Valley Pest Control kindly offered a few thoughts on rats and the importance of pest control.

Some information about rats and mice

History
Two species 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 at 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!

The house mouse is believed to have come here from central asia where it lived mainly on the seeds of wild grasses. The pest species is primarily the house mouse (Mus domesticus) and should not be confused with field mice, shrews and voles.

Some interesting habits
• Places where they can live – Rats (R. norvegicus unless otherwise stated) and mice (M. domesticus 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. Mice can climb up breezeblock and rendering, telephone cables and curtains and can get through gaps no bigger than the thickness of a pen!

• Diet – Rats need to drink water but 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. A mouse will feed from as many as 50 different locations in a night taking as little as 1/10th of a gram from each. Very important in relation to bait treatments and cleanliness!

• Reproduction – A female mouse can conceive 24Hrs. after giving birth and will produce her litter in 21 days. A litter will contain between 4 and 16 young. Young reach sexual maturity in 3 months. Theoretically then two mice on January 1st could become over 1,800 by Dec. 31st! Fortunately natural mortality rate can be as high as 90%. Rats usually produce between 4 -7 litters per year with an average litter size of 7-8.

• The Hazards - Rats have brought us the bubonic plague and weil’s disease (both potentially fatal), and both species 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. Mice produce up to 80 droppings per day. They must gnaw hard surfaces to keep their constantly growing incisor teeth short. They damage electricity cables, lead pipes, wood, plastic and wet cement.