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.