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!
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
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 plague and weil’s
disease, 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.