Norway rats are primarily nocturnal and often enter a home in the fall when outside food sources become scarce. These rats are known to gnaw through almost anything – including plastic or lead pipes – to obtain food or water. Norway rats are social rodents and build burrows close to one another.
Outdoors, Norway rats live in fields, farmlands and in structures. These rats frequently burrow in soil near riverbanks, in garbage and woodpiles, and under concrete slabs. Indoors, Norway rats often nest in basements, piles of debris or undisturbed materials. Rodents can gain entry to a home through a hole the size of a quarter.
Credit to: www.pestworld.org