The Norway
Rat is also known as the house rat, brown rat, wharf rat,
sewer rat, and water
rat. It was first introduced
into the United States by European settlers
and trading ships in
or about 1775.
It is now the most widely distributed rat species in North America and
can be
found in all states.
The Norway rat is larger,
stronger, more aggressive, and better adapted
for producing young
and surviving in colder climates
than is the Roof rat or other rat species.
Identification of the Norway rat,
should you have a desire to do so, is simple. This rat variety
has a stocky body, weighing between
12 and 16 ounces as an adult. The body fur is course
and ranges from reddish to grayish
brown, with buff white under parts, but there are many
color variations including the
all black Norway rat. The nose is blunt,
the ears are small and
close-set and do not reach the
eyes when pulled down. The tail is scaly and shorter than the
combined length of the head and
body.
Breeding periods for the Norway
rat are normally in the spring and fall of the year, decreasing
during the hot months of summer
and the cold of winter. After mating and a gestation period
of around 22
days, the mother gives birth to a litter consisting
of from 8 to 12 pups.
The
young are naked and blind at birth
and open their eyes in about 9
to 14 days; they are weaned
10 to 15 days after that.
The pups are curious at about this stage and begin to take short ex-
ploratory trips around their surroundings
and are taught by the mother how to find food, water,
and how to hide from danger.
The average female may have from 4 to 7 litters
per year and
may successfully wean 20
or more pups annually.
Norway rats live for more than three
years tin captivity, but in the wild, they
live from 5 to 12
months.
Predators and disease, severely curtail and influence average life span.
Rats, like mice, are social animals
and live in colonies. Thus, some of the mouse behavior
is similar to rats, but there are
important differences. The Norway rat is a ground-dwelling
animal and frequently nests outdoors
in underground burrows. On farms, they inhabit barns,
silos, and other structures.
In cities, this rat may spend it's entire life inside urban buildings.
Indoors, Norway rats prefer to
nest around the lower floors
of buildings, but when populations
are large, it will also occupy
attics, suspended ceilings, wall voids and crawl spaces.
Nests are built of almost any soft
material, such as paper, cloth, leaves and
grass or hay and
are often chewed into smaller pieces
in order to make a loosely matted mass which can be
better molded into a space which
suits that particular mammal.