Dogs sniff our genitals in order to get to know us. Like dogs, human genitals and anuses are loaded with apocrine glands that produce pheromones containing information on age, health, mood, sex, and reproductive status. Armpits also contain apocrine glands, but dogs tend to choose the crotch because it’s already at roughly nose height.
The Jacobson's Organ
The Jacobson’s organ, or vomeronasal organ, sits at the roof of the mouth behind the incisors. It handles the detection of pheromones, which are used for social and sexual communication.
Have you ever seen your dog’s upper lip retract and their teeth chatter, especially after smelling urine? Known as the Flehmen response, this movement redirects a chemical odor to the Jacobson’s organ for analysis.
Dogs have a larger vomeronasal organ than other mammals of similar size and weight, but a shorter vomeronasal duct. The larger organ size is believed to be responsible for increased sniffing behavior in canines, while the shorter duct reduces the loss of scent particles as they move towards the organ.
Why dogs greet strangers by sniffing
Dogs are the journalists of the domesticated world. Every inhale brings a wealth of information to their nose. Air is even expelled out the side slits so as not to interfere with the constant stream of data rushing in.
An introduction between dogs resembles less a handshake and more a Wikipedia article. Upon greeting an unfamiliar dog, polite dogs circle each other and sniff each other’s butts before they progress up to the face. As a bonus, this keeps each other’s sensitive noses and eyes away from each other’s faces until they’re sure of the reception.
When dogs approach humans, they’re extending us the courtesy of a polite greeting in their own language. On our end, we try to meet them halfway by extending a hand to sniff–however, shy or nervous dogs can be startled by what appears to be a stranger making direct eye contact and reaching for them. Not to mention, their sense of smell is good enough to smell our hands from several feet away. If you want to greet a dog, let them sniff their fill before making a move to interact!
When a dog smells our pheromones, they detect changes caused by pregnancy, birth, ovulation, breastfeeding, menstruation, and recent sexual activity. Catching a whiff of this from a distance can trigger curiosity and make a dog more likely to approach.
In case you were wondering, feel free to keep your nose out of your dog’s butt. They won’t be offended!