THE PILE OF CAT TRAPS in Carole Pollastrone’s SUV clatters as she slowly drives the mostly treeless streets of Chelsea. A cardboard flat of cat food covers a chunk of the dash. More cans are tucked into the door pockets. The remains of an iced coffee swish in a voluminous plastic cup. Though the temperature is forecast to break 80 on this early spring day, Pollastrone is, as she puts it, “dressed for a nor’easter,” her pink lipstick notwithstanding. She’s been up since before 5, when it was still cold, but that only partially explains her heavy boots.

“I’ll take you to the dungeon,” the 55-year-old Pollastrone says.

Five days a week, usually more, she traps stray cats in Chelsea, East Boston, and Lynn, often responding to calls from people she’s met while trapping. Sometimes she goes even farther afield, if Lynn Animal Control calls to see if she can pluck a loose tabby out of someone’s yard in, say, Nahant. If the cats are friendly or young kittens, she takes them to animal shelters to be adopted. If they can’t stop hissing at an outstretched hand, they go to be spayed or neutered as well as vaccinated for rabies and distemper. Then she releases them where she caught them.

Pollastrone has pretty much devoted her life to helping cats, ever since she fed strays as a kid in Revere’s projects. Right now that means working overtime, since as the area’s temperature rises, so does the number of kittens. Until they are about 8 weeks old, kittens can easily learn to live with humans if they are exposed to us and trained. As time passes, though, the kitties become much more difficult to socialize. It isn’t impossible, but it’s a huge chore and makes older kittens hard to put up for adoption. “I hate returning a four-month-old to the streets,” she says.

We pull over in front of a tired three-decker in East Boston. Pollastrone knocks on a gate to its backyard to make sure that no dog awaits us on the other side. Hearing none, she charges in. I follow her along a trail of junk and through an ajar, weather-beaten door into a dark basement. Two years ago she noticed a mother cat climbing in one of the basement’s windows, and got permission to trap there. Since then she’s trapped 20 cats here, but now there’s a mother with new kittens and a tomcat she has yet to catch.

The air is thick and sour. Pollastrone walks ahead with a flashlight as we carefully step over and around knee-high mounds of broken lamps, open suitcases, moldy boxes, and forgotten toys. Pollastrone shines her flashlight on what appears to be a dead possum curled in a hamper.

“Back here,” she calls and plunges ahead into the garbage and the gloom, aiming the flashlight’s beam ahead of her, leaving me in the black. I follow the gleam of the highlights in her hair, which falls to just below her shoulders. My foot lands on something that feels like a ripe banana; I fear it is a dead rat.

“No luck,” Pollastrone calls.

The traps are empty. As we turn to leave, Pollastrone holds the flashlight so I can see where I’m stepping. The dead rat turns out to be a piece of foam rubber. Still, I avoid treading on it a second time. Pollastrone will return in a couple of hours to check the traps again. When I ask her how she can stand going in the “dungeon,” she says: “I get such astronomical self-satisfaction from helping the cats. It’s really my therapy.”

NO ONE KNOWS for sure how many cats roam the city of Boston, though one estimate says 45,000, with 10,000 living in Dorchester and Roxbury alone. Some of these cats are pets that people let out to prowl the day away. Many more are abandoned pets and their kittens. Such offspring, which have never known the touch of a human hand, are feral.

Until relatively recently, most of these street cats were not spayed or neutered, so they had litter after litter. In our clime, a cat can give birth roughly three times a year, averaging four or five kittens each time. So the colonies grew and grew — in junkyards or abandoned buildings or forgotten basements, anywhere that provided some shelter. Not all municipal animal control is mandated to pick up stray cats, so the problem went largely unchecked. The colonies swelled. But a few years ago, signs emerged that growth was being reined in. A central reason why is Pollastrone and her ilk.

There are many volunteer cat trappers in Greater Boston, but only about five are as devoted as Pollastrone. Though there are male cat trappers, these five are all women, mostly middle-aged. Some also work full time, including in the marketing department of a private equity firm. One plays tennis in the morning, has lunch with her girlfriends, and then pulls on her trapping clothes. This small cadre brings in the largest number of cats among them. Pollastrone guesses she picks up 200 to 300 each year.

Unless the cats are friendly enough to put up for adoption, all the trappers use an approach known as TNR — trap, neuter, and return. It’s not a quick or easy fix, but as friendly cats are removed from a colony and the remaining feral ones are fixed, fewer and fewer kittens are born, and the group stabilizes and gradually shrinks. Great Britain pioneered TNR in the 1950s to reduce its population of stray and feral cats humanely. The technique took two decades to cross the Atlantic, yet even then TNR was a small, underground movement in the United States. Trappers had to pay vets out of their own pockets to have the cats fixed, typically at full price, say $400. When low-cost spay and neuter procedures were developed in the 1990s, trappers could finally afford to have many more cats fixed.

Today, more than 650 US towns and cities have adopted TNR as an ordinance or policy, according to Alley Cat Allies, a Bethesda, Maryland, organization that started in 1990 to help promote the technique. Major humane organizations, such as the American Society for the Prevention of Cruelty to Animals, officially support it. But there are naysayers, such as People for the Ethical Treatment of Animals, which believes it is inhumane to release feral cats outdoors except in specific circumstances. The American Bird Conservancy objects to TNR for a long list of reasons, not least of which is how effectively felines hunt our feathered friends.

The TNR effort in the Boston area has gotten a boost in the past five years as shelters have become more involved with helping stray cats. Both the Massachusetts Society for the Prevention of Cruelty to Animals and the Animal Rescue League of Boston organize free or low-cost spay/neuter services for feral cats. One such initiative allows the MSPCA to fix both pets and strays from Dorchester, Roxbury, and Mattapan for $10 each at its clinic in Boston.

As it has become easier and less expensive to get these cats fixed, the trappers have escalated their efforts. Kit Lilly, president of the board of Charles River Alleycats, a nonprofit dedicated to homeless cats in Greater Boston, says trappers working with the organization now catch about 1,300 animals a year. Lilly, a former banker who spent her free time trapping cats in Cambridge and Brighton, partnered with other trappers to coordinate their efforts, helping found the volunteer organization in 2002. Alleycats has become essentially a clearinghouse for all things stray cats. The organization fields calls from people about strays and colonies and works to teach and equip them to trap the cats. If they cannot, it will dispatch volunteer trappers.

Years of combined effort by shelters, organizations like Charles River Alleycats, and independent trappers like Pollastrone are finally showing results, which any visitor to a shelter like the ones run by the MSPCA can see — empty cat kennels. At the MSPCA, the number of incoming strays has declined at all three of its shelters (Boston, Cape Cod, and Methuen). Fewer cats going into the shelter has translated into fewer cats being put down — euthanasia has dropped by more than 80 percent at the MSPCA since 2010. On the streets, trappers are finding fewer kittens than in years past, a clear sign that their hard work is beginning to pay off.

Cat trappers are unsung heroes who mostly want to stay unsung. One says she doesn’t want her photo taken; she doesn’t want people to know what she looks like. Another talks on the phone but demurs when I suggest meeting.

Kit Lilly (with her rescue cat, Randall) is board president of the Charles River Alleycats,
a nonprofit dedicated to homeless cats in Greater Boston.

A third won’t let me use her name. They hope through anonymity to avoid being labeled “cat ladies,” as one says, or because some people object to trapping and may even like having the kitties around.

Cat trappers also don’t like to say where they are working, for fear that people might abandon their pets there or, worse, do something awful to them, like poison them. That’s why Anna Lam repeatedly asks me not to write down this address in Milton, close to the Dorchester line. Someone on this block had called Charles River Alleycats to report numerous stray cats and kittens roaming backyards. Alleycats asked Lam, who traps the most cats of any of its volunteers — 500 to 600 a year — to see what was up. At first she couldn’t find any cats. So she walked around the block and noticed a bunch in one yard. She knocked on the door. The woman living there was feeding at least a dozen on her back porch.

On a raw March morning, Lam and I sit in her small car in the woman’s driveway, watching four cats dance around the traps she’s set. Lam tucks paper dishes with food and other goodies at the back of the long cages. Then she makes sure they are on flat ground. Otherwise, the trap will rock and spook the animal before it can be captured. A cat has to be hungry enough to go in. These cats seem hungry, but vigilant, perhaps because they have seen what happened to other cats that stepped inside. Lam has already caught a number of cats from this yard, including a calico with a gaping wound. These remaining kitties are doing their best to eat the canned food and slimy chunks of mackerel from outside the traps.

Lam is small, with an emphatic way of talking. She rarely smiles. She often sighs heavily. Her Chinese-Vietnamese family immigrated to Boston when she was 18. Lam raised a family here. After her two children left for college, she began volunteering at the Animal Rescue League, which eventually led to trapping. Now she can’t stop, though she worries it puts stress on her marriage. Lam works as an administrative assistant and devotes her weekends to the cats, but sometimes also goes out on weeknights if she gets a call about an injured cat. She usually has a few in her basement that are recovering from spaying or an illness. She pays for the food and litter herself and often covers the cost of veterinary expenses.

“Anna has the bug. She knows there are cats on the street suffering and she can’t look away,” says Kit Lilly of Alleycats. The commitment is why more people don’t seriously trap, Lilly says. When she trapped, she constantly had seven or eight cats in her garage recovering from spay/neuter surgeries. “It probably caused my second divorce,” she says. The demands of trapping are also, partly, why Alleycats prefers to work with community members, to show them how to catch abandoned and feral cats in their own yards. A community problem requires community participation, Lilly says, and there are areas that still need a lot of help, such as Brockton. The hard-core trappers shouldn’t have to do it all, she says.

Lam, however, is old school, and she doesn’t have a lot of faith in her fellow man when it comes to cats. In the car, she rails that the homeowner must have fed them this morning, even though she told her not to. They aren’t acting like hungry cats. They are dillydallying, and then one, a tiger, puts his front paws on the propped-up trap door and closes it from the outside. A white cat behind him does the same. A third, a calico, raises its head and looks toward the car. Our eyes lock.

“Don’t make eye contact with the cats!” Lam barks at me. But it’s too late. Seeing me, the cat races away and the others scatter. Lam sighs and then gets out of the car to reset the traps. It starts to rain. Cats don’t like the rain.

“This could take hours,” she says, and sighs.

POLLASTRONE MAKES HER WAY into the dungeon’s hopeless filth several more times on the afternoon I step on the “dead rat.” The traps are empty each time. In between, she searches in vain for a mother cat on Grove Street that someone in the neighborhood had called her about.

In her early days, Pollastrone regularly saw kittens smashed on the roads in Chelsea and East Boston. There were far more stray cats than hours in the day to catch them. Shelters wouldn’t always have room for the friendly cats she picked up. She was discouraged but pushed on, devoting more and more time to trapping. Now shelters call her to see if she has cats to bring in. Most of the colonies she encounters in Chelsea and East Boston are not producing kittens.

“Someone told me at the start that it would take about ten years, and I didn’t believe them,” she says. “They were right.”

But all it takes is a few unspayed, abandoned pets or an overlooked feral or two to make another colony, so Pollastrone cannot relax. Which is why when night falls, she wades through the dungeon’s heaps of junk one more time. When she shines her flashlight deep into the basement’s darkness, two sets of eyes blaze from inside the traps — the tomcat and the mother cat. The next day, she captures the kittens.