Rats and mice
Rats are a worldwide pest due to their capacity to cause structural damage, spread life-threatening diseases and compete with man for food.
The species most commonly found in Europe is known as the Norway Rat (Rattus noivegicus). A less commonly found species, the Black or Roof Rat (Rattus rattus), is largely restricted to port areas.
Rats live alongside man, invading his buildings and eating his food.
Rats transmit diseases that are potentially fatal to man, such as Weil’s disease (leptospirosis). They also carry organisms that can damage man’s health, such as salmonella bacteria, viruses and parasites such as nematodes and worms.
Damage by rats to the fabric of buildings can be costly. Fires can easily be started after a rat has gnawed a cable. Gas and water pipes are also at risk, and rat burrowing can undermine foundations and damage water courses.
Physically very strong, rats have been known to survive for two days in open water, to swim a mile in open sea and to get through a gap of less than 25mm.
Mice are similar to common rats in many respects.
The house mouse, Mus domesticus, like rats, contaminates foodstuffs and causes serious structural damage. However, unlike rats, they can survive with very little water, are almost unknown in sewers, are far more erratic in their behaviour, have a much smaller foraging range and are not afraid of new things.
Being so small they are very easily carried, unnoticed, in egg boxes, food packaging, laundry baskets, etc. Entering a new location through gaps as small as 6mm, mice build nests which are hard to find, populating an area with new colonies quickly with devastating effect. Because mice can reach sexual maturity 42 days after birth, populations grow much faster than those of rats, which take about twice the time to reach maturity.
The difficulty of preventing access, coupled with the rapid population growth and natural dispersal of mice, means that a large building may contain a number of colonies, each of which must be treated as a separate infestation.