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Fighting rats involves high-tech traps and carbon monoxide poisoning for some cities


It's a war that stretches back centuries - people versus rats.


UNIDENTIFIED PERSON: The rat is a spoiler and a killer which has flourished by adjusting himself to man's ways. The rat problem is man's problem.

SHAPIRO: Well, there's a new front in that war as cities across the Northeast are seeing a spike in complaints about rats. Walter Wuthmann of member station WBUR in Boston reports some cities are getting creative as they try to fight this rat surge.

WALTER WUTHMANN, BYLINE: Just off this bike path in the dense city of Somerville, Michael Collins wades through the bushes and extracts a metal box. He's an exterminator, and this box is a trap. It kills rats with a jolt of electricity.

MICHAEL COLLINS: No captures in that one.

WUTHMANN: He walks a few yards down the path and opens up another box. It releases a rancid smell.

This guy - how long do you think he's been deceased?

COLLINS: Two days.

WUTHMANN: It's pretty big.


WUTHMANN: Pretty big belly.

Every time these traps make a kill, they email the city. Somerville is just the second city in the country to use this kind of trap called a SMART box. Colin Zeigler, Somerville's self-proclaimed rat czar, says the trap's data helps identify the location of specific colonies. The city can then address problems nearby, like sealing off trashcans, filling in burrows and teaching people how to rat proof their homes.

COLIN ZIEGLER: We think that they're the next step in rodent control and a good city response.

WUTHMANN: The pandemic tipped the balance in the ongoing battle between people and rodents. Following lockdowns, large cities across the northeastern United States started seeing more complaints about rats. Here's Michael Parsons, an urban ecologist at Fordham University who studies wild rat populations.

MICHAEL PARSONS: It makes sense that with the closure of restaurants, rats are going to need new places to feed. And - because they're normally feeding on restaurant wastes in the dumpsters.

WUTHMANN: Parsons and his team analyzed New York City 311 data and found complaints spiked in the places close to restaurants. Parsons says it appears rats moved from areas crowded with restaurants into residential neighborhoods around them. People used to seeing the occasional rat suddenly started seeing many, many more. Now that eateries are open again, Parsons believes some rats stayed in their new territories, but others migrated back to their old haunts. Boston 311 data show complaints about rats were up nearly 50% citywide last year compared to before the pandemic. City crews are trying to respond to those complaints by killing rats with carbon monoxide.


WUTHMANN: Early one recent morning, a couple sanitation workers wheeled a green metal machine out on Boston Common. They snaked its hose down into a rat's den, then they started filling it with gas. Here's Environmental Health Inspector Brendan Sheehan.

BRENDAN SHEEHAN: So what happens is the smoke comes down and fills the den up. And as we see the smoke emanating out of the other burrows, we start sealing them off. That way, we know it's a complete system.

WUTHMANN: Sheehan says the carbon monoxide euthanizes rats by slowly putting them to sleep. Animal rights activists tend to agree carbon monoxide is more humane than other forms of rodent control, especially poison. Rat poison also kills other animals like hawks, owls and eagles that eat contaminated rats. It sickens an estimated 10,000 children in the U.S. every year and kills some pets. Some communities are phasing out rat poison altogether and trying out alternatives like edible rat birth control. Holly Elmore, an animal welfare researcher with the group Rethinking Priorities, believes we need to stop trying to completely eradicate rats.

HOLLY ELMORE: If they can't do that on islands where they, you know, put millions of dollars into eliminating every rat, I mean, you can't do it in your own house. You can't solve the problem by killing every rat.

WUTHMANN: The Somerville rat czar feels the same. Colin Ziegler says his city's electric traps are just part of the solution.

ZIEGLER: You can never solve a rodent problem just through trapping. You have to look at food sources. You have to look at water sources and shelter.

WUTHMANN: Despite all the money spent on cutting edge technology, city exterminators say nothing beats a dry yard and a tightly sealed trash can to keep the rats at bay. For NPR News, I'm Walter Wuthmann in Boston. Transcript provided by NPR, Copyright NPR.

Walter Wuthmann - WBUR