Rats are one of the most intelligent, and therefore problematic of household pests. In Wisconsin, the main rat species is the brown rat, also known as the Norway rat. These rodents are much larger than mice, up to 11 inches in length with an additional 4 to 10 inches of tail and up to 18 ounces in weight. They have coarse fur, usually brown, black or grey in color in the wild. Their tails are fleshy, and they have snouts that are elongated but rounded, rather than pointed as a mouse’s snout. They have small eyes and ears, and a body that is sturdy, rather than slim.

Brown rats are foragers, and will eat virtually anything they can find, from insects to nuts and seeds to birds eggs to common human foods like pizza. Rats will even eat each other if food is scarce. They can often be found living around areas with lots of garbage, as they can easily find food there. This can lead to problematic run-ins with humans.

Rats are also problematic due to their breeding habits. A female rat can have up to 5 litters in a year, and they can have up to 14 young at one time! By this math, a rat population can grow from two rats to over 15,000 in just 12 months. These rats will often not live longer than their first year, but they can live up to three years ideal conditions. Rats live in large groups, typically in an underground location such as sewers and cellars. However, they will also build burrows if pre-existing underground residences aren’t available.

One of the biggest concerns with rats is that they play host to a wide variety of diseases. Historically, rats have been thought to be one of the reasons that the bubonic plague, or black death, spread so rapidly. Currently, the Center for Disease Control links brown rats to rat bite fever, salmonellosis, murine and scrub typhus, among others.

Rats are a serious problem if they are able to gain entry to your home. They will eat and contaminate any food within your home, and their urine and droppings are often how disease is transmitted. Not afraid of humans, they will fight rather than flee if threatened. Areas of poor sanitation or where there is a higher concentration of refuse are frequent hubs of activity for these large rodents. Signs of rats within your home include droppings, which are capsule shaped, shiny black and around a quarter to a half inch in length, and gnawing. Tracks or trails in dusty areas can also be a sign of rat activity. These pests need less than an inch of space to gain entry into a location, and once they are in they can be incredibly difficult to remove. Very intelligent and fast learners, and they are wary of traps, baits and glue boards. These rodents will not go away on their own, either, and require professional help for removal.

Did You Know?
A study was conducted in 1964 that found the most-liked foods of brown rats include scrambled eggs, macaroni and cheese, raw carrots, and cooked corn kernels.