Cats, too. Both species “greet” each other by sniffing anuses. Does the anus convey any information to the sniffer — age, sex, fertility, etc.? Or does it just convey a specific identifier, the way a face conveys someone’s identity to another H Sapiens?
Do H Sapiens’ anuses convey any information to a dog? Or is it a matter of the dogs not knowing any better?
A dog’s sense of smell is far more advanced than ours. When compared to humans, dogs have a smelling ability that is about 100,000 times more sensitive. The human nose contains about 5 million olfactory receptors that detect aromas, while a dog’s nose has 150 million scent receptors. Dogs devote about 30% of their brain mass to the detection and identification of odors, while humans use a mere 5% for olfactory purposes…
What perplexes many pet owners is why dogs sniff this particular part of the anatomy. Why rear ends? Why not ears or feet? The answer is anatomical. Inside the rectum are two small sacs called anal glands which secrete a noxious-smelling substance into the rectum through a pair of tiny openings. The glands are emptied naturally when the rectal sphincter muscles contract during a bowel movement. Pet owners are unaware of this occurrence since the odor of the anal glands is masked by the odor of the dog’s stool; however, dogs can tell the difference.
Dogs sniff rear ends as a greeting and obtain vital information from the anal secretions. Is this dog a friend or foe? Is he going to be a good “date”? Is he aggressive? Is he feeling ill? And because the odor is unique to every dog and serves as a form of identification, two dogs can quickly determine if they have met before. The very act of sniffing rear ends can establish the foundation of a canine relationship.
It’s also the reason why dogs sniff vegetation when you take them out for a walk. They can smell pee or poop from a distance and hone in on where it is emanating from. They can find out the gender of the animal, for example whether it’s a female in heat. My male dog will then cover the scent with his own urine or poop. It’s his way of him saying “I was here last!”.
It’s also the place where the strongest scents are coming from. The anus and genitals will have smells that are much stronger than other places. The dogs are honing in on where the strongest smells are coming from. I’m sure that other body parts also have smells that are distinctive to that individual dog, such as the ears, but those smells would be relatively weak. Even if they aren’t getting specific info from the anus about what the dog ate or whatever, the smell would have a specific “fingerprint” that the dog would remember and attribute to that dog uniquely. Then when the your dog smells that same smell when out on a walk, they’ll know which dog was there before them. Sometimes you may notice they get particularly interested in a spot of poop or urine when out on a walk. This may be because it’s from a dog they don’t know and they are trying to learn all they can from the scent.
That’s how they transmit the Launch Codes
Y’know, it occurs to me that I’ve seen a lot of sources talking about all of the information that dogs can get from smelling other dogs, but I don’t think I’ve ever seen any descriptions of any experiments anyone’s done on the topic. Which makes me wonder if all of those sources are all just speculating, or (even worse) just copying others’ speculations.
You think maybe they’re just pulling it out of their asses?
Are you saying it doesn’t pass the sniff test?
One thing is that I don’t think dogs think of odors as bad in the same way. For instance, you can be walking your dog and it will forcefully try to drag you to a splat of week-old roadkill that has been baking in the summer sun. If your dog manages to get to it, they will sniff it with deliberate intent. That behavior seems to be about the enjoyment they get from experiencing an intense scent rather than trying to gain information about the animal which produced the splat.
In some ways, it might be similar to how we are with flowers. We smell flowers because we like the way they smell. We smell the pedals because that’s where the most intense and interesting smells are found. Even though the leaves and stem also have distinctive scents, we don’t smell those other parts of the flower. We smell the flower because it’s enjoyable, not because we’re trying to discern anything about the flower itself.
Very true. I imagine my dog “sees” the trail ahead of us with her nose, perceiving an environment that I cannot. I bet she recognizes other dogs from the neighborhood have been there, and yes, she does go ahead and pee a few drops on top of whomever was previously there. Sometimes she will dig-in all four legs and strongly resist me pulling her away from a clump of grass - it’s like she’s telling me “No! Wait! This is important!!” - maybe a new dog in the area.
It’s interesting that she is much more interested in what I suspect are pee spots than other dog droppings we encounter. I guess there is way more information for her doggy database in urine than in poop.
It might be that they like the scent, or it might be that they react the same way we react to ugly visuals. We’ll point and say “Hey, look how ugly that is”, and keep on looking at it ourselves, without being pushed away by it.
I agree, there’s little if anything that dogs do with strategic intent. It’s because they enjoy something, or fear something, or feel it has nutritional or just plain chewing value.
The question is whether it serves any useful purpose for them, and it’s well-established that dogs identify things by smell. Dogs smell each other because they like it, but it helps them by providing a basis of identification. Sort of llike humans asking each other’s name when they meet. It may just be an automatic habit, you might forget them the moment you walk away. But you can’t remember their name if you don’t ask. That’s what smelling is for dogs.
We have e-mail. Dogs have pee-mail.
What, in anal secretions, would indicate a foe or aggressiveness?
Stress hormones: Higher levels of stress hormones like cortisol and adrenaline can be detected in the secretions, potentially indicating an agitated or aggressive dog.
Testosterone levels: Elevated testosterone can signal dominance or potential aggression, especially in intact males.
Unfamiliar pheromone profiles: Dogs are sensitive to “unfamiliar” chemical signatures that might trigger defensive responses.
Health markers: Dogs with pain or illness may have different chemical signatures that could make them more unpredictable or reactive.
Previous encounter memory: Dogs can remember the scent profile of dogs they’ve had negative interactions with before.
I read somewhere that dogs communicate primarily by scent, and will sniff vegetation that some dog has peed on, glean something from that, and then pee on it themself to leave a message for any dog that happens by later. Some people call this pee-mail. I also believe that poop is different for them than pee. Some dogs, like mine, prefer to poop only where other dogs have pooped. He will smell another dog’s poop and apparently glean something from it. However, there have been many times where I had to walk an extra 30 minutes before he was satisfied with pooping someplace, still he prefers pooping where some other dog has recently pooped, as opposed to a place where no dog has been lately.
I have a small dog that is very scent-focused - I’m fairly sure, from observing her behaviour, that sniffing other dogs is partly about learning and remembering who they are, so she can determine their scent when she encounters it on a marked stump or similar; there are a small number of local dogs that she recognises specifically as ‘best buddies’ and she will often recognise that they are at the park or on the walking trail on the basis of the markings they have just left - so sometimes we’ll be out walking and she will sniff some clump of grass and will become visibly happy and excited and will drag us hurriedly forward, then we meet the ‘bestie’ that she must have realised, from the scent, would be here.
Good OP and good replies.
But I am curious about this. Do dogs get similar information from our butts? I just googled and see that in fact humans also have anal glands.
I’ll never perceive a bicycle quite the same way.
I don’t think this is the case or else they would be doing it all the time. It tends to be part of the introductory ritual primarily. I think there is a sexual aspect to it also, what I wouldn’t speculate on.