Portland, OR -

The Multnomah County rat inspector says roof rats are on the rise in Portland.

Chris Roberts told KGW says he's getting more calls about rats that turn out to be the roof rat variety rather than the larger common Norway rat.

Roof rats are black or dark gray and spend most of their lives off the ground, nesting in trees. They can climb over power lines and squeeze through any hole larger than a quarter.

One exterminator, Mike Giskaas of Columbia Pest Control, says typically a customer will call thinking they have a squirrel in their attic.