The biology of Rodents

There are many different species of structure infesting rodents in Western Washington. The main structure infesting rodents in our region are rats and mice. The greatest distinguishing factor between an adult rat and an adult mouse is that the rat is much larger. As for Rats, the two main types are Norway and Roof Rats.

Norway Rats

Norway Rats vary in color from gray-brown to red-brown. They range from 2 inches at birth up to 15 inches when fully grown and their tail is shorter than the body.

Roof Rats

Roof Rats are lighter in color than the Norway Rat; usually a light gray, and their tails are longer than their bodies. About 2 inches at birth, these rats will grow to an overall length of about 15 inches when the tail is included.

Mice

Mice are much smaller, adult mice are about 5 to 8 inches in total length. Mice are dull gray in color and may have white markings.

Where do they live?

Norway Rats are scavengers and usually make their nests in or near the ground. In a structure they will commonly nest in the crawl space.
Roof Rats are tree dwellers. Their natural habitat is in trees, but they will make nests in the higher places in a structure such as the attic.
Mice live in grasslands around vegetation. In a structure they will live in the crawl or attic space.

What Do They Eat?

They are omnivorous and will eat most anything.
Norway Rats are scavengers, that will eat everything from soap to candy, milk, meat, vegetables, poultry, eggs, and all grains, nuts and fruits.
Roof Rats are a little bit more choosy about their diet and will feed on seeds, nuts, vegetables, fruits, insects, invertebrates and other materials such as soap, paper, hides and beeswax.
Mice feed predominantly on seeds, grain and insects. All rodents will gnaw through wood, plumbing pipes, electrical wires and many other parts of a structure.

Why are they pests?

Rodents carry diseases and destroy property. As mentioned before, rodents may gnaw through electrical wiring, plumbing, sheet rock/wall materials wood and even on valuable outdoor plants. When nesting in a crawl space, they will destroy the sub-floor insulation and soil the vapor-barrier. Deer Mice are known carriers of the Hanta-virus (HPS) which is a life-threatening respiratory disease. It is rare for humans to contract Hanta-virus, however this disease can be fatal if not diagnosed properly and in a timely fashion.

Control Measures

Control of rodents can be difficult. Some rodents are smart enough to trigger snap traps and steal the bait. Some rodents are able to recognize snap traps of various kinds and avoid them. Rodents have also been known to have a resistance to poisons.

Inspection is the #1 tool in controlling rodents. We need to establish how they are getting in and what kind of rodent is invading your structure. Then we can formulate the best plan for ridding you of your unwanted houseguests and keeping them out for good.