Name for Upper Lip Curling Behaviour in Bull

The curling of the upper lip and sniffing behaviour shown by the bull is known as:

Correct Answer: Flehman's reaction

The characteristic behaviour of a bull curling its upper lip (lip curling/retraction) while sniffing the urine or vaginal secretions of a cow is called Flehman's reaction (also spelled Flehmen response). This behaviour facilitates the transport of pheromones and olfactory chemicals to the vomeronasal organ (Jacobson's organ) for evaluation of the female's reproductive status.

Flehman's Reaction Details

• Seen in: Bulls, stallions, rams, cats, horses, and many other mammals
• Purpose: Olfactory evaluation of estrogen/pheromone content in female urine/secretions to determine if she is in heat
• Mechanism: Upper lip is curled back → nostril is closed → air/volatiles are channeled to the vomeronasal organ (VNO) in the nasal septum

Ferguson's Reflex vs. Flehman's Reaction

• Ferguson's reflex: Oxytocin-mediated positive feedback during parturition and suckling
• Flehman's reaction: Olfactory sexual behaviour for estrus detection