c. Damage to insulated wiring, earthen dams, and forest products costs
additional dollars each year, and the damage to the insulation of electrical wiring
creates fire hazards.
d. To the costs of disease and of damage, destruction, and contamination
should be added to the cost of rodent control and totals billions of dollars.
a. General. Domestic rodents, the Polynesian, and the lesser bandicoot are
most abundant in eastern and southeastern Asia. All evidence indicates that the
Norway rat, the roof rat, and house mouse are native to Asia and have spread from
there throughout the world.
b. House Mouse. It appears that the house mouse first moved from Asia into
the Mediterranean area and then into Western Europe. From there, man carried it to
the New World during his early explorations. Because the mouse is so small and
requires so little food, it has spread much farther than the rats. Today it is found from
the Tropics to the arctic regions all over the world. In North America, it is found
throughout the US, southern and western Canada, and the Alaskan coastal regions and
Aleutian Islands. It probably has the widest distribution of any mammal except man.
c. Roof Rat. When one tries to trace the story of the spread of the roof rat
through history, the thread is just along about the 11th Century. At that time, however, it
was busy over most of Europe. A guess is that it entered Europe via the Mediterranean
area during the Crusades. In the European area, the roof rat has two distinct colors;
the black rat of Western Europe, and the brown Alexandrine rat common around the
Mediterranean. When this species was carried to the Americas, however, this situation
changed. These introductions into North America began well before 1750, and roof rats
were well known throughout the French, English, and Spanish colonies. Here the colors
from all parts of Europe were dumped together in the same ports, where they interbred
freely. As a result, today in North America all the colors can crop up in one population.
Often a single litter of young roof rats will contain both black and brown animals.
d. Norway Rat. There is evidence that the Norway rat is a later, more highly
developed species originating in or near the center of origin of the Rattus group. This
comparatively latecomer is adapted to the plains of Central Asia. It is characteristic
among mammals that the most advanced species of a group are found closest to the
center of origin, where they replace the more primitive forms. So it appears to be with
rats. As the more highly developed, more aggressive Norway rat spread outward from
Asia, the more primitive roof rat disappeared over much of its original range. The
Norway rat first appeared in Europe in the 1700's. It spread so rapidly that the
Europeans called it the "Wanderatte" or migratory rat. Soon after it reached Western
Europe, it was carried to the New World, where it quickly began spreading outward from
the seaports, especially along the east coast of North America.