Flehming response: Definition: is a behaviour whereby an animal curls back its upper lips exposing its front teeth, inhales with the nostrils usually closed and then often holds this position for several seconds. It may be performed over a site or substance of particular interest to the animal (e.g. urine or faeces) or may be performed with the neck stretched and the head held high in the air. Flehmen is performed by a wide range of mammals including ungulates and felids. The behaviour facilitates the transfer of pheromones and other scents into the vomeronasal organ located above the roof of the mouth via a duct which exits just behind the front teeth of the animal.
Bull bison flehming….
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Dancing Aspens Farm Blog 
Well I never heard that term before. Thanks for explaining it. These shots are brilliant.
Fascinating!
Hello Erin… I see our cats do this from time to time, but didn’t know the term… I am not making an announcement yet, but my only child, my daughter will be having a baby in April. It was a tough first trimester and we hope all goes well…. I think of you and the wonderful Mom you are. I know my kid will be a good Mom…hugs…Michelle
Now, that would scare me just a bit!
Fantastic shots of the bison exhibiting this behavior. Now, when I see my cats do this I know what to call it!