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232
Rodent Control
General
Of the several hundred species of rodents scattered throughout
the world the types met with in this country are limited and, in
urban areas, only the common rat, the ship rat and the house
mouse are normally encountered—usually as commensals.
Common Rat
(Rattus norvegicus—brown rat). Weight approximately 12 ozs.
Blunt snout—thick, opaque, hairy ears—tail shorter than head
and body combined. Colour usually brown but can occasionally
be black. Suspicious of new objects—can burrow, climb,
swim and jump up to 2½ ft. Its presence is deduced from a
number of signs including shape and distribution of droppings.
Lives both indoors and out and in sewers—evenly distributed
between urban and rural areas. Said to have originated in
Central Asia and introduced into this country early in the
18th century.
Ship Rat
(Rattus rattus—black rat). Smaller than common rat with
weight approximately 8J ozs. Pointed snout—large, thin,
translucent, hairless ears—tail longer than head and body
combined. Colour varies from brown through all shades to
black. Habits erratic but also suspicious of new objects.
Agile climber but does not burrow. Its presence detected
from traces and droppings. Lives principally indooirs and
aboard vessels but rarely in sewers. Found mainly in ports
and in towns connected therewith by canals and rivers.
Originally from S.E. Asia; said to have been imported in
ships returning the Crusaders from the Holy Lands.
House Mouse
(Mus musculus). Average weight ½ oz. Pointed snout—tail
longer than head and body combined. Colour varies between
grey and brown. Habits erratic but not so suspicious of new
objects. Climbs, may possibly burrow and can jump up to
1 ft. Lives indoors and out and is equally distributed between
town and country. Has its origins in the Caspian Sea area.
All three are nocturnal and need to gnaw in order to maintain
sharpness of incisor teeth. This they do to pipes, cables and
sheathings, etc., but the advanced position in the jaw of the incisors
means that gnawings are neither tasted nor swallowed—
repellent materials are therefore ineffective for control purposes.
Their spread has been via the paths of commerce and in the wake
of warring armies.