The clever, adaptable urban raccoon may be evolving a shorter snout — a key physical trait of pets and other domesticated animals. The new finding describes what a biologist says could be the first account of domestication in its earliest stages.

For Raffaela Lesch, an assistant professor at the University of Arkansas at Little Rock, inspiration struck while she was walking around the campus. She had tossed a can into a waste bin, and it landed with a thud instead of a clang. Soon, Lesch realized why, as a raccoon — aka a “trash panda” — popped its head out of the garbage.

Lesch reflected on how prevalent and comfortable raccoons can be in urban environments — even in the middle of the day — and it sparked her curiosity: Could she be witnessing the early stages of the same process that led to the domestication of dogs thousands of years ago?

“That was the first moment where I started to wonder if we might have a difference in rural and urban populations, where urban populations have been put on this trajectory towards domestication,” Lesch said.

It’s only fitting that trash was involved in her epiphany. Fossil records suggest that wolves started hanging around humans as many as 30,000 years ago, scavenging for waste and leftover food. Over a period of thousands of years, all around the globe, adaptations in wolves’ behaviors and physical features made them suitable for cohabitation with people. That is, in a word, domestication.

“Trash is really the kickstarter. Wherever humans go, there is trash. Animals love our trash,” Lesch said in a statement. “All they have to do is endure our presence, not be aggressive, and then they can feast on anything we throw away. It would be fitting and funny if our next domesticated species was raccoons.”

To test the idea, Lesch and a team of students investigated whether city-dwelling raccoons were developing shorter snouts, a known marker of domestication.

Searching for ‘domestication syndrome’ in raccoons

Naturalist Charles Darwin observed in the 1800s that domesticated animals share a handful of seemingly unrelated physical traits not seen in their wild counterparts. Domesticated animals tend to have shorter noses, smaller teeth, floppy ears, curly tails and white fur patches. A 2014 paper in the journal Genetics proposed an explanation for the development of this specific set of attributes, known as “domestication syndrome.”

The authors of the 2014 study posited that less aggressive, more docile individuals fare better around people, leading to a natural selection for tameness. That, in turn, seems to affect early embryonic development — specifically, a decrease in neural crest cells that migrate throughout the body and go on to form features of the head and face and pigment cells that give fur its color.

“The selection for tameness seems to have created somewhat of a deficit in these cells that helps us explain all these different traits that we observe,” Lesch said.

Lesch chose to focus on one of these traits — snout length — to determine whether raccoons in urban environments that share space with humans might be diverging from their country kin.

She and 11 undergraduate and five graduate students from her fall 2024 biometry class combed through more than 19,000 photos of raccoons on iNaturalist, an online database of wildlife observations submitted by hobbyists and citizen scientists around the country. They found 249 images that showed the animals in perfect profile.

Then, the researchers used a computer imaging program to measure the length of the specimens’ snouts, from the tip of the nose to the tear duct, and total head length, from the tip of the nose to where the ear attaches to the head. When Lesch and her students mapped the counties where each picture was taken, a clear pattern emerged: Urban raccoons’ snouts were 3.6% shorter than those of raccoons in rural areas.

“That doesn’t sound like a lot, and in a sense, it is not a lot, but if you think about these animals potentially only being at the very early beginning stages of domestication, that is still a fairly clear signal,” Lesch said. She was lead author of a study published October 2 in the journal Frontiers in Zoology.

Or, this particular shorter-snout phenotype, or trait, could be a signal of something else entirely, said zooarchaeologist Kathryn Grossman, an assistant professor of anthropology at North Carolina State University, who was not involved in the research. “I don’t know if this is domestication, or if it’s a phenotype that is the same as domestication,” she said.

Raccoons vs. domesticated animals

Raccoons are a common presence around human homes, but Grossman, who studies faunal remains from ancient civilizations, noted that they differ in some ways from other species that have undergone domestication. “Animals that have been domesticated have a very specific social structure,” she said, “and raccoons are not one of those animals.”

Wild wolves, sheep and cattle, for instance, live in packs or herds with clear social hierarchies and are not territorial.

“While these traits definitely matter when it comes to the likelihood of a species being domesticated, we also see flexibility in what that can look like,” Lesch said.

Wild cats and wolves have very different social and hierarchical structures, according to Lesch. “Yet both of them ended up being domesticated,” she noted. Raccoons may not be pack animals, she added, but they are certainly social.

Next, Lesch hopes to validate the findings by analyzing a collection of raccoon skulls spanning several decades that are housed at the university. She also wants to compare behaviors between rural and urban raccoon populations.

However, without the power of time travel, Lesch will never know whether this is in fact the start of a domestication process for these resourceful critters.

If raccoons really are on their way to domestication, in thousands of years they may also start developing floppy ears, white patches and curly tails, she said. “But the part of this that makes me excited is that we get to explore this story while it is in its beginning stages,” she said. “And while we might not see what it will evolve into, we can create a record of how it all started.”

Amanda Schupak is a science and health journalist in New York City.

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