Writing Word Macro Viruses
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The Roof Rat (Rattus rattus), also known as the ship, black, or house rat, is
usually found inside buildings, preferring the upper parts of these properties,
possibly as a result of its tree-dwelling origins before it adapted to its
current pest lifestyle. The Roof Rat is also the rodent species most closely
associated with plague outbreaks, carrying fleas capable of spreading this
disease to man.
Roof Rats typically grow to 17-20cm long, plus a tail 20-25cm long. Bodyweight
ranges between 200-300g and this may help to explain why this rat is more agile
than the heavier Norway Rat. A Roof Rat's tail, unlike the Norway Rat, is
longer than the combined length of its head and body, and is all one colour.
This longer tail aids the Roof Rat in climbing, helping to balance the body or
adding extra purchase to its grip.
The Roof Rat is an extremely agile climber, probably as a result of its
arboreal (tree-dwelling) origins. The origin of the name 'Roof Rat' stems from
this ability as these rats tend to live in the upper floors of the buildings
The eyes are specialised for nocturnal vision, although sight is not as
important as it is to humans. Because of their adaptation to low-light vision,
rats are almost certainly colour blind. Touch is a far more important sense to
rodents. The vibrissae, or whiskers, are the most important organ for this
sense, although tactile hairs are found all over the fur. This sense enables
rodents to find their way in the dark places they inhabit.
A rodent’s sense of taste is apparently similar to a human’s. However, they are
not particularly sensitive to a substance (trademarked ‘Bitrex’), which is the
most bitter substance known to man. This enabled its incorporation into
rodenticides to reduce the risk of accidental ingestion by humans (especially
children), whilst maintaining the effectiveness of the rodenticide.
Although sensitive to sounds of a frequency that humans can hear (up to 20
kHz), rats are also able to hear sounds of a much higher frequency (up to 100
kHz, with a peak sensitivity at 40 kHz). Rats also make many ultrasonic
vocalisations as a form of communication between individuals. It has been
suggested that ultrasonic sound generators could be used to exclude rodents
from buildings, but their usefulness remains to be proved.
Rodents have continuously growing incisor teeth, which they wear down and keep
sharp by gnawing. Anything can be gnawed, even some metals. On Moh's scale of
hardness, the lower incisors of a Norway Rat score 5.5,
whereas steel only rates a 4. In practice though, rats usually
gnaw on materials softer than this. The incisor teeth keep growing throughout
their life, in order to replace wear caused by gnawing on these hard materials.
Whereas the Norway Rat is basically omnivorous, and can make good use of the
foodstuffs people discard, Roof Rats prefer fruits, seeds and grain. It is a
serious pest of orchards and plantations in many regions of the world.
The Roof Rat has a litter size of between five and ten pups, after a gestation
(pregnancy) period of three weeks. The young can be weaned as early as three
weeks later, and can breed themselves after only 12 weeks. Although capable of
producing more, a female rat usually produces no more than six litters a year.
Holes are often gnawed by rats in doors and even walls to allow access to a
building. These holes, showing distinct grooves - the tooth marks - are the
most easily seen signs of rat activity. Droppings (12 - 15 mm long) may also be
seen scattered throughout the infested area. Rats are creatures of habit, and
will often wear visible paths between their burrows and food sources. Inside
buildings, rats will also leave behind ‘smear marks’, accumulations of grease
and dirt smeared off their fur. These are a sure sign of a serious rodent
Pest rodents are important vectors for the spread of many diseases to humans,
several of which produce flu like symptoms. Some of these diseases can be
fatal. The Roof Rat is most famously associated with plague outbreaks. The
bacterium responsible infects man via the bite of rat fleas, which are in turn
infected from rats. It is usually only when the rat population succumbs to the
disease that the fleas seek an alternative host and feed on humans. Among the
most common illnesses passed along in recent times are rat bite fever or
Haverhill fever, which is transmitted through the teeth and gums of a rat
infected with bacteria. This disease is highly infectious, characterized by
high fever and has a fatality rate of seven to 10 percent if untreated. Weil's
disease or leptospirosis occurs when an individual becomes infected by direct
or indirect contact with infected rodent urine. Organisms in the urine enter
the body through the mucous membranes or through small cuts or abrasions in the
skin. This disease is seldom fatal.
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