Josh McCloud heard something pawing up by the rooftop, but it wasn’t reindeer.

“This guy was too big for all the traps we set,” McCloud said of the Norway rat he captured Wednesday morning at a home west of Reserve Street. “After we sealed the house up, he started climbing into the ductwork and wreaking havoc. He was hungry.”

The gray rat was the size of a man’s fist, with a scaly tail about 9 inches long. McCloud had seen bigger ones when he worked in Chicago, but this was the first one he’d caught in Missoula since he started his HoldFast Enviro Pest Solutions business six years ago.

“We were doing a routine trap-and-bait to get mice out,” McCloud said. “I had no idea he was in there. Once they’re here, they’re really hard to get rid of.”

Norway rats aren’t native to Montana. In fact, they’re not native to the United States. And they’re pretty much disliked everywhere else in the world.

“They probably hopped a ride on a train coming into the state,” said retired University of Montana mammalogist Kerry Foresman. “That’s generally how they move. Our colder climate historically kept them out. But we’re getting into a scenario in the next 20 to 50 years where this type of thing will be more common. With increased temperatures and milder winters, invasive species like that will get well established.”

Norway rats don’t trigger the same defensive alarms as northern pike in a trout fishery or star thistle in a horse pasture. They’ve been spotted in Great Falls and Helena, although in small numbers. That said, Montana Department of Agriculture vertebrate pest specialist Stephen Vantassel wasn’t happy to hear about a new observation.

“There is no detente in this battle,” Vantassel said. “Go for victory. You want to control them sooner than later.”

In addition to being fast-breeding, voracious, intelligent, trap-wary, disease-bearing, steel-gnawing challengers to human planetary domination, Norway rats also ravage local bird populations — especially ground-nesters. McCloud recalled watching pest-control training videos of rats leaping out of burrows to catch and kill pigeons. Fortunately, Norway rats aren’t known to carry hantavirus, a deadly human disease transmitted by native deer mice and packrats.

“Norway rats are commensal rodents,” Vantassel said. “That’s the Latin term for 'share the table.' They’re well adapted to the human environment.”

To get them out of that human environment, Vantassel recommended against adding cats. Felines can be equally harsh on birds and other non-target species. Instead, he advised a pestilential version of supply-side economics: Remove the food supplies rodents depend on and remove many of the rodents.

“The last technique is control,” Vantassel said. “When you have an incident where you see or hear mice in walls, declare war. This is not the time to set a trap. Lots of people buy a couple traps, catch one mouse, and think the problem is over. For a 1,200-square-foot house, I’d set two dozen snap traps.”

McCloud said he will return to the Missoula home to look for more rats. He used a “swing-panel” case trap to catch the first rat alive. The family living there had small children, and a rat-sized snap trap can break an adult’s finger. Now that the species is confirmed, however, he’s ready for war.

“They’re the second-most successful mammal on the planet after us,” McCloud said. “They chew into houses and climb really well and if they get into the sewer system, they take advantage of that. They’re a tough pest to get rid of.”