PORTLAND --The roof rat, also known as the black rat or ship rat was once famous for spreading Europe s Black Plague. The nocturnal rodents spend about 90 percent of their lives four or more feet off the ground. They're dark grey or black with no hair on their ears and can measure 15 inches long from their heads to the end of their long scaly tails.

Roof rats nest outside in trees, wood piles, and dense vegetation. But they also climb power lines and can run right into a house. They can squeeze through any hole larger than a quarter.

Chris Roberts is Multnomah County s lone rat inspector. He takes about 1,000 calls for rat problems each year. The majority turn out to be for the larger common ground rat, or Norway Rat.

Normally I get about four or five calls that turn out to be roof rats, Roberts said.

This year, so far he s seen 40 to 50 roof rat cases.

Roberts said that most residents don t even know that such an animal exists.

People are just surprised, Roberts said. They don t know what they are.

True to the Portland spirit, they're also mostly vegetarian. Roof rats prefer nuts, seeds, fresh fruit and tree bark.

We get calls of something eating someone s tomatoes, Roberts said. That s probably a roof rat.

Photo right: Multnomah County rat inspector Chris Roberts can provide traps free to residents, but roof rats can be hard to catch.

Mike Giskaas, owner of Columbia Pest Control in Portland does work throughout the Metro area. He said he sees most of the Roof Rats in inner North, Northeast and Southeast Portland.

From about 45th Avenue to the river, Giskaas said. That seems to be where they are worse.

Giskaas said, typically a customer will call thinking they might have a squirrel in their attic.

They know the weather is changing, Giskaas said of the rodents. And they are looking for a place to hang their hats for the winter. They breed constantly and they don t just go away on their own.

Roberts said most of his roof rats infestations are in inner Southeast and northeast as well. But information about these unwelcomed guests is anecdotal. Some exterminators said they aren t seeing more roof rats, but have seen major increases in Norway Rats over the years. The cause for the rise in either rats species is guesswork. Some professionals blame a series of mild winters, others believe it s due to the rise in backyard chickens or Portland s new composting policy.

Until someone does a scientific study, we won t know for sure, Roberts said.

The county can provide home inspections and rat traps free of charge. But roof rats pose a particular challenge. County workers are not allowed to enter attics or climb ladders. Roberts refers residents to professional exterminators for major problems and emphasizes that residents should work on preventive measures.

Places roof rats like to live and nest

  • Oleanders
  • Bamboo
  • Holly trees
  • Ivy
  • Any heavy vegetation

Preventative measures recommended by the county

  • Trim tree branches and vegetation away from your home
  • Seal exterior holes in second floor
  • Keep property clean and clear of overgrowth and debris
  • Communicate and work with neighbors

Lock down outside food sources including

  • Chicken coops
  • Compost containers without bottoms
  • Bird feeders
  • Unsealed garbage cans
  • Dog or cat food outside

Click here for more roof rat resources

Multnomah County Vector Control
Chris Roberts

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