Why dogs like to roll in mud and feces: scientific explanation

Most dogs have a strange habit of rolling in mud and feces. However, scientists have found that this may be part of a form of communication that is not yet well understood.

Most dog owners are familiar with this behavior: the dog comes back from a walk dirty and with a pungent odor of whatever it was able to roll around in. Scientist Simon Gadbois studies the behavior of wild wolves, foxes, and coyotes in Canada and has spent much of his career trying to understand how dogs and other canines perceive the world through their noses, but even he is sometimes puzzled by their behavior, the BBC reports.

Olfactory camouflage

Dogs have been pets and friends of humans for many years, yet there is surprisingly little research on why they get so much joy from rolling around in another animal's feces.

One of the main theories is that this habit is an evolutionary relic from the time of wild predators. That is, although people have tamed dogs, they have not managed to get rid of the basic instinct.

"It may have had a very important function at some point a long time ago. Over time that function has vanished, but they still do it," says Gadbois.

Wolves have been known to roll in the feces of other species, and the main reason given is to provide olfactory camouflage for predators as they stalk their prey.

But after the results of a study in 1986, this idea was called into question. Researchers gave wolves a number of different odors. As a result, they found out that wolves were almost not interested in rolling around in the feces of herbivores such as sheep or horses as scientists did not notice that they were trying to absorb these smells at all. Food odors were also unattractive to them. But they were happy to choose artificial odors, such as perfume or motor oil.

For an animal that would like to hide its scent from its prey, choosing something so alien to their natural environment is strange, to say the least. However, the researchers also found that the second favorite scent of wolves was the feces of other carnivores, such as pumas and black bears.

"Here at Wolf Park, the wolves are willing to roll in the scent of alien canids and domestic cats. It raises a strong possibility that wild wolves may roll in predator scent too. This would not be a helpful hunting disguise," explains Pat Goodman, senior animal curator at Wolf Park in Indiana, who has spent many years studying wolf scent.

Helping smaller dogs avoid other predators

So could lying in strong odors have another camouflage purpose? That is, not to hide them from prey, but to help smaller dogs avoid other predators.

This idea is supported by a 2016 study that used remote cameras to record the unusual behavior of gray foxes living in the Santa Cruz area of California.

These foxes are usually solitary animals, but it was noticed that they regularly visited places that were marked by the scent of male cougars. The footage shows the foxes rubbing their cheeks against the marked ground.

According to scientist Max Allen, foxes use the scent left by these large predators as a form of camouflage for their own scent to hide themselves from other large predators such as coyotes.

"The foxes cannot really fight back, so they are exploiting the puma scent to get some form of protection. Smelling like a puma might give them time to escape," he says.

However, this doesn't explain why larger canids such as wolves also try to absorb the scent left by other predators. And it is also quite possible that male foxes simply rub their heads and necks against objects to leave their own scent.

Social aspect

As for domestic dogs, there may be a more social aspect to their behavior: they may simply be trying to share an interesting scent with you.

For animals that largely perceive the world through their noses, this can be a useful way to share information with the rest of their pack in the wild.

According to Pat Goodman, Wolf Park founder Erich Klinghammer speculated that scent rolling may be a form of "non-insightful communication," where wolves are not necessarily aware that they are carrying a scent to others on their fur. But she has also noticed that scent rolling is associated with food.

"I watched our wolves eat up small pieces of elk. When they received a large side of elk, they both ate and scent rolled," says Goodmann. "I speculated that food scent on the wolf's breath and on its fur indicated that there were more leftovers to scavenge, for wolves that wanted to backtrack to the source of the odour," she says.

Complex form of communication

Scientists are also considering the possibility that scent rolling may be part of a more complex form of communication.

This is supported by a study where wolves were offered different scents over a two-year period and were quite selective in choosing which ones they would roll in. Although they spent a lot of time sniffing the droppings of herbivores such as deer and guinea pigs, it was the unusual smells they had not previously encountered that made them most eager to roll in - for example, the smell of curry, rosemary, and sheep's wool.

The researchers suggest that this behavior may be triggered by encountering unfamiliar smells and may be a way of communicating with the rest of the flock.

Group odor

Simon Gadbois believes that this habit has a simpler explanation. In the wolf packs he studied in Canada, the lead animal was usually the first to roll in a strong scent, followed by the others.

"It could be that this is about establishing a group odour. In the wolves I studied, if one started rubbing in something like a deer carcass, the whole pack would follow and rub in it," he says.

This supports the idea that collective animals such as wolves and dogs may use scent rolling as a way for the animal to join the group. It can also be a way to increase their social standing - if they bask in the scent of an older animal, they can literally absorb its higher status.

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