Why Do Dogs Roll Around in Grass?

Ever let your dog out into the yard to run around, but then instead of running around they just roll around on the ground and get covered in grass shavings? Maybe they did it in the mud. All of this can be incredibly inconvenient, so why do dogs roll around in grass? Or mud. 

Camouflage

As with many things about dogs, smell has something to do with their grass-rolling. It’s generally accepted that dogs still have many of their hunting instincts from before we domesticated them and turned nature’s most formidable pack hunters into fluffy couch companions. We view a lot of their behavior through that lens, and rolling around in grass is one of them. 

To this end, a popular theory for why dogs like to roll around in grass is as a masking technique. Dogs smell like dogs, and their prey is going to smell them coming. Putting two and two together, it seems prudent to mask the dog-smell from prey with something. Extra prudent for that mask to be grass, which is already everywhere. 

There’s also the inverse theory, that dogs rub in the grass and stuff to plant their scent onto things. Like how they pee on everything as a means of marking. 

Except here’s the thing, the camouflage theory doesn’t actually hold up all that well under scrutiny. If your dog really was trying to mask their scent, why is it a somewhat common phenomenon for dogs to roll around in things that smell very distinct—like garbage? Even poop, which generally has a lot of animal-smells on it that may as well turn your dog into a giant hunter-animal-beacon. 

Yes, Poop Rolling Is a Thing

You might be willing to write of “rolling in smelly things” as a thing domesticated dogs picked up because some hunting instincts got lost in translation. But it turns out that, in the wild, wolves will actually (kind of) do the same thing. 

When given the opportunity, wild animals will roll in things that have totally foreign smells. In 1986, a study presented two groups of wolves with eight smells from four different categories. They were herbivores, carnivores, food, and manufactured smells. The herbivore and carnivore smells came from herbivore animal feces (like sheep) and carnivore animal feces (like cougars) respectively. You might think intuitively that, if the scent rolling was meant to mask the wolves, they would cover themselves in scents from their environment. Maybe they would go for the herbivore scents so they smelled like their prey. It doesn’t really matter, because you’re probably not expecting them to go for the manufactured smells—which in this study were motor oil and perfume. You also might not expect the wolves to rub up on the carnivore smells. Both of those categories would turn the wolves into giant “something is coming” beacons, right? 

Turns out, the wolves rubbed up against the manufactured odors the most, followed by the carnivore odors. The broad conclusion drawn here was that the wolves were generally rubbing themselves on more novel scents; ones that were not traditionally encountered in their environment or ones that indicated something in the immediate environment had changed. 

To that end, scent rolling (grass included) is more likely a means of communication than it is a means of masking. 


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