The two most common rat species in Northern US are the Norway and Roof rats. Both can gain entry to your home, cause damage, and carry diseases. Knowing what kind of rat infestation you have can help identify how they got in, or where they may be nesting.
Norway rats are large rats that can weigh over 500 g. Norway rats can grow to be 40 cm in length Roof rats are smaller and sleeker than the Norway rat, but can reach a length of about 40 cm as well. The tail of a Roof rat makes up most of its length, while a Norway rat’s tail is shorter than its body. Norway rats have very shaggy fur that can be either brown or gray. Roof rats have smooth hair that is generally brown or black. Both rats are omnivorous but have a liking for fruits, nuts, and grains. Rats tend to hide and sleep during the day and are very active at night. Seeing an active rat during the day usually means that there is a very large amount of them in that particular colony. Norwegian rats have scales on their ears and tails, while the Roof rats have scales on only their tails. Norway rats have anywhere from 4-22 litters a year, each consisting of 3-12 offspring. Roof rats have about 4-6 litters per year, with about 6-8 offspring each time. Roof rat droppings are about 12-13 mm long, while Norway rat droppings are about 18-20 mm.
Roof rats get their name from their excellent climbing ability and their tendency to live higher up in structures. Norway rats excel at digging and can burrow into buildings. While both use the walls of a building for colony uses, Norway rats have less of a tendency to live in the attic. Both rats live for about a year and can produce litter year-round. Both rats carry a large assortment of diseases, but roof rats have been known to carry the bubonic plague. While this disease is no longer a huge threat to the public, it can make you very sick, and spread. There are very few cases of this disease in America.
Holes in the eaves, roof, foundation, and walls of your home can allow these rats to gain entry. Non-screened windows and open doors can also be entry points for either variety.