Like the Norway rat, the roof rat is an Old World rat native to Asia, specifically the forests of Southeast Asia. It also spread west through human migration, but it arrived in Europe and North America earlier than the Norway rat. Once the more aggressive Norway rat reached Canada, roof rats began to decline. Whereas Norway rats appear in every province, roof rats tend to dominate in coastal cities or along waterways in warmer climates. Although they generally don’t occur more than 100 miles inland, they may be transported inland and establish local infestations.