When two dogs meet, they invariably give one another’s private parts a good sniff. This will happen almost always, even on second meetings. It is only when one dog is averse to being sniffed that this ritual goes unobserved, as the unwilling participant will use body language and growling to warn the other dog away from approaching. In most cases, the ritual is consensual and once complete, the two dogs will typically move on to other interactions, such as play.
They Can't Help It
Sniffing is an instinctive behavior and dogs are programmed to sniff each other when they meet. Dogs get more information about their environment via scent than they do via sound or sight. Going in for a sniff of another dog’s private parts is not a conscious decision; dogs are always attracted to the strongest scented substance or item in their immediate environment. Unless there’s a plate of freshly cooked beef on the floor, it’s most probable that a dog’s immediate interest lies at the back end of the other dog, in his anal glands, to be precise.
Nice to Meet You
Sniffing forms part of the larger greeting ritual that occurs between two dogs. The behavior invariably occurs when they meet. It is highly unlikely that two dogs will engage in sniffing after having been in one another’s company for some time, unless one of the dogs has been to the toilet and has created a new set of scents for sniffing. Other greeting habits include posturing, play bowing and occasional barking and snarling.
Tell Me About Yourself
The private areas of a dog contain a wealth of information. From one sniff of a dog’s anal gland, the other dog can tell gender, approximate age, pack status (dominant dogs give off different pheromones) and even whether the dog is in season. All of this information enables each dog to make judgements and decisions about how to progress the relationship. For example, if a male dog smells that a bitch is in season, he may try to mount her.
Me First, I'm Top Dog
The dominant dog typically takes the initiative and sniffs the other dog. In cases where a highly dominant dog meets a highly submissive dog, the submissive dog may automatically roll over to allow himself to be sniffed. In cases where the social order between two dogs is yet to be established, they both may attempt to sniff first, at which point it becomes a battle of wills.