The Flehmen response is where an animal curls back its upper lip exposing its front teeth and inhales for a long time. It happens when it encounters a new or distinctive smell. Or if it’s a smell they like. Or if it’s a scent they are trying to gather more information about.
This behavior facilitates the transfer of pheromones and other scents into the vomeronasal organ (also called the Jacobson’s organ) which are a pair of organs located above the roof of the mouth. Most amphibians, reptiles, and mammals have vomeronasal organs.
A pheromone is a chemical an organism produces which changes the behavior of another organism. Pheromones can tell others to get horny, get afraid, build a nest, etc. And pretty much all living organisms have them. Fish, bees, mammals, etc. Plants communicate by sharing pheromones! P.s. if you want to see a mindblowing video on the intelligence of plants here’s the link
If a mare is in estrus (that means she’s in heat) she will wink out some hormone and pheromone-scented pee and the male horse will be like Mmmm that’s captivating and exhibit Flehmen response so he can savor the pheromones. Then he will try to mate with her.
And get this- humans have vomeronasal organs too! Some folks argue that they are vestigial (meaning we have evolved to not need them) but frankly that is lot of baloney.
Here are the two vomeronasal organs in a human
People respond to each other’s pheromones. For example, they did a study where they had men smell women’s worn teeshirts. The ones they liked the best were the ones worn by women who were ovulating (peak sexy time for getting pregnant).
Pregnancy is technically only possible during the five days before ovulation through to the day of ovulation. These six days are the “fertile window” in a woman’s cycle, and reflect the lifespan of sperm (5 days) and the lifespan of the ovum (24 hours).
Men subconsciously respond to the pheromones telling him, this lady is ready to have your baby.
Pheromones also get detected by members of the same sex. It’s a well known fact that if a bunch of ladies live in the same house, they will often synchronize their periods, and all start menstruating at the same time each month. This is because they’ve been inhaling each other’s pheromones.
You can be subconsciously aware of another person’s emotional and physical states such as fear, sexual arousal, and quality of health simply by sniffin’ their pheromones. It’s a good thing!