Thanks to pizza, NYC mice are biologically different from their country cousins

white-footed mouse
CC BY 2.0 Charles Homler

The metabolic pathways of urban mice are changing due to the “novel diets” afforded by city living.

Members of the New York City wildlife set would seem to have it easy, what with the abundance of street food littering the sidewalks and spilling forth from the trashcans like holiday cornucopias. There are sardonic jokes about pigeons pecking from fried chicken detritus, there are squirrels pilfering french fries while raccoons wreak havoc in the dumpsters, and who could forget pizza rat?

While of course it’s depressing to see animals being forced into the squalid environment that humans choose to live in – concrete and steel woodlands with fast food in place of nature’s bounty – at least there is some kind of ironic solace to learn that they have the long-term flexibility to survive. Which is what new research from biologists at the State University of New York and Fordham University reveals. Namely, that white-footed mice in New York City are adapting at the biomolecular level to urban habitats; their metabolic pathways are changing thanks to the “novel diets” afforded by city living.

For their research, the biologists worked with 48 white-footed mice and analyzed the RNA from both urban and rural residents. Looking for differences in gene expression between the city mice and their country kin, they found that in the urban critters, biological evolution has some overlap with that of humans. Quartz reports:

"Like us, they seem to have selected a gene involved in the synthesis of omega-3 and omega-6 fatty acids, which are important to tissue function and which humans likely selected while transitioning from hunter-gatherers to agriculture about 12,000 years ago, during the neolithic age.

The biologists also found that city mice had genes associated with non-alcoholic fatty liver disease, suggesting Big Apple rodents are probably eating a lot of fatty acids, which are prevalent in fast food. Urban mice also had larger livers with more scar tissue than their country cousins."

Unlike some New Yorkers, the white-footed mice are likely not subsisting on pizza and fast food alone – the city’s parks still supply fruit and nuts that they eat. But the researchers nonetheless think that their findings are an illustration of the ol’ “cheeseburger hypothesis,” in which urbanized animals ramp up their calories by eating human food tidbits, most notably fast-food scraps.

While more research needs to be done to better understand how city living is transforming its tiny rodent residents, one thing’s for sure: White-footed mice in New York City are adapting to local selective pressures. But hey, if they can make it here, they'll make it anywhere...

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