . Many cats also respond strongly to plants that contain nepetalactone , especially catnip , as they can detect that substance at less than one part per billion . About 70 — 80 % of cats are affected by nepetalactone . This response is also produced by other plants , such as silver vine ( Actinidia polygama ) and the herb valerian ; it may be caused by the smell of these plants mimicking a pheromone and stimulating cats ' social or sexual behaviors . 
