Ever seen a cat take a sniff of something and then look disgusted by it, with its mouth slightly open and perhaps its tongue sticking out? Or a horse with its front lip curled back and its upper teeth comically exposed?
In both cases, it’s a behaviour called the Flehmen response and it can be found in a wide variety of animal species.
What is the Flehmen response?
It occurs in response to a scent, and the aim is to expose the smell to the vomeronasal or Jacobson’s organ, which acts as a chemical receptor for moisture-bourne odours.
Located in the nasal cavity, this organ is found in mammals, amphibians and reptiles. Although it can be found in humans, it is not always present and it is thought to be vestigial and non-functional.
During the Flehman response – most often seen in felids and ungulates – the inhaled scent is directed to the vomeronasal organ and the animal actually stops breathing momentarily.
One of the main uses for this response is by males when sniffing a female’s urine, to assess her pheromones and learn whether she is in heat and ready to mate. While most species sniff the urine on the ground, it’s a long distance for giraffes, so males will nudge the female to encourage her to urinate directly into his mouth.
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