Dogs sniff your crotch primarily because they rely on their powerful sense of smell to gather detailed information about people. The crotch area has a high concentration of apocrine sweat glands that release strong-smelling pheromones and body odors, which dogs use to detect information such as a person's age, sex, mood, and even recent activities like sexual intercourse or menstruation. This behavior is instinctual and used by dogs to "greet" others and gather biological and social information, similar to how dogs sniff each other's rear ends as a natural form of communication. Dogs have about 220 million scent receptors, far more than humans, making them highly sensitive to such odors. In summary, dogs sniff crotches because it gives them rich sensory clues about a person, rooted in their natural instincts and their exceptional olfactory abilities.
