Norway rat

3 Things You Might Not Know About the Norway Rat

Norway rats have been around for millions of years. As pest management professionals, you are knowledgeable on their biology, behavior, and treatment. There is always more to learn. Here are three things you might not know about Norway rats.

Rodent Infestation


They live in family groups. These groups can be fairly large. One study found Norway rat colonies that numbered more than 150 individuals in a burrow system. Because of these large numbers, some burrow systems can be quite large and complex. There are different areas for individuals, nursing/weaning females, and food caches. When you catch a Norway rat, the issue could be, and probably is, a lot larger than that one individual rat. Inspect for burrow openings and remember that there are likely multiple openings. Increase the number of traps and stations in that area to capture and monitor the situation. Catching one rat is an indication of a larger issue. Carefully consider the conditions around the capture and how to mitigate those to reduce the site’s attractiveness and reduce the surrounding rat populations.


They outcompete roof rats. Roof rats arrived in North America before Norway rats and were already well established in most areas. When Norway rats came on the first ships from Europe, they started getting settled. Norway rats breed slightly faster with more pups per litter. They were better at foraging and finding habitat. Eventually, roof rats got pushed out and now are in the southern portions of the US and around coastal cities. For a long time, the conventional wisdom was that you would have Norway rats or roof rats, not both. New conditions and new research has shown that the two populations are mixing and living in the same areas. As long as there is enough food to support both species, they can have healthy populations in the same small areas. Even house mice are getting into the mix and are found near populations of rats. The limiting factor is food. Without an ample food supply, they won’t all be able to survive. If food conditions become especially sparse, Norway rats will even cannibalize each other.

Norway rat
Norway rat bait Station


Rats use tools. Rats are smart and will take advantage of their surroundings to get what they need (food, water, and shelter). Numerous lab studies have shown their ability to use tools to get food. They learn quickly and, over time can become more adept and faster at using their tools. One ingenious study cites scientists who taught rats to drive a little plastic car to get a treat. Rats have also been shown to help each other, even when it doesn’t directly benefit them. While these have been mostly laboratory studies, this directly translates to Norway rat behavior in the wild. Their social behavior and learning capacity have made them well-adapted to getting the resources they need while avoiding control methods.

Outsmarting the rats is challenging but not impossible. They want to hide (with their 149 family members) and can live near other rodents (roof rats and house mice), and they are smart. You can be smarter by understanding them and putting the best rodent bait stations in the right places to manage their populations. For more on the best rat bait stations, snap traps, and other professional pest control products to use, click here!

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