Why does My dog keep sniffing My bum

It seems gross. And it's embarrassing. But the gesture is a common (if poorly mannered) canine version of the "getting to know you" routine.

Dogs often greet one another by sniffing — which makes sense when your ability to smell is 10,000 times better than a human's. We all get that. But why does it have to be the butt, you ask?

Well, even the least smell-sensitive human can tell you that’s where a dog’s most intense aromas reside. In fact, there’s a pair of anal glands back there that secrete perhaps the most foul-smelling stuff you might occasionally have the displeasure to experience. So it’s perfectly normal.

Problem is, dogs often engage in this behavior enthusiastically, which can get them into trouble with other dogs who’d rather not have their butts smell tested. And, of course, it can also get them into trouble with humans who’d prefer that a dog not get so fresh with them. If your dog is an aggressive sniffer, it is something you can take up with a certified animal trainer or behaviorist.

Humans are often embarrassed when a dog trots over and starts sniffing at their groin, or pokes its snout in their butt. The dog has no idea that placing its nose in these parts of the human body might be offensive to some people, rather the dog is simply seeking information. The dominant sense for dogs is their sense of smell. Thus for canines reading scents is much like reading a written status report about the target of its sniffing. This is a common way to gather information from other dogs, and in many ways, dogs treat humans as if they were similar to canines.

A special kind of sweat gland called apocrine glands produces scents that convey social information. These chemicals are called pheromones. Dogs and most other mammals have their apocrine sweat glands spread over their entire body with higher concentrations in their genital and anal areas. The pheromone-releasing apocrine cells are even in the hair follicles, so a dog’s fur gets coated with these chemicals and concentrated for easier identification by other dogs. Bacteria begin to act on these secretions almost immediately, modifying and intensifying the smell. Pheromone scents not only identify the sex, age, health, and mood of the individual but also carry a lot of sexual information as well, such as where the female is in her estrus (menstrual) cycle, or if she is pregnant or having a false pregnancy.

Dogs even have a special scent detection system called Jacobson’s organ or the vomeronasal organ. It is a sort of pancake-shaped pouch of special receptive cells that is located just above the roof of the mouth. It has ducts that open to both the mouth and the nose to allow scent molecules to enter it. The large number of nerves and rich blood supply to this organ tells us that it is important to the dog, which is further verified by the fact that there is a special region in the olfactory bulbs in the dog's brain dedicated to processing the information from this special smell receptor.

In humans, the apocrine glands are found only in certain areas of the body, with the highest concentrations in the armpits and groin area so dogs try to sniff these areas for the same reasons that they sniff the genital regions of dogs. As when meeting other dogs, strangers receive the most attention of this sort, especially if there is a tinge of sexual scent. People who have had sexual intercourse recently seem to attract this kind of attention from dogs. Women who are menstruating or who have given birth recently (especially if they are still nursing their child) will also often find dogs impolitely sniffing at their genital region.

When a female ovulates, this also seems to cause a change in pheromones that attracts dogs. Some researchers noticed that the frequency of crotch sniffing went up dramatically around ovulation and decided to put this fact to use. They trained some Australian shepherd dogs to pick out cows that had just ovulated, allowing farmers and ranchers to successfully breed these cows during their short fertile period. The dog’s “sniff test” is considerably easier to administer and more reliable than most other methods of predicting ovulation. Perhaps this could open up a new class of assistance dogs for humans. Millions of women, who, for religious or cultural reasons use only the rhythm method of birth control, could be alerted by having specially trained dogs inform them when they are fertile. It would also give a new meaning to the familiar complaint of many husbands that their sex life “has gone to the dogs!”

Nonetheless, many people have strong negative reactions when a dog starts examining their body for scent messages. One instance where this negative reaction to crotch sniffing reached an extreme involved the case of Barbara Monsky, a local political activist living in Waterbury, Connecticut. Monsky’s reaction was so negative when she was sniffed by a dog that she brought a suit against its owner Judge Howard Moraghan and his Golden Retriever, Kodak. Specifically, she charged Moraghan with sexual harassment. Judge Moraghan often brought his dog to Dansbury Superior Court and according to Monsky, it was in the courthouse that the dog sexually harassed her when he "nuzzled, snooped or sniffed" beneath her skirt at least three times.

She based her charges on the contention that the judge was complicit in this harassment because he had done nothing about it. Fortunately for dog owners everywhere, when the case was finally brought before U.S. District Judge Gerard Goettel, he dismissed the case. In a later interview, he explained that “Impoliteness on the part of a dog does not constitute sexual harassment on the part of the owner.”

To read more about dogs’ noses and scent discrimination ability, click here or here.

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