Pest Information: Rats

History

Two types of rat have inhabited Europe for centuries.  Some pest control historians believe that the lighter, more agile, and longer tailed ship rat or roof rat (Rattus rattus) has been around since about the 7th Century, others say it has been here ‘since time immemorial’.  The date of the arrival of the heavier, more aggressive brown rat or sewer rat (Rattus norvegicus) is similarly disputed.  Some say it first arrived with the return of the ships during the crusades in the 12th Century, others claim it turned up in the 17th Century.  Gradually the ‘sewer rat’ displaced the ‘ship rat’ from our countryside, towns and cities, though colonies still survive in a few of our  major port cities.  You can see that names can be deceiving!

Some interesting habits

Places where they can live – Rats (R. norvegicus unless otherwise stated) are highly adaptable and we have found nests in places as varied as oven linings and industrial freezers.  Rats will burrow 1-2m into the ground and live in compost heaps, deep litter and of course sewers. 

Diet

Rats need to drink water whereas mice can survive on the water content of stored grain (approx 12-14%) without ever having to drink.  A rat will take all its food (approx 30gm/day) from just one or two locations and will feed once or twice a night. Very important in relation to bait treatments and cleanliness.

Reproduction

Rats usually produce between 4-7 litters per year with an average litter size of 7-8.

The Hazards

Rats have brought us the plague, Weil’s disease, and have been responsible for outbreaks of food poisoning.  They dribble urine upon everything on which they walk and so contaminate bulk food stocks and food preparation surfaces wherever they go.  They must gnaw hard surfaces to keep their constantly growing incisor teeth short.  They damage electricity cables, lead pipes, wood, plastic and wet cement.