Mice and Rats have lived with humans for centuries and have in their time been responsible for spreading many diseases including the bubonic plague which killed millions of people throughout Europe less than 500 years ago.
Mice and Rats generally live in nests made from shredded paper, sacking, cloth and other assorted odds and ends.
Mice nest mostly inside, in walls, cupboards, stored boxes or in other warm areas like behind refrigerators or cookers in kitchens.
Rats generally nest outdoors in burrows dug underneath houses or sheds and other building or in piles of rubbish or timber, compost heaps and other discarded items in little used places. Some rats however like the warmth and security of the cavities in walls and in the insulation found in lofts.
During the day rats usually stay in their nest, coming out at night to search for food. They don’t stray far from their nests, usually staying within 40 meters. Mice don’t travel very far at all and usually stay within a few meters of their nests.
Their presence is often discovered through their droppings although signs of gnawing, scratching or tracks may also indicate activity.
Rats and Mice usually live anywhere between 6 and 36 months. Some species of rats can breed every two to three months and produce a litter of 8 to 12 offspring each time, so it does not take long for rat populations to increase many times over if left unchecked.
Mice begin to breed at one or two months old. Their litters tend to be smaller but more frequent and therefore their numbers can increase even quicker than rats.
Mice live for one to two years. They can start having babies at 6-8 weeks old and have 5-10 in each litter (pregnancy lasts 3 weeks). Babies are born hairless with their eyes closed. One mother mouse can produce over 100 babies a year.
As to their uncleanliness, rats and mice gnaw through stored food packaging, eating portions of the product, but - perhaps more significantly - contaminating it with their faeces, urine, and shed hairs. They also (mostly at night) contaminate food preparation surfaces such as table tops, food production machinery, and cookware in cafeterias. Cafeteria workers returning to work in the morning may think the counter tops are clean, when, in fact, they are covered with tiny drops of urine and hairs. Also, when rats or mice heavily infest a building, the place may become infested with human-biting mites and fleas (from the rodents), as well as taking on a generalized foul odor from the urine. Large areas inside buildings become drenched with urine over time, creating a disagreeable "mousey odor"
In addition to disease transmission, introduction of ectoparasites, and food contamination, scientists are now finding out that rats and mice can produce asthma and allergies in the same way cockroaches and dust mites do. There will certainly be more research and new findings in this area in the near future. Apparently, people with allergies can develop hypersensitivity to proteins in rodent urine, causing asthma attacks.