The Norway rat is the hardest rodent to get rid of, primarily because of its size, intelligence, and extreme neophobia — a deep-wired suspicion of anything new in its environment, including bait and traps.
Norway rats are burrowing animals that establish well-defended underground colonies, often outdoors near foundations, woodpiles, or drainage. They can reach 11–17 inches in body length and require a significantly higher bait dose than roof rats or mice. Their neophobia means they may avoid new bait placements for 1–3 days before feeding, and a single inadequate placement is almost never enough — the colony simply works around it. Multi-day, consistent bait access is non-negotiable against Norway rats.
- Norway rat lethal bait dose with RatX: 40–60 grams (1½–2 oz), consumed over multiple feedings across 3–5 days.
- Norway rats exhibit neophobia for 1–3 days after a new bait or trap is introduced to their territory.
- Norway rat colonies burrow underground, meaning most deaths occur out of sight in tunnels — not in open areas.
- Norway rats can weigh up to 500 grams — roughly 10x the body weight of a house mouse — requiring proportionally higher bait volume per infestation.