Page 185 - Florida Pest Control Examinations

NORWAY RAT NORWAY RAT
AND LITTER

Photo Courtesy of UNIVAR Photo Courtesy of UNIVAR

NORWAY RAT
Life Cycle

Norway rats will become sexually mature in 3-5 months of age. The
females create a nest in secluded places when inside a building, or
in burrows or tunnels when outside. There can be from four to seven
litters each year, with up to a dozen young in each litter, so the popula-
tion can grow quite rapidly. Adults only live from 9-12 months.
8”

Photo Courtesy of UNIVAR
Actual size 8” body

NORWAY RAT

The Norway rat is also known as the Brown rat, Gray rat, Common rat, House rat,
Wharf rat, Sewer rat, Barn rat and Water rat. They are not actually from Norway, but were
first identified there. Norway rats are the most likely type to get into buildings, and are a much
bigger problem to eliminate once they do.
Norway rats are often completely black. They can also be grayish-brown, but the color
may vary from a pure gray to a blackish- or reddish-brown. The underside is usually gray to
yellow-white. The body is heavy and thick, from 7 to 10 inches long. They weight between 12
to 24 ounces. The tail is shorter than the head and body--about 6 to 8 1/2 inches long. The tail
is dark on top with a lighter underside.
Norway rats are able to gnaw through wood, lead, aluminum, copper, even cinder block
and uncured concrete. They burrow extensively in soil and are excellent swimmers and good
climbers. They usually nest in the basements and lower portions of buildings. Norway rats are
very nocturnal--most of their activity and feeding takes place between a half-hour after sunset
and a half-hour before sunrise. They also have a very strong social hierarchy - the biggest and
strongest Norway rats get the best food and harborage.
They are omnivores--they can eat just about anything, but they prefer meats, fish,
flour, cereal grains, fruits and vegetables. Norway rats will eat almost any human food and
waste--garbage and even grease can provide excellent diets. Rats visit fewer food sites than
mice, but eat more at each site. They consume 3/4 to 1 ounce of food each day and require
water daily to survive, from 1/2 to 1 ounce of water every day. Norway rats are best suited for
temperate zones. Due to their excellent adaptability, they are found everywhere in the United
States, first arriving here on ships in the 1770’s. They are mostly found in the old established
downtown and dock areas, and have become quite prolific in that environment, so they are not
as much a problem for the homeowner.

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