flehmen

American  

[fley-muhn] / ˈfleɪ mən /

noun

1. Also called flehmen response.  Also called flehmen reaction.  a behavioral response of many mammals, especially deer and other artiodactyls, felines, and horses, consisting of raising the head and curling the upper lip to aid the sense of smell by increasing the flow of air through the nostrils and exposing the auxiliary olfactory organs: often a response to the detection of pheromones.

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verb (used without object)

1. (of deer, horses, and many other mammals) to raise the head and curl the upper lip to aid the sense of smell by increasing the flow of air through the nostrils and exposing the auxiliary olfactory organs.

Etymology

Origin of flehmen

From German Flehmen, noun use of infinitive: “(of a domestic ungulate) to curl the lip”; compare dialectal (Upper Saxony) flemmen “to look spiteful”; further relations unclear

Example Sentences

If cats smell something interesting, they will partially open their mouths and curl their upper lips, an expression called the Flehmen response.

From National Geographic

Anyway, to answer the question: A bighorn sheep that looks like it’s smiling probably isn’t saying “cheese” but sniffing pheromones and other scents in what’s called a flehmen response, said Harris.

From Washington Times

Next time you see your cat smell something and hold its mouth open with upper lips curled and teeth exposed in what is called the flehmen response, you can bet something tweaked its Jacobson’s organ.

From Slate

The vomeronasal organ detects hormones and other chemicals in urine with a characteristic intake of breath called the flehmen sniff.

From New York Times