2021—The Flehmen Response

Animal behavior is fascinating. One of the behaviors that Rocky Mountain Bighorn rams exhibit is curling back their upper lip to expose their teeth, inhaling with nostrils closed, holding their head high, and staying still for several seconds. Bighorns have a gland in their mouths that can sense pheromones. I have witnessed this behavior when ewes are nearby and I have been told it is the way rams determine if a ewe is in estrus. This behavior is not limited to sheep. It is common behavior in lots of ungulates and even other kinds of mammals including big cats. And, it has a name. It is called the flehmen response and sometimes, the flehmen grimace. Flehmen is a German verb that means to bare the upper teeth and that word is derived from a Saxon-German word that means to grimace. The term for this behavior was coined in the 1930’s by a zoo keeper in Germany who observed the behavior in many different zoo mammals. There is apparently no English equivalent for this behavior so flehmen it is. It doesn’t really look like a grimace to me. The rams look more euphoric or enraptured than grimacing.