Wildlife wednesday - flehmen response

By Andy Ames

If you have been watching the elk rut, undoubtedly you have seen this expression. What may look like a snarl or possibly a pucker is actually the flehmen response, meaning “to curl the upper lip” or “to bare the upper teeth.” In this case, the bull elk inhales with his nostrils closed and upper lip curled up in order to expose his vomeronasal organ (also known as Jacobson’s organ or VNO) located in his palate or roof of his mouth. The VNO functions as a secondary organ of smell. This organ has chemical receptors that allow animals to detect pheromones, useful in intra- or inter-species communication. These pheromones bipass the olfactory bulb of the brain to an accessory olfactory bulb with direct connections to regions of the brain that control sexual behavior and function — the amygdala and hypothalamus. Unlike Mule and Whitetail deer who alter their urinating stance when in heat, female elk show no visual indication that they are ready to mate. That is where the flehmen response comes into play. Periodically throughout the day dominant bull elk approach cow elk of his harem. He then smells her rear end or where she was laying, raises that upper lip, holds it for a couple of seconds, sometimes letting out a loud bugle, before moving on to the next cow. In this manner he is able to determine if she is in estrus or not. Since each female is only in estrus for a short period, it is important that the bull not miss his opportunity to mate.