Do you have a mouse in your apartment? These scientists will take it.

Anna Colliton has lived in her apartment on Pelham Parkway in the Bronx for five years, but she suspects the rats have been there much longer.

They also seem to have an unusual favorite food: spare ketchup packets that they keep next to take-out menus in the kitchen drawer. Even if she hasn’t seen a mouse recently, “if you opened that drawer, it would be full of sachets of grated ketchup,” she said.

So when she saw a post on Reddit captioned “We want your mice!” It was published by a team of evolutionary biologists at Drexel University, and volunteered by Ms. Colliton, a musician and visual artist.

Mice are commonly used in medical research because of their physiological and genetic similarity to humans. But it is possible to observe their evolutionary changes over a relatively short period, making them an ideal subject for research into how wild animals adapt to urbanization, for example. Drexel researchers are studying the effects of urban environments on the evolution of house mice in New York, Philadelphia, and Richmond, Virginia: relatively old cities, where time and evolution may have accumulated differences between the mice in each city and those in it. nearly areas.

Ms. Colliton was fascinated by the aims of the study; She said she noticed that “as much culture and personality as pests have,” the residents of her apartment were “very bold and noisy mice.”

Behavioral traits may be the most obvious differences, but researchers also use fecal tests, DNA sequencing and the microbiome to compare the animals’ bodies. For example, they speculated that city mice might be larger than country mice, due to differences in their metabolism.

Megan Pfeiffer Rixey, an assistant professor of biology at Drexel University, runs the lab conducting the five-year project, which He earned $1.1 million grant from the National Science Foundation in 2021. She said researchers expect to see differences in stress levels in mice due to the different stressors they face, including living in close proximity to humans.

“The environment itself is more complex in cities,” she said, which could influence “things like their willingness to explore a new place, or to engage with things they’ve never seen before, or their decision to hide.”

Urban mice may also be exposed to more diseases, which could affect their immune systems, she added.

Since buildings provide safety from predators as well as shelter and food, the researchers needed to collect mice from inside apartment buildings, homes and barns. This means finding volunteers willing to let researchers into their homes to set humane traps to catch mice alive. After distributing “We want your mice” Publications In city neighborhoods, in feed stores and hardware stores, and sharing on Facebook, Reddit, and Blue Sky, researchers are closing in on their goal of collecting about 30 mice from each city. They hope to publish some results within about a year.

Jason Munshi South, an urban ecologist and professor of biology at Fordham University, who has conducted extensive research on mouse populations in New York City, assisted the researchers with logistics and will contribute to the study’s genomic analysis. Rats in urban areas probably eat different things, “so you might see them adapting to an urban diet that’s very high in refined grains and sugars and carbohydrates and things like that,” he said.

“There are likely to be some changes in their basic anatomy, such as the sizes of their heads and teeth,” he added.

Catching mice revealed their penchant for sweets. Although the researchers baited the traps with peanut butter, they asked volunteers to use whatever they noticed was the favorite food of local rodents. One New Yorker added chocolate, said Logan Lacey, a lab technician who would set traps and return to collect the mice. It worked. In another house, researchers found chocolate chip cookies in a trap. They were not baited, but were brought in by two mice who stole them.

City life may make mice smarter: “It’s easier to catch rural mice; “We usually leave the decoys out for one night,” Mr. Lacey said. In cities, traps must be left for two weeks and are still sometimes unsuccessful.

Scientists are collecting just one mouse per household, and will compare the genomes of mice from different parts of the city. Like rats, rats tend to appear in places where there is an abundance of garbage and food scraps. But they seem to gravitate toward older buildings, where natural settlement has created small entrances, the researchers said, and they also spend less time outside avoiding predators, including mice.

“We don’t really know how mice get from one building to another,” Dr. Munshi South said. “Rats move around outside, and it’s obvious how they do that, but with rats, we don’t think they move around in Manhattan that much outside.”

Since animals tend to stay in place throughout their lives, a Bronx rat may look different from a Soho rat. Simon H. Williams, a senior research scientist at NYU Langone Health Who checked How House Mice Carry and Spread Diseases He, who was not involved in the study, said there was a “high probability” that researchers would see “a variation from building to building, or from block to block,” in the genetic makeup of the mice. . In his own research, he noted that rats from a particular location in Chelsea were genetically distinct from other rats collected around the city.

For the Drexel team, the project demonstrated that New Yorkers are willing to contribute and donate their uninvited roommates to science.

“What I learned is that people are really interested in science, and they are really interested in the mice that live around them,” Dr. Pfeiffer-Rexey said. “I think the time is definitely ripe for this type of project, because they live with us and we know so little about how to do it.”

Ms Culliton, whose kitchen trap yielded two rats, said she was keen to learn more about the creatures living alongside her, although she remains less happy about the rodents in her flat “breeding left, right and centre”. (The researchers stress that their focus is on how mice adapt to life in the city, not on pest control, although their research subjects will not survive the tests.)

“I’m curious to see how they compare to country mice,” she said. “It’s an old question, you know?”