Outside/Inbox: Why do dogs kick and scratch the ground after pooping?
Every other week on NHPR's Morning Edition, the Outside/In team answers a listener question about the natural world.
This week’s question comes from Ann Barker, of Hollis:
“My question is based on the fact that I do a lot of pet-sitting and dog-walking. I’m wondering why dogs scratch and dig backwards after they poop. It seems like they want to bury what they’ve laid down, but they don’t really do that!”
Ann, I have wondered this very same thing! And your theory makes sense. After all, armadillos, woodchucks, weasels and cats bury their feces. Why not dogs, too?
But you also raise a great point. If dogs are trying to bury their poo, why are they doing such a terrible job?
Our dog Gabby (pictured here as a reluctant ambassador for Outside/In) is an excellent digger when she’s using her front paws, but when she scratches the ground after pooping she mostly just ruins the landscaping. The end result? Torn up turf and a still-very-much exposed turd on top.
Turns out, this behavior (officially called “ground-scratching”) isn’t trying to avoid detection. It’s trying to attract it. Ground-scratching is both a visual and olfactory display.
At least one study has shown dogs are more likely to exhibit ground-scratching behavior in the presence of other dogs. While we don’t know exactly what message is being communicated, scientists have observed that dogs will tend to avoid others that are in the middle of, or have just recently finished, kicking backwards after urinating or defecating.
It appears male and female dogs exhibit ground-scratching in equal numbers, but according to one study, older shelter dogs were more likely to do it than young pups. And while the act itself appears to be a performative display, the scratch marks themselves also likely serve as a visual marking after the fact.
The other side of the equation is smell — but it’s not necessarily the smell of the poop (or urine) that dogs are trying to spread when they scratch the ground.
Kari Mcclanahan is an environmental scientist with the California Department of Fish and Wildlife.
“Dogs do have some scent glands on their feet,” she says.
These “pedal scent glands” may have a role in marking territory, or for sharing information like sex or reproductive status with other dogs in the area.
By the way, you may have actually caught a whiff of pedal scent yourself, as naturally occurring bacteria often interact with the chemicals on dog feet to make a smell that some say resembles corn chips.
“A lot of times it’s referred to as ‘Frito Feet,’” Mcclanahan says.
So Ann, I can’t totally answer your question about why dogs do this after they poop — but I can tell you for sure that ground-scratching is a form of canine communication. Coyotes, wolves and wild dogs do it too!
And I can offer you one more fun factoid, as a consolation: Dogs use different nostrils to smell different odors.
“The left nostril is more [for] neutral or pleasant odors,” Mcclanahan says. “The right nostril correspond more towards - not necessarily negative [smells], they could also be new smells, or something that’s a little less pleasant.”
To learn more about pedal scent, check out Kari Mcclanahan's research with the University of Southeastern Norway, “Conspecific recognition of pedal scent in domestic dogs.“
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