Why do dogs sniff each other's butts?

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We’ve all had that embarrassing moment when we’ve had to stop and smile awkwardly at another puppy parent while our pooches start sniffing each other’s butts.

It’s one of those weird behaviours all dogs seem to do, that we humans don’t really understand. After all, our dogs have truly amazing senses of smell, so why on earth would they stick that super-powered schnozz in another dog’s behind?!

So why do dogs sniff butts and is this behaviour really a normal thing for dogs to do?

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Why do dogs sniff each other’s butts?

Dogs sniff each other's butts as a way of getting to know one another, but they learn way more than we humans do while making small talk with a stranger. While we humans might offer a handshake and hand out business cards with our details on, our dogs prefer to get up close and personal.

Although we think shoving a nose into someone’s butt might be a strange way of saying hello, it’s perfectly normal and natural for dogs to do, and you’d be surprised by just how much they can learn about a new friend just from a quick sniff.

But why do dogs sniff butts when they could stick their nose somewhere nicer? Surely it isn’t the most pleasant smell...

It’s a chemical calling card

Your dog sniffs butts precisely because that’s where all the smells come from. And we don’t just mean from poop or pee either.

You’ve probably heard about anal glands, and if you’re unlucky, you might have had to drain your dog’s glands. These glands are an importan part of canine communication and the reason why dogs sniff one another’s butts.

The apocrine gland and the sebaceous gland sit on either side of your dog’s anus and they secrete chemicals that contain your dog’s personal smell as well as all kinds of information about your pooch. When other dogs smell their back end, they sniff the chemicals secreted by these glands and all the different bits of information it contains about your dog.

There’s so much info stored in these scents, that a dog can actually tell the age of another dog, their gender and reproductive status, how healthy they are and their diet. It’s thought that a dog can even tell another dog’s mood and personality from these smelly signals!

As well as these glands sending out all that sniffy info, your dog has super-powered part of their nose called the Jacobson’s Organ. This is dedicated to sniffing these chemicals and isn’t used for any other kind of smell. The Jacobson’s organ even has nerves connected directly to your dog’s brain, which means that when they’re sniffing another dog’s butt, they’re only taking in those chemicals and don’t get distracted by other smells like any poop stink left on their butt.

To really simplify it, it’s almost like a dog has an entirely separate sense of smell just for sniffing chemical signals from other animals and people. And their nose is so powerful they can find out another dog’s full biography just from a sniff.

A dog’s sense of smell is up to 100,000x better than a human’s, so it’s no wonder our canine companions prefer to explore the world by nosing around, and why we struggle to comprehend just how good their noses are.

So why do dogs sniff butts? Because there’s a chemical calling card back there that your pooch can sniff to figure out everything they need to know about their new friend.

It’s not a one-time thing

Everything has its own individual smell for a dog. Even something like a table will have all the different smells of the wood it’s made from, the varnish used, even the smells of any food you ate on it or a cat that brushed against it.

Individual people, pooches, and other pets all have their own unique aroma which a dog’s amazingly strong senses of smell can identify, like a signature perfume or a smelly fingerprint. It means dogs can tell different people and pooches apart by smell alone. It’s a bit like when you were a kid at school and could tell what jumper was yours from the smell, just thousands of times stronger!

The butt is one of the places a dog’s smell is strongest, since that’s where the anal glands are. The back end is also where other smelly signals can be found such as traces of urine or vaginal secretions. It may sound gross, but these secretions and smells all have those chemical calling cards and they all happen to be in and around your pup’s rear end.

What’s even more amazing is that a dog can remember these smells for a really long time. So not only can a dog tell if they’ve met another pooch before based on smell alone, they can even remember who was the more dominant dog, and they’ll keep that memory for years.

To put that in perspective, smell is potentially a human’s strongest sense and we retain memories of smell much better than any other sense. We can smell something and it’ll bring back long-forgotten memories from years ago. With that in mind, we can only imagine how long and how clearly a dog might remember a specific smell, given their sense is so much stronger than a human’s, and a much bigger part of their brain is dedicated to processing smells.

After all, a dog has 150 million olfactory receptors compared to a human’s piddly 5 million, and we only use 5% of our brains to process smell while a dog dedicates a whopping 30% of their brain power to analysing smells.

Sniffing humans

Sometimes a dog will try to sniff a human's butt or crotch and this is probably for the same reason they want to sniff another dog’s butt. However, it’s not really pleasant and can be seriously off-putting, especially if it’s a stranger's dog.

If your dog has a bad habit of trying to sniff between people’s legs, try to distract them and divert their attention somewhere else. Get them to sit or teach them to stop jumping up. Have a treat in your hand and get them to do something positive like “sit” and wait for them to say hello to the other person calmly. Then feed your pooch a treat to reward the good behaviour.

Should I let my dog sniff butts?

Dogs sniffing another dog’s butt is a perfectly normal behaviour and you don’t need to discourage your dog from doing it as long as they’re well-behaved. Although sniffing another dog’s poop or pee can carry a small risk of your pooch contracting an illness from an infected dog, sniffing butts should be perfectly safe as long as both dogs are healthy and vaccinated.

However, not every dog has good manners. Some dogs are happy with a quick sniff then want to move on, while some other pups are more vigorous and a bit pushy. In fact, some dogs are just oblivious to other dogs' speak and can even be bullies.

Some dogs will race over to other dogs and invade their personal space, not leaving the other dog alone. If one dog is being blind to personal space, the other dog might get annoyed and there’s a potential fight waiting to happen.

You should always keep an eye on both dogs sniffing each other and pay attention to their body language. And if either dog is getting a bit pushy it’s time to get them back on the lead and coax them away. Similarly, if one dog starts tucking their tail, flattening their ears, or steps away, they’re getting uncomfortable and it's time to walk away.

Exercise a bit more caution if there are more than two dogs sniffing each other. As the saying goes, three’s a crowd, and dogs are more likely to get overstimulated and overexcited when they’re in a group which can lead to nervousness or aggression in some animals.

Some dogs aren’t big on butt sniffing either, and that’s alright. If your dog isn’t interested in sticking their nose near another dog, there’s nothing to be worried about. Maybe your pup is more of a people person, or just isn’t in the mood to socialise that day. But if you are ever concerned about a sudden change in your dog’s behaviour, it’s always a good idea to talk to your vet or a behaviourist for advice.

So if you’ve ever pondered “why do dogs sniff butts” and worried whether or not you should be letting your dog get so close and personal to another pooch, never fear. Butt sniffing is perfectly normal for puppers and now you know why they always stick their nose in another dog’s business!