||it originated in northern China; now it is
widespread almost all over the world.
||the body is covered with hairs, while ears
and tail are naked. The tail is shorter than the body. The molars of the
upper jaw have tubercles arranged in three longitudinal rows. The colour
of the upper part of the body is brown-dark grey with scattered black hairs,
while the underparts are pale grey.
||it adapts to different situations, its main
constraint is that it cannot survive for a long time without water unless
its diet contains other liquids in adequate amounts. It is active all year
round; it is mainly nocturnal and it leaves the nest as dusk approaches.
It forages on the ground even if it swims and climbs very well. When at
night it goes out from its nest to search for food it always follows the
same route: the diameter of its home range isn't generally larger than 50
meters. It usually lives in large groups in which a large male is dominant
and maintains the privilege to be the first to have access to food and water.
This male continuously defends its harem of females from other males which
might want to come in. The females defend strenuously group resources against
strangers and they often build their nest together. Dominance within the
group is based on weight and size rather than age. Some rats may be seen
foraging during the day: they are probably socially low-ranked individuals
to which the access to food has been denied by dominant rats during the
||it is found in human settlements, or where
there is abundance of food and shelter and in salt marshes.
||it is a true omnivore, its appetite is prodigious:
it can eat in a day the quantity of food equivalent to one third of its
weight. It can catch fish and small rodents.
||it is a very prolific animal, if food is abundant
it can breed all year round, although in winter litters can be few. The
number of the young per litter can range from 2 to 14, but it is usually
7. At birth they are born blind, naked and helpless, they open their eyes
at 14-17 days and are weaned at the age of three weeks. The nest is built
with leaves, bits of paper and cloth, twigs. If it cannot find a suitable
cavity, it makes holes in the ground, arranging them as a series of galleries
communicating to each other, with rooms for nest building and for food storage,
one or more main entrances and lots ways of escape.