Rat Facts
Washington is home to both native
and non-native rats, in this facts section we are referring to non-native rats.
Native to the Orient, Asia Minor, and Siberia, rats were introduced to North America on the ships of the early settlers. These rats continue to enter new areas on board ships, trains, and trucks and other means of transportation around the world. In Washington, they are now found everywhere that humans have established permanent residence or industry.
Non- Native Washington State rats include the Norway rat (Rattus norvegicus), also known as the brown rat, sewer rat, or wharf rat, and the black rat (Rattus rattus), also known as the roof rat.
Norway rats average 16 inches in length, which includes the animal's long, tapering, tail that is shorter than the length of the rat's head and body combined. Norway rats are often grayish-brown in color from top to bottom; white, black, or other colored Norway rats are occasionally found. The rats sold as pets are specially strains of Norway rats.
Roof rats or “Black rats” are similar in length to Norway rats, but are more slender and darker in color. The tail is longer than the length of the head and body combined and their noses are more pointed than that of a Norway rat. As their name suggests, roof rats are great climbers and are regularly found on roofs in attics and in the upper levels of structures. Roof rats prefer a saltwater influenced warmer climate like we have here in the Puget Sound, and are more likely to board ships than Norway rats, Roof rats are often seen in port areas and coastal towns around Washington State
Facts about Norway and Roof Rats
Rat Food preferences and eating habits
Native to the Orient, Asia Minor, and Siberia, rats were introduced to North America on the ships of the early settlers. These rats continue to enter new areas on board ships, trains, and trucks and other means of transportation around the world. In Washington, they are now found everywhere that humans have established permanent residence or industry.
Non- Native Washington State rats include the Norway rat (Rattus norvegicus), also known as the brown rat, sewer rat, or wharf rat, and the black rat (Rattus rattus), also known as the roof rat.
Norway rats average 16 inches in length, which includes the animal's long, tapering, tail that is shorter than the length of the rat's head and body combined. Norway rats are often grayish-brown in color from top to bottom; white, black, or other colored Norway rats are occasionally found. The rats sold as pets are specially strains of Norway rats.
Roof rats or “Black rats” are similar in length to Norway rats, but are more slender and darker in color. The tail is longer than the length of the head and body combined and their noses are more pointed than that of a Norway rat. As their name suggests, roof rats are great climbers and are regularly found on roofs in attics and in the upper levels of structures. Roof rats prefer a saltwater influenced warmer climate like we have here in the Puget Sound, and are more likely to board ships than Norway rats, Roof rats are often seen in port areas and coastal towns around Washington State
Facts about Norway and Roof Rats
Rat Food preferences and eating habits
- Roof and Norway rats will eat just
about anything humans or other animals will eat, plus many less tasty items
including animal feces, garbage, and will also cannibalize other rats.
- Rats living away from humans are
known to eat seeds, nuts, and bugs, as well as baby birds and bird eggs.
- When given a choice, rats will feed
themselves a nutritionally balanced diet, eating fresh items over stale or
contaminated food.
- Rats are nocturnal and begin
foraging shortly after dark and most of their food collecting occurs before
midnight. They often store or hoard food in food cashes.
- Rats cannot live long without water
if their diet doesn't contain adequate amounts of liquids. .
Rat Territory and Structure
- Roof rats and Norway rats will travel
anywhere from 50 to 300 feet from their nests to look for food and water and inspect
their territory. However, they can travel much farther if needed.
- Rats generally live together in a
group dominated by a large male that guards a group of females and aggressively
prevents other males from mating.
- Rats seen during the day are
generally socially low ranked individuals who have been denied access to food
by dominant rats during the night forcing them to forage in the day or have
been scared out of hiding by a threat. Sometimes rats can also be found
stumbling about do to toxicity from poisons or pesticides by pest control
companies.
Rat Nesting Sites
- Roof rats build nests in attics,
trees, and overgrown bushes or even vines. Roof rats do not normally dig
burrows for nesting sites like Norway rats will if off-the-ground sites exist.
- Norway rats prefer to nest at or
under ground level, and in the lower floors of buildings and crawlspaces.
- Rats can have several nesting sites.
They may spend a week in their main nesting site, and then move for a day or
two into an alternate nest sites.
- Due to their daily need for water,
rats prefer to nest where water is easily available. Higher concentrations of
rats typically coincide with a constant water source nearby
Rat Reproduction
- Both Norway rats and roof rats breed
year-round in Washington, but reproduction is more concentrated in the warmer
months of spring summer and fall
- A litter of 5 to 10 young are born after
a gestation period of around three weeks.
- Baby rats are weaned at about 20
days of age and can breed at three to four months old.
- Younger rats will mate either in the
same location in which they were born or will migrate to a new, open territory.
Rat Mortality and Lifespan
- Washington’s rats are often killed
by vehicles, traps, poison, or other rats. Some domestic animals capture rats.
- Owls, hawks, foxes, coyotes, raccoons
and opossums prey upon rats; snakes will eat immature rats as well
- The average life span of a rat in
the wild is less than one year, and females typically live longer than males
This information was provided by the Washington State Department of Fish and Wildlife, Russell Link, And Michael Holmquist
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