What Attracts Roof Rats to Your House?

Roof rats and black rats are the same species, Rattus rattus, under two common names, and they're a warm-climate, coastal animal — established in the southeastern United States, the Gulf states, Hawaii, and small pockets of the Pacific coast, with cold, temperate regions largely off the map. New Hampshire's climate favors the Norway rat instead: Rattus norvegicus has greater cold tolerance and has displaced roof rats from cooler parts of North America, taking over the ground-level burrows and structures a roof rat would use in a warmer climate. Where the two species do overlap elsewhere in the country, roof rats are the better climbers and tend toward upper floors and rooflines, while Norway rats stay near the ground — one more reason a ground-level rat here points to the Norway rat.

That means a rat sign in New Hampshire almost always belongs to the Norway rat, even when "roof rat" gets used out of habit. This isn't the same as saying a roof rat has never been recorded here — isolated introductions outside a species' normal range do occur — but it is not the established, breeding population the rest of this catalogue describes.

The rare, genuine exception is a roof rat arriving via freight or a shipping container — documented introductions like this have occurred far outside the species' usual range when an infested shipment moved rats into a new area. Even then, the rat isn't responding to anything about a house; it was transported in, much like bed bugs are. If you have an active rat problem in New Hampshire, treating it as a Norway rat situation is almost always the accurate starting point — see /top-diy-methods/norway-rat for what that involves.