Rodent Control: Mice & Rats

Common Rodents in St. Louis

Mice and rats are year-round problems in the St. Louis metro area, but they become especially aggressive invaders in fall and winter when they seek shelter, warmth, and food inside homes. A single mouse can squeeze through a gap the size of a dime, and once inside, it starts reproducing immediately — a single pair of mice can produce up to 60 offspring in a year. Rodents contaminate food, chew electrical wiring (a leading cause of house fires), and carry diseases including hantavirus and salmonella.

House Mouse

The most common rodent invader in the St. Louis area. Small (2-4 inches), gray or brown, with large ears relative to their body. They nest in wall voids, attic insulation, under appliances, and in storage areas. Extremely curious and will explore new objects in their environment quickly.

Norway Rat

Large (7-10 inches body length), heavy-bodied rats with blunt noses and small ears. They burrow along foundations, under concrete slabs, and in crawl spaces. They are cautious and neophobic (afraid of new objects), which makes them harder to trap than mice.

Roof Rat

Slightly smaller and more agile than Norway rats, with larger ears and a longer tail. Excellent climbers that prefer to nest in attics, soffits, and upper levels of structures. Less common in Jefferson County than Norway rats, but present in the St. Louis metro.

Signs of Rodent Activity

• Droppings along baseboards, in cabinets, under sinks, or in pantry areas — mouse droppings are rice-sized; rat droppings are 1/2 to 3/4 inch
• Gnaw marks on food packaging, wood, or electrical wiring
• Scratching or scurrying sounds in walls, ceilings, or attics — especially at night
• Grease marks (rub marks) along walls and baseboards where rodents travel repeatedly
• Nesting material — shredded paper, insulation, or fabric found in hidden areas
• A musky odor, especially in enclosed spaces like cabinets or closets

How Roberts Controls Rodents

Every R.O.S. (Regular Outside Service) account includes 3 exterior rodent bait stations (ERBS) at no additional charge. These tamper-resistant stations are placed along your foundation and maintained at every bi-monthly service visit.

Exterior Bait Stations (ERBS)

For routine maintenance, we use professional-grade rodenticide bait. For heavy rodent pressure or active infestations, we switch to a fast-acting cleanout bait — a non-anticoagulant product with a stop-feed mechanism that leaves more bait available for the rest of the population.

Interior Trapping

For rodents that have already gotten inside, we use strategic snap trap placement in areas of confirmed activity. Interior trapping removes the animal immediately, unlike bait which takes time.

Entry Point Exclusion

Baiting without exclusion is just feeding a revolving door of rodents. We identify and seal gaps as small as 1/4 inch where mice enter — using steel wool backed by caulk for small gaps, and hardware cloth or metal flashing for larger openings.

Rodent protection is built into our R.O.S. program — it is not an upsell. Learn more about R.O.S. →

Prevention Tips

• Seal all exterior gaps larger than 1/4 inch — use steel wool + caulk for small gaps, hardware cloth or metal flashing for larger openings.
• Keep garage doors closed and install door sweeps on all exterior doors.
• Store food properly — sealed hard-sided containers, not bags. This includes pet food and birdseed.
• Eliminate clutter in basements, garages, and storage areas that provides nesting habitat.
• Trim tree branches back at least 6 feet from the roofline to prevent roof rat access.
• Manage trash — Keep cans sealed and remove fallen fruit from the yard.