Norway rat and roof rat

The Norway rat is well documented across the state and the country. The national wildlife damage handbook records it throughout the contiguous forty-eight states, generally at lower elevations but occurring wherever people live. Texas sources describe it as widespread in Texas. There is no ambiguity about whether it is here.

The roof rat is a different picture, and the sources disagree. The national handbook is explicit that roof rats range along the lower East Coast, through the Gulf States up into Arkansas and along the Pacific Coast, and states that most of the interior of the United States is free of roof rats, with isolated infestations usually stemming from infested cargo shipments. Texas A&M's own extension writing describes them as quite common in urban communities in East Texas and throughout the south.

One Texas reference is broader — a mammal survey describing the species as common over most of Texas, especially in towns — but it gives no regional or county breakdown, and we found no county-level record, survey or extension publication placing established populations in Lubbock, Amarillo, Midland, Odessa or the counties around them.

So here is the editorial position, stated plainly. We treat the Norway rat as the default commensal rat of this region. We describe the roof rat as the species associated with East Texas, the Gulf Coast and the South, which may turn up locally in a structure but which we cannot show is widely established here.

And then we let the property decide. Elevated droppings, runways along rafters, gnawing high in the structure and entry near the roofline point to a roof rat regardless of what a distribution map says. Burrows along foundations, activity at slab level and low-wall gnawing point to a Norway rat. The evidence on the job outranks the general case, in both directions.

One local habitat note worth having. The Texas mammal literature associates roof rats with cotton gins and the grain warehouses attached to them — which is the one genuinely Llano Estacado-relevant mention we found in a priority source, and worth knowing if your problem is in that kind of building rather than a house.

Norway rats work at grade. They are burrowers, with burrows found along building foundations, beneath rubbish and woodpiles. They dwell in basements and on ground floors, and the Texas literature places them in feed stores, chicken houses and dumps, with burrows under sidewalks and outbuildings. Nests are below-ground or at ground level, lined with shredded paper, cloth or other fibrous material.

They do still climb, and this catches people out. The same source notes Norway rats traversing telephone wires between buildings. Ground level is a strong preference, not a limit — so an attic problem is not automatically a roof rat.

Roof rats work aloft. They live and nest above ground in shrubs, trees and dense vegetation, and inside structures they favour enclosed elevated spaces — attics, wall voids, ceiling voids and cabinets. They enter mostly near the roofline, and on farms the Texas literature places them in attics, rafters and crossbeams.

Which means the trap placement rules are different. For Norway rats, traps go against walls in dark corners where droppings are, positioned at right angles to the wall with the trigger end nearly touching it. The reason is behavioural: AgriLife's rodent training describes rats as thigmophilic — touch-loving, travelling in contact with a surface — and negatively phototropic, avoiding light. A trap in the open middle of a floor is a trap in a place a rat has no intention of going.

For roof rats, traps go at ground level and aloft. Ledges, shelves, branches, fences, pipes and overhead beams. AgriLife's attic guidance is to place snap traps wherever you find droppings, usually along rafters or next to stored boxes.

And the sealing follows the same split. Norway rats: seal at grade — foundation gaps, slab edges, utility penetrations, door sweeps, garage door corners. Roof rats: seal at height — roofline, soffit and fascia junctions, vent and flashing gaps — and treat overhanging tree limbs as an access route to be cut back rather than as landscaping.

The documented list. The wildlife damage handbook names murine typhus, leptospirosis, trichinosis, salmonellosis and rat-bite fever for the Norway rat, with plague added for the roof rat. That is a real list and rats are worth keeping out of a building on those grounds alone.

Correction one: typhus is not a West Texas disease on the published evidence. Texas DSHS records more than 8,600 flea-borne typhus cases between 2008 and 2025, ranging from a low of 135 in 2010 to a high of 1,110 in 2025, with roughly 72 percent of cases hospitalised and seventeen deaths across the whole period. Those are serious numbers. But DSHS is specific about where they occur: most Texas cases are in South Texas from Nueces County southward to the Rio Grande Valley, with newer endemic areas around Dallas-Fort Worth, Houston, Bexar and Travis counties. West Texas is not identified as a focus.

Correction two: rats are not the hantavirus animal people mean. The hantavirus that causes pulmonary syndrome in the United States is spread by the deer mouse — we cover that on the house mouse page, and it matters here because this region carries a disproportionate share of Texas cases. There is a rat-associated hantavirus, Seoul virus, carried by Norway rats, but the CDC notes transmission to humans is rare. In a 2017 outbreak traced to pet rats, seventeen people showed evidence of recent infection, eight had a febrile illness, three were hospitalised and there were no deaths.

The structural case is usually the stronger one anyway. Rats gnaw wiring, with the potential to start a fire — that is stated plainly in the AgriLife material and it is the risk most likely to actually cost somebody. On agricultural property the other figure worth having is consumption and spoilage: each rat eats roughly twenty to forty pounds of feed a year and probably contaminates around ten times that amount.