Rats are spreading through the Treasure Valley, and they’re here to stay. What to know

You may want to keep your leftover Thanksgiving turkey, stuffing and mashed potatoes sealed up this year, or you could be contributing to an increasing problem in the Treasure Valley: rats.

Social media has been awash in reports over the last several months of rats in Eagle, but the reports are spreading to Boise now, too.

“This rat thing is getting crazy,” wrote one user on Nextdoor. “Over the last two weeks I’ve trapped and killed 10 large rats and 10 mouse-sized rats. I have lived in the Gary Lane-Hill Road area for 69 years and have never even seen a rat till three weeks ago.”

One user who also lives in Northwest Boise theorized that “rats are most excellent swimmers, the drainage ditch is like an expressway for them to travel into Boise.”

“Someone else found them near my place on the West Bench,” another wrote. “They seem to be established here now and have moved outside of Eagle.”

According to Jake Perkes, the owner of Eagle’s Sawtooth Pest Control, calls for rats started in a mostly localized area around downtown Eagle. The rats, he said, are moving east toward Boise off State Street, which is where Sawtooth has received the most calls. But the company has recently had calls from other areas.

“We have got calls from Star, Nampa, Caldwell and up in the Eagle Foothills towards Avimor and Hidden Springs,” Perkes said by text. “They are definitely spreading.”

The rats Perkes has been dealing with aren’t your cute little pet rats or mice. They’re the big, invasive Norway rats that have bedeviled cities like New York and Los Angeles for decades. They’ve inspired characters in popular culture like Scabbers in the Harry Potter series and Splinter in Teenage Mutant Ninja Turtles.

New York City Mayor Eric Adams has called the pests “public enemy No. 1” and appointed a “rat czar” in 2023 to battle the scourge.

Norway rats — also known as brown, street or sewer rats — average around 16 inches in length and weigh about half a pound to a pound. They live in habitats including garbage dumps, sewers, open fields or any area where they can find food and shelter such as homes and basements.

“Norway rats are social pests, often building shelters close to one another,” said Jim Fredericks, a board-certified entomologist and senior vice president of public affairs at the National Pest Management Association, by email. “This means that where there is one burrow, there are likely others close by.”

Norway rats, he said, pose significant risks to homes and human health. They are known carriers of diseases including jaundice, rat-bite fever, cowpox virus, trichinosis and salmonellosis. They can gnaw through almost anything — including plastic or lead pipes — to get to food and water, which can cause serious damage to properties and structures.

They reproduce quickly, Fredericks said, and can give birth to between three and six litters of six to 12 pups every year. That means one female rat could give birth to between 18 and 72 pups annually.

Once established, they thrive in urban environments where food and shelter are readily available, he said.

They appear to be doing just that in the Treasure Valley.

Perkes, who has worked in pest control in the Boise area for about 15 years, told the Idaho Statesman in October that he’d never received a call for rats until last year. In October, he’d had around 40 to 60 calls.

“We’ve had a ton of calls since (then),” Perkes said Wednesday.

According to Lindsay Moser, spokesperson for Boise’s Planning and Development Services Department, the city has received nine complaints since the end of September — mostly along Hill Road in Northwest Boise. She said that number could be higher if other city departments have also received complaints.

Moser said there’s not much the city can do. Once rats become established, she said, they’re here to stay.

“It’s similar to like a skunk or raccoon,” she said by phone.

Rats don’t fall into any specific jurisdiction, she said. The city and county have no rat programs, and the Idaho Department of Fish and Game is more focused on animals like bears or elk, though you can submit sightings to its website.

Growing pains in a growing Treasure Valley

The rats may just be the latest sign that the Treasure Valley is growing.

As cities expand, infrastructure issues such as old sewage systems, waste disposal practices and poor drainage create environments conducive to rat infestations, Fredericks said.

“Despite what many believe or may want to believe, there is no neighborhood that is immune to rats,” he said. “That said, urban areas are certainly more susceptible to invasions by these pests.”

The region has grown and urbanized dramatically over the last decade and saw a massive bump during the COVID-19 pandemic, when remote work helped give residents of other states an incentive to move to places that may have been more affordable and more in-line with their priorities.

The region’s population stood at about 712,000 people in 2019, according to the Community Planning Association of Southwest Idaho. That number grew to nearly 823,000 by 2024.

The rate of growth has since slowed, though the region is still growing. The top five states people are moving to Idaho from are California, Washington, Oregon, Utah and Arizona, according to U.S. Census Bureau data. Many of those areas, Perkes said, have significant rat populations.

It would be virtually impossible to find how Norway rats migrated to Southwest Idaho, but there are theories.

“Rats can be introduced in lots of ways,” Fredericks said. “They are capable of stowing away on trucks and shipping containers and are very common near ports.”

Perkes, and others in the industry, hypothesized that people accidentally brought rats to Eagle by shipping containers that are commonly used when moving long distances. The containers often sit on streets for long periods as people pack and unpack their possessions.

It likely wasn’t one instance of a rat sneaking on board and hitching a ride to Idaho, Perkes previously told the Statesman. Instead, it probably happened several times.

What should I do if I see a rat?

According to Fredericks, Norway rats commonly rest in soil, which provides insulation during the cold weather, but they will readily enter buildings to nest in walls, beneath or behind equipment, in basements and in crawl spaces. They are often attracted to dampness in search of water and can fit through a hole the size of a quarter.

It is also more common to find rats indoors in the winter months, when they are trying to escape the cold. According to the National Pest Management Association, rodents invade about 21 million homes every winter.

Fredericks said there are several things people can do to prevent an infestation from taking root. Among them:

• Keep firewood stored well away from the structure and remove debris piles to reduce ideal nesting spots.

• Seal any holes on the outside of the home to block potential points of entry.

• Eliminate sources of moisture like leaky pipes, especially in crawl spaces and basements.

• Properly seal food products in containers to avoid contamination, which can lead to disease transmission.

• Put garbage in tightly enclosed trash cans that are regularly emptied outside the home so as not to serve as food attractants.

• Keep debris from building up near building foundations.

Moser, with Boise’s planning department, recommended that if you are thinking of laying traps, to use mechanical traps rather than poison.

Poison traps are often made using ingredients that are attractive to rodents such as peanut butter or cereal grains, and people often place them in easily accessible areas, according to the Children’s Hospital of Philadelphia. This has led to frequent accidental ingestion by children or pets, and that can be deadly.

Fredericks said to keep a regular eye out for signs of a rodent infestation and to call a licensed pest-control company if you suspect the pests have found a new home in your home.