Norway Rat (Rattus norvegicus)

Identification

The Norway rat is a stocky, heavy-bodied rodent measuring 7–9.5 inches (body only) with a thick tail shorter than its body length. Adults weigh 10–17 ounces. Fur is coarse, brown to grayish-brown on the back with a lighter gray or white belly. Ears are small relative to the head and do not reach the eyes when folded forward. The blunt nose distinguishes it from the more pointed roof rat.

Norway rats produce droppings that are capsule-shaped, approximately ¾ inch long with blunt ends — noticeably larger and thicker than mouse droppings or roof rat droppings.

Behavior and Habitat in Brownsville

Norway rats are ground-dwellers. In Brownsville, they burrow along foundation walls, under concrete slabs, beside garbage dumpsters, and in landscaped beds with dense ground cover. They are strong swimmers and thrive near the irrigation canals and resaca banks that cross through the city. Pressure is heaviest in San Benito, where the Resaca de los Fresnos runs right through residential neighborhoods.

Unlike roof rats that climb, Norway rats travel at ground level along walls, fences, and utility corridors. They are nocturnal and cautious — a Norway rat may take several days to approach a new trap or bait station. This wariness, called neophobia, makes DIY trapping slow and frustrating, which is where professional rodent control earns its keep.

Signs of Infestation

Greasy rub marks (dark smears) along baseboards and wall edges where rats travel the same path nightly. Burrow holes 2–3 inches in diameter along the foundation, under A/C pads, or beside porch steps. Gnaw marks on wood, plastic, and even soft metal — Norway rats must gnaw continuously to control incisor growth. Scattered capsule-shaped droppings in cabinets, pantries, and along wall-floor junctions.

Health Risks

Norway rats carry leptospirosis (transmitted through urine-contaminated water), salmonellosis, rat-bite fever, and can host fleas that carry murine typhus — a disease with documented cases in South Texas. Their droppings and urine contaminate food storage and preparation surfaces. Gnawing on electrical wiring creates fire risk inside wall cavities.