Why Do Dogs Sniff Butts?

If you’ve ever taken your dog to a daycare or dog park, you’ve probably noticed their first order of business is to sniff other dogs’ butts. Sure, they may be saying “hello,” but does it have to be so… invasive?

As weird as it may look to the human eye, butt-sniffing is actually a healthy, normal behavior for dogs. And if the dogs engaged in the behavior are supervised and properly socialized (as well as off-leash), letting pups sniff each other out can actually be a good thing. Dogs who get to know each other are less likely to fight, and a thorough butt sniff can offer all the information your pup needs to make a new friend.

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“Dogs primarily gather information about the world by sniffing (unlike humans who rely on sight and sound, so out of all of their senses, [smell] is probably the most important for how they learn to recognize and interpret the world around them,” Alexandra Bassett, dog trainer and behavior consultant at Dog Savvy LA, says. “Their sense of smell is so powerful that it can detect scents that are hours or even days old, plus they can track scents over long distances.”

Why do dogs sniff everything?

A dog’s olfactory system is incredibly advanced, especially compared to humans. For context, humans have about six million olfactory receptors in their noses, which may sound like a lot, but dogs can have up to 300 million. 

“Their sense of smell can help them identify and track specific individuals, including their owners, family members, and other dogs, as well as changes in scent related to illness or stress,” Bassett says. “A dog’s sense of smell is also closely linked to their brain’s emotional and memory centers, which means that smells can evoke strong emotional responses and memories in dogs.” 

Your pup can even smell scents layered on top of each other, picking up information in places where we can’t smell anything. But sniffing isn’t just about learning about the world around them, although that’s a big piece. Dogs also use their noses to navigate their surroundings simply because sniffing is enjoyable for them. 

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Why do dogs sniff other dogs’ butts?

Why do dogs smell each other? This behavior is often seen as a greeting, but it’s way more than a simple hello. Research suggests that a dog’s brain may process smells in a similar way to how the human brain processes sights. 

Every animal (humans included) has their own unique scent, and dogs can learn a ton about others through these smells — as well as other behaviors, l ike licking. These identifying scents just happen to be more potent around the anus. Through a thorough butt sniff, dogs can learn about the health and even temperament of other dogs. That’s a lot of information located back there!

“Dogs sniff other dogs’ butts as a way of gathering information about each other,” Bassett says. “Dogs have two small, oval-shaped sacs on either side of their anus called anal glands. These glands produce a fluid with a very strong smell that is unique to each dog and believed to emit pheromones — chemical signals that convey information about an individual dog’s identity, sex, reproductive status, and emotional state.”

Why do dogs sniff your butt?

Sniffing other dogs’ butts is one thing, but why do dogs sniff you? Dogs have a tendency to go straight for human butts and crotches, much to everyone’s embarrassment, but they’re just drawn to the smells emanating from this area. Just like dogs, humans release unique, identifying scents.

“It’s essential to remember that dogs are wired to follow their noses, and sniffing is a natural behavior for them,” Bassett says. “Human mouths, groins, and butts emit strong scents, which is why dogs instantly gravitate to them. While it may not be the most polite or socially acceptable behavior, it’s not necessarily a cause for concern.” 

Dogs may sniff their human parents’ butts simply because they love you. Canines stay connected to other dogs by exchanging smells, and sniffing their human mom or dad is a way of expressing their closeness to you. If you’ve been out of the house, they could also use their powerful noses to figure out where you’ve been, who you’ve seen, and what you’ve eaten. Research has even found dogs can tell their humans’ emotional states or whether they’re ill through smell. 

While crotch- and butt-sniffing is just part of a dog’s nature, it’s okay to discourage this behavior to avoid awkward interactions. Try redirecting your pup to another activity.

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What a dog’s sense of smell reveals

While we tend to use our vision to make sense of our surroundings, dogs rely more heavily on their sense of smell. By sniffing another dog’s rear end, your pup can pick up on detailed information, like the other animal’s age, health status, and diet. They can even determine if the other dog is ill, as well as pick up on their mood. Each dog (and person) has a unique scent that can help your dog “recognize” animals they’ve met before.

Dogs may also sniff each other’s butts to establish social structure. When two dogs meet each other, they will likely investigate via smell to learn more about who the other dog is. The dog who sniffs first may even be considered dominant in the interaction. 

Why dogs sniff butts can also be related to pheromones. Canine anal glands contain pheromones that can reveal information about a dog’s identity to other dogs. Dogs can learn about another’s diet, health, age, gender, and even mood through these scents. A dog’s powerful sense of smell gives them context about other dogs (and people) they meet. They can even tell how old a smell is to see how recently a dog has been in the area.

References

• Bucher, Steve. “Dogs Smell Cancer? The Canine Nose Sniffs Out New Methods in Cancer Detection Technology.” USC Viterbi School of Engineering, 3 July 2024, illumin.usc.edu/dogs-smell-cancer-the-canine-nose-sniffs-out-new-methods-in-cancer-detection-technology.

• “Dogs Smell Time.” Exploratorium, 19 June 2014, www.exploratorium.edu/blogs/spectrum/dogs-smell-time.  

• Graham, Daniel. “Do Dogs ‘See’ Smell?” Hobart and William Smith, 10 Nov. 2022, www.hws.edu/news/2022/do-dogs-see-smell.aspx. 

• Hayes, Caitlin. “Study Finds New Links Between Dogs’ Smell and Vision.” Cornell Chronicle, 18 July 2022, news.cornell.edu/stories/2022/07/study-finds-new-links-between-dogs-smell-and-vision. 

• Kelley, Mackenzie. “Human-Animal Communication in Captive Species: Dogs, Horses, and Whales.” JMU Scholarly Commons, 2015, commons.lib.jmu.edu/cgi/viewcontent.cgi?article=1113&context=honors201019. 

• Kokocinska, Agata, et al. “Canine Smell Preferences—Do Dogs Have Their Favorite Scents?” Animals, vol. 12, no. 12, June 2022, p. 1488, https://doi.org/10.3390/ani12121488. 

• Kokocinska-Kusiak, Agata, et al. “Canine Olfaction: Physiology, Behavior, and Possibilities for Practical Applications.” Animals, vol. 11, no. 8, Aug. 2021, p. 2463. https://doi.org/10.3390/ani11082463. 

• Moffitt, Seth. “Research Suggests Dogs Can Be Trained to Sniff Out Cancer in Other Dogs.” School of Veterinary Medicine, 20 Dec. 2023, www.vetmed.wisc.edu/research-suggests-dogs-can-be-trained-to-sniff-out-cancer-in-other-dogs. 

• Rozell, Ned. “A Nose 1,000 Times Better Than Ours.” UAF News and Information, 29 Sept. 2023, www.uaf.edu/news/a-nose/1000-times-better–than-ours.php. 

• Rozell, Ned. “The World According to a Dog’s Nose.” UAF News and Information, 8 June 2022, www.uaf.edu/news/the-world-according-to-a-dogs-nose.php. 

• Salustri, David. “K-9 Behaviors | What Your Dog’s Behaviors Mean | K-9 Mysteries.” Community Care College, 24 Feb. 2023, communitycarecollege.edu/veterinary-assistant/pet-behavior/k-9-behaviors. 

• Tachibana, Chris. “Probing Question: Can Dogs Smell Disease in Humans?” Penn State University, 12 April 2010, www.psu.edu/news/research/story/probing-question-can-dogs-smell-disease-humans.