Ratfacts

Identification:

The roof rat (Rattus Rattus) is one of two introduced rats found in the
contiguous 48 states. The Norway rat is the other species and is better
known because of its widespread distribution. When distinguishing the
Norway rat from the Roof rat, pull the tail back over the body. The tail of
the Roof rat will reach the nose. The tail of the Norway rat will not reach
beyond the ears. A third rat species, the Polynesian rat, is present in
the Hawaiian Islands but not on the mainland. Rattus Rattus is
commonly known as the roof rat, black rat or ship rat. Roof rats were
common on early sailing ships and apparently arrived in this country by
that route. This rat has a long record as a carrier of plague.

Three subspecies have been named, generally identified by their fur
color:

The black rat, R. Rattus Rattus Linnaeus, is black with a gray belly.
The Alexandrine rat, R. Rattus alexandrinus Geoffroy has an agouti
(brownish streaked with gray) back and gray belly.
The fruit rat, R. Rattus frugivorus Rafinesque, has an agouti back and
white belly.
Crossbreeding between subspecies has often occurred, resulting in
unreliability in identification by color. However, Roof rats do not cross
with Norway rats.

Range:

Roof rats range along the lower half of the East Coast and throughout
the Gulf States and upward into Arkansas. They also exist along the
Pacific Coast and are found on the Hawaiian Islands. The roof rat is
apparently not quite as adaptable as the Norway rat, which is one
reason it has not spread throughout the country. Its geographic
distribution suggests it is more suited to tropical and semi-tropical
climates. Occasionally isolated populations are reported from areas not
within their normal distribution range; however, these instances are
rare. Most of the Great Plains states are free of roof rats but infestations
can occur.

Habitat:

Roof rats are more aerial than Norway rats in their habitat selection and
often will live in trees or on vine covered fences. Landscaped residential
or industrial areas provide good habitat, as does vegetation of
riverbanks and streams. They will often move into sugarcane and citrus
groves. Roof rats are sometimes found living in or around poultry or
other farm buildings as well as in industrial sites where food and shelter
are available. Being agile climbers, Roof rats frequently enter buildings
from the roof or accesses near utility lines which they use to travel from
area to area. They have been found in sewer systems, but this is not
very common.

Feeding Habits:

The food habits of roof rats resemble those of tree squirrels, since they
both like a wide variety of fruit and nuts. They also feed on a variety of
ornamental and native plant materials. Like the Norway rat, they are
omnivorous and will feed on most anything if necessary. Roof rats
usually require water daily, though their local diet may provide an
adequate amount if high in water content.

Reproduction and Development:

Born in a nest about 21 to 23 days after conception, the young rats are
naked and their eyes are closed. The 5 to 8 young in the litter develop
rapidly, growing hair within a week. When they are 9 to 14 days old,
their eyes open and they begin to explore for food and move about near
their nest. In the third week they begin to take solid food. The number
of litters depends on the area and varies with nearness to the limit of
their climatic range, availability of nutritious food, density of the local rat
population and age of the rat. The young may continue to nurse until 4
or 5 weeks old. Young rats generally cannot be trapped until about 1
month old. At about 3 months of age they are completely independent of
the mother and are reproductively mature. In tropical or semitropical
regions, the breeding season may be nearly year-round. Usually the
peaks in breeding occur in the spring and fall.

Feeding Behavior:

Roof rats usually begin searching for food shortly after sunset. If the
food is in an exposed area and too large to be eaten quickly, yet not too
large to be moved, they will usually carry it to a hiding place before
eating it. Many rats will cache or hoard considerable amounts of solid
food, which they may or may not eat later. When necessary, roof rats
will travel considerable distances for food. They can often be seen at
night running along overhead utility lines. They may live in trees or attics
and climb down to a food source. This is important from the standpoint
of control, for traditional baiting or trapping on the ground or floor may
intercept very few roof rats. Roof rats have a strong tendency to avoid
new objects in their environment and this can influence control efforts.
These rats may take several days before they will approach a bait
station or trap.

Senses:

Rats see poorly, relying more on smell, taste, touch and hearing. They
are considered to be colorblind, responding only to the degree of
lightness and darkness of colors. Roof rats also have an excellent sense
of balance. They use their tails for balance while traveling along
overhead utility lines and are very agile climbers.