Why do dogs sniff other dogs bottoms?

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Little dog sniffing big dog's buttOf course you’ve seen it – dogs sniffing the butts of other dogs. So, why do dogs sniff other dogs bottoms? Come on, be honest. I know you’ve always wanted to know!

I’ve often thought “What if humans sniffed each other’s butts?” Have you ever wondered? (I fear I may be the only one who has).

Anyway, it wouldn’t work out the same for us as it does for our canine companions. First, it would look mighty darn strange. Second, we walk upright so it would be a chore to bend down to derrière level. Third, we don’t have the right kind of olfactory equipment. Finally, our rearskis don’t have the proper chemical components.

So, let’s start out by talking about that wonderful canine equipment.

Profile close up of dog noseYour dog possesses a fine sniffer

Your dog’s sense of smell is around 10,000 to 100,000 times more sensitive than yours. Wow! I bet you’re glad yours isn’t that keen because if it was, Uncle Pete’s B.O. would drive you out of the house!

Their incredible smellers contain 150 million olfactory receptors and your, poor, lowly nose contains only 5 million. Also, dogs devote about 1/3 of their brain to the detection and identification of odors while we humans utilize only about 5% of our brain for this purpose.

If all this wasn’t enough, dogs also have an additional tool that enhances their sense of smell called the Jacobsen’s organ. This remarkable structure is located inside the nasal cavity and opens into the roof of the mouth behind the upper incisors. This is a secondary olfactory system. It’s designed specifically for chemical communication and functions differently from the nerves in the olfactory tissue of the nose. Thus, it does not respond to ordinary smells. In fact, this organ responds to a range of substances without odor. When your dog curls her lips and flares her nostrils she is employing her Jacobsen’s organ.

The Jacobsen’s organ communicates with the part of the dog brain that deals with mating. It can identify pheromones and gives male and female dogs the information they need to determine the availability of the opposite sex for breeding. Furthermore, it enables newborn puppies to find their mother’s milk and distinguish her from dogs who are not their mothers.

So, the nose and the Jacobsen’s organ are two separate parts of your dog’s odor detection system that work in tandem and make her an awesome smelling machine!

Dogs smell to communicate

While we use words to communicate, dogs use smell. And, it’s really efficient because they can get a whole lot of information very quickly that way. This includes the sex, health, cleanliness, diet and aggression level of the other dog. They can determine if the other dog is friend or foe. By using smell in conjunction with sight, they have a real advantage over humans in getting very honest information about their new acquaintance. Which leads us to the butt itself.

The butt doesn’t lieAnus of dog

So, you ask. Why the butt of all places? Turns out that the dog butt is a pretty interesting structure (Look closely to see just how remarkable). On either side of the dog’s anus is a small anal sac that contains all kinds of interesting chemicals (Yes, there are people who study dog butts and that’s why we know this).

The main chemical is trimethylamine and this has a bunch of short chain acids. These are responsible for the familiar sharp dog butt smell we all know and love. Anyway, these will let the sniffer know a bunch of information about the sniffee. And obviously, a butt always tells the truth about its owner.

A very important aspect of this act is determining which of the dogs is dominant. The dominant dog will initiate the sniffing and the submissive dog will wait his turn. A dominant dog might growl to end the smelling session. And, since the butt is so honest, if one dog doesn’t want to give out too much information, she will sit down and clamp her tail over her rectum.


Now you know why dogs sniff other dogs bottoms! As a human, you may find this whole butt sniffing thing distasteful. But, that doesn’t matter. Let your dog sniff!

We love comments so be sure to leave yours. Please tell us about you and your dog’s experiences with butt sniffing.Cartoon of dogs meeting


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