New research reveals urban raccoons across the US show early signs of domestication

The intelligent and adaptable urban raccoon may evolve with a shorter snout – a key physical trait of pets and other domesticated animals. The new discovery describes what one biologist says may be the first account of early domestication.

For Raffaela Lesch, an assistant professor at the University of Arkansas at Little Rock, inspiration came while she was walking around campus. She had thrown a can into a trash can, and it landed with a thud instead of a thud. Soon, Lesch understood why, as a raccoon – aka a “trash panda” – poked its head out of the trash.

Lesch thought about how common and comfortable raccoons were 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 between rural and urban populations, where urban populations were placed on this trajectory toward domestication,” Lesch said.

It is completely normal that waste is involved in its revelation. Fossil records suggest that wolves began frequenting humans 30,000 years ago, searching for trash and scraps of food. Over a period of several thousand years, throughout the world, adaptations in the behavior and physical characteristics of wolves have made them suitable for cohabitation with humans. In other words, domestication.

“Waste is really the starting point. Everywhere humans go, there is trash. Animals love our trash,” Lesch said in a statement. “All they have to do is put up with our presence, not be aggressive, and then they can feast on whatever we throw away. It would be appropriate and amusing if our next domesticated species was the raccoon.”

To test this idea, Lesch and a team of students investigated whether urban raccoons developed shorter snouts, a known marker of domestication.

Looking for “domestication syndrome” in raccoons

Naturalist Charles Darwin observed in the 1800s that domestic animals shared a handful of seemingly unrelated physical traits found in their wild counterparts. Pets tend to have shorter noses, smaller teeth, floppy ears, curly tails, and white patches of fur. A 2014 paper published 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 and more docile individuals do better with people, leading to natural selection for taming. This, in turn, appears to affect early embryonic development – ​​in particular, a decrease in the neural crest cells that migrate throughout the body and form the features of the head and face and the pigment cells that give fur its color.

“Selection for taming seems to have created some deficit in these cells, which helps us explain all these different traits we observe,” Lesch said.

Lesch chose to focus on one of these traits – snout length – to determine whether raccoons living in urban environments sharing space with humans might diverge from their rural relatives.

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

Next, 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 the overall length of the head, from the tip of the nose to where the ear attaches to the head. When Lesch and his students mapped the counties where each photo was taken, a clear trend emerged: The snouts of urban raccoons were 3.6 percent shorter than those of rural raccoons.

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

Or, this particular shorter-snouted phenotype or trait could be a sign of something completely different, 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 it’s domestication or if it’s the same phenotype as domestication,” she said.

Raccoons vs Pets

Raccoons are common around human habitation, but Grossman, who studies wildlife remains from ancient civilizations, noted that they differ in some ways from other species that have been domesticated. “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 example, live in packs or herds with clear social hierarchies and are not territorial.

“While these traits are certainly important when it comes to the likelihood of a species being domesticated, we also see some 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 ended up being domesticated,” she noted. Raccoons may not be pack animals, she added, but they are certainly social.

Lesch then hopes to validate the results by analyzing a decades-long collection of raccoon skulls held at the university. She also wants to compare the behaviors of rural and urban raccoon populations.

However, without the power of time travel, Lesch will never know if this is truly the beginning of a process of domestication of these ingenious creatures.

If raccoons are truly on their way to domestication, thousands of years from now they could also start developing floppy ears, white spots and curly tails, she said. “But what excites me is that we get to explore this story while it’s still in its infancy,” she said. “And even though we don’t see where this will evolve into, we can create a record of how it all started.”

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

Sign up for CNN’s Wonder Theory science newsletter. Explore the universe with information on fascinating discoveries, scientific advances and much more.

For more CNN news and newsletters, create an account at CNN.com