New York discovers the rat-killing effect of extreme cold

The extreme winter weather gripping New York City, where 20 people have died from the cold in just 18 days, could have an unexpected side-effect: a decrease in the rat population. Fed up with trying to combat the presence of rodents in parks, streets, and subway tunnels using countless methods, including the appointment of a rat czar, the city views this winter’s historic extreme temperatures as an effective form of natural selection.

Without the usual detritus on the sidewalks — which have been covered in snow and ice for weeks — rats are finding it difficult to feed, leading to stress that can also inhibit their reproduction. As such, not only are they hard to spot on the streets, where they used to roam freely, but this sexual inhibition promises a more merciful spring and summer for those who despise rodents.

Sub-zero temperatures have left a crust of dirty snow on New York City sidewalks; the term “white blanket” is best reserved for the countryside or mountains, not for urban grime. But this brown layer also contains surprises. Joe Donovan, a building superintendent in Manhattan, says that while trying to clear the section of sidewalk in front of his building, as required by regulations, he found two frozen rats. “Those aren’t reproducing anymore; what the experts say must be true,” Donovan laughs heartily, shovel in hand. “I haven’t seen any for days in the basement boiler room and laundry room either. I hear the neighborhood supermarkets are noticing the improvement too.” In grocery stores, so-called “basement cats” are very popular, especially on Instagram; hunters who are employed 24/7, and today, thanks to the cold, are quite idle.

A well-fed female rat can give birth up to seven times a year, according to experts. Seeking refuge from the cold, those living in the subway, which are also numerous, have an advantage over street rats. The young fare worse, left unprotected when their parents abandon them in nests and burrows — where they theoretically store food — to go out in search of reserves. The population decline would therefore affect the most vulnerable individuals: the sick, the elderly, or the very young. “Everything will depend on whether the adults are able to find food, because to survive they need protein and warm nests so that the young don’t die of hypothermia,” explains Martin, an employee at VJ, a fumigation and pest control company that is seeing fewer clients these days.

The predominant species in the city, Rattus norvegicus, the brown or Norway rat, does not hibernate, but this year it has had to retreat to its burrows, forced into hiding by the cold and the reduction of waste in the crust of snow, ice, and grime that covers, like a rusty mountain, the gigantic garbage bags that are put out on the sidewalks every afternoon, despite the program to implement containers designed precisely to prevent rats from having free access to the waste. The situation is somewhat reminiscent of what rodents experienced during the pandemic, when the shutdown of businesses and the near disappearance of food scraps and garbage on the streets stressed them to the point of making them aggressive.

However, experts and authorities warn that no one should expect the eradication of these rodents; only a modest reduction in the unofficial census, which in 2024 put the number of rats in the city at three million. The new mayor, Zohran Mamdani, has not yet revealed his plans in this regard while his predecessor, Eric Adams, turned their elimination into a crusade (he himself suffered from them in his Brooklyn home) by designating them as “public enemy number one.” His efforts culminated in the appointment of a “rat czar,” Kathleen Corradi, in 2023. Like almost all New Yorkers, she too eventually threw in the towel last September, resigned to the undeniable evidence of the plague.

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