rats

Common Norway, Sewer or Brown Rat (rattus norvegicus)


The brown rat has been in this country from the early 18^th century and they originate from Russia not Norway as the name suggests. It is far more common of the two species , and can be found almost anywhere in rural and urban areas , indoors and out doors and are often in the sewers


Physical dimensions of an adult common rat
	Weight	-	100-500g average 335g
	Combined head & body length	-	200-270mm
	Tail length	-	150-200mm


They are usually brownish grey on the back and grey on the belly area but some black ones can be found.


Life cycle of the common rat
	Born- sexually mature	-	8 - 12 weeks
	pregnancy	-	21 - 24 days
	litter size	-	6 - 11
	weaning period	-	3 - 4 weeks, then mates again
			Dies at approximately one year old


From this it can be seen that a young pregnant female entering an area, unless checked with in a period of one year can develop into a sizeable rat problem.




Diet
The common rat will eat almost anything but cannot survive without water or a very moist diet. Although they do prefer a cereal diet with water available. They eat approximately 10% of their body weight each day and regularly store food.




Damage done by the common rat falls into various categories, the largest being the contamination of food stuff by eating , droppings, hair and urine - this is estimated at 5% of the worlds food produce.
Structural damage is caused by gnawing at timber structures, door bottoms and frames, to electrical cables, water pipes and the general fabric of the buildings.
Diseases such as Weil’s disease is commonly known but there is also the risk of, Salmonellosis , Plague, Rat Bite Fever.
Signs of infestation include droppings , smell, evidence of gwawing, sightings and damage to stored food.



The Black Rat, Roof or Ship Rat (Rattus Rattus)

Is only found in seaport areas or in towns linked to seaports by a canal.
It is usually black in colour with white or grey underneath and smaller than the brown rat.
It is an extremely good climber and is very often found in roof spaces, it always lives indoors and very rarely enters sewers.