|The Mammals of Texas -
Rodentia : Family Muridae : Rattus
Description. Similar to the roof rat but larger and chunkier; tail
shorter than length of head and body. External
measurements average: total length, 440 mm; tail, 205 mm;
hind foot, 46 mm. Weight, 400-500 g.
Distribution in Texas. Widespread in Texas but
not so common in the southern half of the state as the
Habits. The Norway,
or brown, rat lives both as a commensal in close
association with man and in the feral state, chiefly
where vegetation is tall and rank and affords adequate
protection. For example, the marshy lands on Galveston
Island off the coast of Texas offer ideal habitat for
them. As a commensal this rat lives principally in
basements, on the ground floor, or in burrows under
sidewalks or outbuildings. They appear to be most common
about feed stores, chicken houses, and garbage dumps.
Although more at home on the ground, these rats are adept
at climbing and have been observed traveling along
telephone wires from one building to another. In places
they become exceedingly numerous and destructive.
They feed on a variety of
items including both plant and animal materials. All
sorts of garbage appear to be welcome, but their main
stay is plant material. Grains of various sorts are
highly prized. When established around poultry houses,
they feed extensively on eggs and young chickens. They
even have been known to kill lambs and young pigs!
These rats are prolific
breeders. The gestation period varies from 21 to 23 days
and the number of young from two to 14, averaging seven
or eight. At birth they are blind, naked, and helpless.
They grow rapidly; their eyes open in 14-17 days and they
are weaned when 3 or 4 weeks old. There is no delimited
breeding season, but there is a tendency for a slow-up in
reproduction during fall and winter. The life span is
reported to be 2-3 years.
Although these rats are
preyed upon by a number of animals including the spotted
skunk and the barn owl, as well as house cats, these
predators often are not able to keep the rat population
in check. Considerable destruction of property and
foodstuffs can take place where rats are abundant. In
addition, they constitute a menace to public health. They
are known to be reservoirs of bubonic plague (transmitted
to man by the bite of a flea or other insect), endemic
typhus fever, ratbite fever, and a few other dreaded
diseases. Because of this it is commonly said that Norway
and roof rats are more dangerous than lions or tigers!
Every effort should be made to exterminate them when they
are found on your premises, and it is advisable to
ratproof garbage cans and all buildings to prevent their
Photo courtesy of U.S. Fish and Wildlife Service.