Flehmen Response

A Red Deer Stag (Cervus elaphus) emerges from the bracken during the rut with a strange sneering expression and a crazy look in its eye at Richmond Park, London. Stretching its neck, lifting its nose in the air and curling its top lip it is maximising the exposure of its vomeronasal organ, located in the roof of its mouth, to air containing pheromones and other scents. At this time of the year it is most interested in detecting an estrous doe. This triggers the stag’s reproductive instincts to go on high alert in preparation for opportunities to breed. This behaviour is known as the Flehmen Response originating from the German verb Flehmen meaning “to curl the lip.”