Why Is a Stranger’s Crotch More Interesting Than Mine?

Part 2
By Julie Hecht, December 2011, Updated April 2020

Here is a recap of the study we discussed in Part 1, Oh, hello! Why yes, that's my crotch *:

Crotch factoid #1: A dog enters a room, sees his owner lying on the floor, and he gives considerable attention to his owner's upper body.
Crotch factoid #2: A dog enters a room, sees a stranger lying on the floor, and he initially goes for the crotch.

Why the difference? Why is a stranger's crotch initially so much more interesting than mine?

Why is this so appealing?


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Let's first consider why owners' crotches were initially not sniffed. It's possible that dogs do not sniff owners' crotches because owners have taught them not to!

For many humans, crotch sniffing is considered irritating, embarrassing and offensive. Not surprisingly, 1,009 people "like" the facebook page, I Hate Dogs That Sniff My Crotch.



In response, the web suggests ways to prevent crotch sniffing. Some suggest teaching the dog to perform a behavior incompatible with crotch sniffing (such as lying down) and others suggest using words or actions to dissuade the dog from crotch sniffing. Regardless of the training method, it is plausible owners could eliminate crotch sniffing from their dog's owner-directed behavioral repertoire.

At the same time, it seems highly unlikely that an owner would train a dog not to sniff the owner's own crotch, yet allow dogs to continue sniffing strangers' crotches. Since the study under consideration found lots of stranger-directed crotch action, what could be going on?

A better explanation comes from the olfactory content of the human body. We are aware of some of our odors, such as BO, and others evade our consciousness. This is where dogs come in.



Dog + Stranger's Crotch
Upon coming across a stranger, dogs are interested in doing an ID check, similar to when you are at a holiday party and you ask someone for their business card. This little piece of thick paper (which you examine visually) provides initial information about the person standing before you. Putting the business card in your mouth or sniffing it offers no information about the other person. As a human, you can look, talk and listen to learn about others (although olfaction can play a role, particularly when someone puts on too much perfume, or, ahem, not enough).

For dogs, crotch sniffing had nothing to do with getting to third base. Instead, it is more akin to looking over a business card. One of the places we humans keep our business cards is in our crotches, in a set of glands called the apocrine glands. While apocrine glands are found in a number of hairy regions of the human body, they are heavily concentrated in the anogenital (crotch) region. These glands secrete pheromones **, chemicals that enable olfactory communication with others, particularly concerning identity. Investigating a stranger's crotch simply orients a dog to the individuality of that person.

Dog + Owner
On the other hand, when a dog enters a room and sees an owner, through the gift of sight, the dog registers, "Person I know well is right there!" The dog knows who they are dealing with and does not need to go for the crotch. They can move on and gather more general information about you, the owner, such as where you've been and how you're feeling (unlike teenagers, our bodies don't lie).

Of note: You, the human reading this blog, release volatile organic compounds, or VOCs***. Your breath, for example, contains many VOCs which are both generated by your own body and picked up from the environment at large. In a sense, you are a walking science experiment, picking up odors and producing them on your own, and a dog who knows you is immediately interested in smelling your chemicals.

Whether a stranger to a dog or its owner, we humans are odorous sacks of information, and dogs will sniff many different parts of our bodies. But during an initial interaction with either a known or unknown person, dogs differ in their preliminary points of contact.

This holiday season, will you be sharing your business card with dogs?


Many thanks to Tom Brownlee for always setting me straight when it comes to scent and olfaction.

*Filiatre et al., 1991. Behavioural variability of olfactory exploration of the pet dog in relation to human adults. Applied Animal Behaviour Science, 30, 341-350.

**Grammer et al., 2004. Human pheromones and sexual attraction. European Journal of Obstetrics & Gynecology and Reproductive Biology, 118, 135-142.

***Martin et al., 2010. Human breath analysis: methods for sample collection and reduction of localized background effects. Analytical and Bioanalytical Chemistry, 396, 739-750.

Julie Hecht, MSc, is a PhD candidate studying animal behavior at the Graduate Center, CUNY, and author of the Dog Spies blog at Scientific American. She would really like to meet your dog. Follow on Facebook and Twitter.