Danny Hellman Illustration

They come by night, swift, cunning killers who seldom leave a trace. Authorities use words like ferocious, relentless, aggressive and secretive to describe them. They have been accused of mass murders. Usually silent, when they are heard the sound can be blood-curdling.

A small cadre was paroled into northwestern Connecticut about 20 years ago. Others surreptitiously crossed the border from Massachusetts under cover of darkness. Today, some experts believe there are thousands of them here, and they have spread to virtually every corner of this state.

This isn't a branch of al-Qaida we're talking about. But you might get that impression reading some of the messages posted on the Internet by terrified pet owners.

The creature generating all this hysteria is the fisher, also called the fisher cat, even though it doesn't fish and isn't a cat. It's a member of the weasel family, along with martens and wolverines, and wildlife experts will tell you the fisher is getting a bad rap.

These Connecticut natives were hunted out more than a century ago for their fur, a luxurious dark brown to almost black. Today, a single fisher pelt may bring more than $80.

The name fisher is thought to be a derivation of the word "fitch," an old name for the European polecat.

A full-grown male fisher can weigh eight to 15 pounds, with females somewhat smaller. It climbs trees like a squirrel, which it also eats. Actually, fishers will apparently eat just about anything: birds, berries, chipmunks, carrion, chickens, fruit, turkeys, rabbits, garbage — you name it, and a fisher will eat it. (They also happen to be one of the few predators who like to munch on porcupines. In a few Midwestern states, where porcupines have become a rather prickly problem, officials have introduced fishers to keep tree-damaging porcupines under control.)

There have been occasional reports of fishers attacking dogs.

And they seem to find cats simply delicious.

The inclusion of domestic animals on the fisher's menu is largely responsible for its nasty reputation and the angry sentiments of a lot of pet owners.

"Fisher ran in front of my car on a back dirt road," Kathy from East Haddam wrote on one Web site in May. "Seven-month old kitten missing a few days later. Beware, fisher cat, I will find you..."

Experts like Paul Rego, a wildlife biologist with the Connecticut Department of Environmental Protection, don't believe fishers are as big a threat to cats and dogs as some fear.

"The population has increased," Rego says. "They have been found throughout the state. ... And as they spread, more people encounter them."

One reason for that dramatic advance through Connecticut is that so much of this state's open agricultural land has been allowed to return to woodland, the fisher's preferred habitat. According to Rego, the heaviest concentration of fishers appears to be in the eastern half of the state.

No one is certain exactly how many of these furtive animals there now are in Connecticut. They live 10 to 12 years at most, with females having annual litters of two or three. Rego's best estimate is that the population is somewhere "in the low thousands."

There are so many around that trappers are lobbying to increase Connecticut's current "bag limit" for fishers. At the moment, state regulations restrict the legal trapping of fishers to November, and a licensed trapper can take only two per season. Those expensive pelts are quite the thing, it seems, for trimming coats and other fashionable items for those who don't mind killing a few animals to look nice.

An encounter with a fisher can be more than a little weird for your average suburbanite.

Adding to the fisher's dark reputation are a couple of recent reports of fishers attacking humans. Both occurred in daylight, leading to concerns the animals had rabies, and both victims got off with scratches and a few bite marks.

According to news reports out of Truro, Nova Scotia, 66-year-old Donna Newlands was walking in a local park when she spotted what she believed were two fishers at about 9:30 a.m. one June morning. When one of them came up behind her, she struck at it with her cane, then stumbled and fell. The animal attacked her and she grabbed it and threw it off her.

"It had more teeth than any animal I've ever seen," Newlands told the Truro Daily News.

The second incident also happened in the morning. A 6-year-old Rhode Island boy was waiting for a school bus with his mom and other students. An animal described as a fisher attacked the boy, and the mother had to kick it away.

Not many people are calm about meeting a nocturnal, arboreal creature that can reach three feet in length. It doesn't help that fishers have been described as "furred snakes" with the take-no-prisoners attitude of the wolverine.

Then there is the fisher's cry, an eerie screech that usually comes echoing through a dark forest. (If you're looking for a quick chill, check out the fisher's cry on YouTube, or at www.fishercatscreech.com.)

"That scream you hear in the woods is a blood-curdling sound," said Jennifer Weiffenbach, of Statewide Wildlife Rescue. In addition to rescuing wild animals, Weiffenbach explains her group is also dedicated to educating the public about reintroduced native species like the fisher.

"They are very efficient predators," says Weiffenbach. "They will take down fawns. They crush the heads of their victims."

Weiffenbach warns that many people have an unreasoning fear of predators. "They think bunnies and deer are cute," she says. But hunters like fishers and coyotes draw a very different response, especially if they're doing the hunting in your backyard as opposed to on some National Geographic TV special about Alaska.

"But they're the ones that help keep the balance" by taking out the sick and the weak among the prey animals, Weiffenbach says.

That's not a concept many pet owners can relate to, particularly if it's their cat or puppy that makes the mistake of running into a hungry fisher.

"Fishers will attack cats," Rego acknowledges. "But it's very rare for one to attack a dog." On the other hand, a recent call to Rego's office demonstrates that rare doesn't mean never.

"One gentleman called me in the last few weeks and said a fisher had gone after his Rottweiler, of all things," says Rego.

The New York Times reported on one incident in Rhode Island when a woman went outdoors to find out why her German shepherd was so upset. She found a fisher was gnawing on the dog's face and wouldn't quit until she beat it off with a broom.

There is also the disturbing tendency of fishers to go a little wacko when they find themselves in an enclosed space with a whole bunch of tasty birds. Like the weasel, fishers have a reputation for bloodthirstiness.

Elena Hermonot and her husband, Rick, own the Ekonk Hill Turkey Farm in Plainfield, where they are currently raising about 2,500 of the big birds.

One night two years ago, Elena heard their dog barking like crazy near the turkey pens. As she hurried out to see what was happening, she saw a fisher running away.

In the pen, they found 68 dead turkeys. "We didn't make any profits that year — not any," Elena recalls.

"When the wildlife takes one or two birds, it doesn't hurt much," she says. Those kinds of losses are expected when you're raising poultry. "But when you have 68 in one night, that hurts a lot."

Elena says that was the only time she and her husband have experienced any serious problems with fishers. "Now we have the fencing electrified," she adds.

Brian Delventhal is an outdoorsman whose business is removing wild animals that are making nuisances of themselves. And he has a grudging respect for fishers.

He's been called twice in recent years by clients who believed they had a fisher problem. But Delventhal has not yet been able to trap one.

Not only that, but he became a fisher victim himself about a year ago. "I lost my own chickens to a fisher," he says. "Thirteen in one night." Delventhal says the tracks left behind proved the identity of the culprit.

(One of the many fascinating things about fishers is that they are the only known carnivore with individual "fingerprints." According to a report on www.LiveScience.com, a recent study determined each fisher has its own unique print pattern on the toes of its paws. Not that this fact helped Delventhal any.)

"I thought I had it pretty secure," Delventhal says of his chicken coop. "But he squeezed through a real small area." Not only that, but Delventhal had his hunting dogs in kennels all around the coop.

It's stories like this that give the fisher the reputation of being the ninja of the animal world.

"I saw him several times after that but never was able to catch him," Delventhal says. Adding insult to injury, the fisher has returned occasionally to taunt Delventhal's dogs. "They don't seem like they're going to back down," he says.

The circumstances of that raid taught Delventhal a lesson about defensive measures. "Now I have [the chicken coop] completely sealed with heavy-duty fence. I use chain link." His birds have been safe ever since. Well, at least so far.

Although the fisher's raids on turkey farms and chicken coops are dramatic, it is their apparent taste for cats that is causing the most uproar.

Local animal control officers across Connecticut point out cat owners seldom know for sure that a fisher is responsible for the disappearance of their beloved pet. Clear-cut evidence of a fisher kill is rare.

But if a fisher has been spotted in the area, it's sure to be blamed.

Rego finds that somewhat odd. "Coyotes are far and away a greater problem [for domestic pets] than fishers," he says. The DEP gets hundreds of complaints a year about coyote depredations, while fishers generate only a few dozen calls to the state annually.

East Windsor animal control officer Jim Hendsey isn't so sure coyotes are a greater threat, at least as far as cats are concerned.

"Fishers are more relentless because they can go up trees," Hendsey says. "Coyotes go after cats too, but they can't climb up trees after them."

Norma Sharette is an assistant animal control officer in Cheshire. She thinks cat owners need to be aware of the risk they're taking these days when they allow their pets to roam free outdoors.

"I have a very fat cat," says Sharette, who lives in West Haven. A family of fishers has been spotted in the area near her home, but Sharette says they've never bothered her extra-large pet when he's outside.

"They go after the sick, the weak, the young and the old," says Sharette, "just like coyotes and foxes." She says if you let your cat outside, the possibility it might become dinner for a roaming predator is "the chance you take."

In a strange way, these somewhat irrational fears about the fisher's appetite for felines could end up having a beneficial effect on the environment, particularly when it comes to native birds.

Fishers do hunt birds, of course. But those birds have evolved to survive in the same environment as the fisher.

Cats are a very different story. They are not native to this continent, and their effect on the environment is huge.

The pet food industry estimates there are more than 83 million cats in American households. A 1997 survey indicated only 35 percent of cats in this country are kept indoors.

According to the American Bird Conservancy, the biggest threat to the world's population of birds is loss of habitat. But scientists now believe the second greatest danger comes from invasive species, which include domestic and feral cats.

Officials at the U.S. Fish and Wildlife Service cite a 1990 study that concluded domestic and feral cats killed nearly 78 million small mammals and birds every year in Britain. Studies in the U.S. concluded cats slaughter "hundreds of millions of migratory songbirds."

Ornithologists in Wisconsin have estimated cats kill between eight million and 219 million a year in that state alone.

A great many people (including this writer) think cats make wonderful pets. But letting them roam loose is creating environmental havoc.

Perhaps it isn't such a bad thing for cat owners to be afraid of all those bad, nasty fishers. Maybe it'll convince them to keep their sweet, lethal little feline friends indoors where it's safer for all concerned.