There are two rat species in the United States that are considered common home-invading pests. These species are commonly known as Norway rats (Rattus norvegicus) and black rats (Rattus rattus). Due to intense competition between closely related species, Norway rats always outcompete black rats for resources, which makes the former the dominant rat species in urban and suburban areas throughout the US. Norway rats weigh around one pound, and they are generally reddish-brown with whitish-grey bellies, but black Norway rats can be found in some areas of the US. Norway rats first arrived in the US on colonial ships sometime around 1775, and today they can be found in all 48 states in the contiguous US. These rodent pests have adapted to live alongside humans, and they are commonly found within cellars, basements, garages, sheds, crawl spaces, wall voids, and they frequently burrow beneath concrete slabs and against housing foundations in residential areas. Norway rats generally inhabit the lowest levels in structures, but these filthy pests are also known for thriving in garbage dumps and sewers where they are able to find the food and water they need to survive.

While Norway rats will eat just about anything, they prefer to consume nutrient-rich fresh foods, as opposed to stale and contaminated foods. Norway rats favor cereals, meats, fish, nuts and certain fruits and they require a half ounce to 1 ounce of water daily, but they receive much of their water by consuming moist foods. Surprisingly, Norway rats are able to meet their nutrient and water requirements by feeding on garbage within residential dumpsters and trash bins. These rodent pests possess a taste-sense that allows them to detect contaminant levels in food as low as .5 parts per million, which may partly explain why Norway rats often avoid poison baits. Their reluctance to consume bait is known as “poison shyness,” and they often taste baits before chowing down solely to detect small amounts of dangerous toxins. Norway rats are also wary about consuming novel food sources that appear too convenient to be true, making them neophobic (fear of anything new) concerning bait. Some scientific evidence suggests that certain rat populations, notably urban rats, are more neophobic of baits than other rat populations. Luckily, however, the neophobic behavior that rats demonstrate when confronted with bait wears off in time, sometimes within a 24 hour period. That being said, it is not uncommon for Norway rats to completely ignore baits, especially when alternative food sources are available and easily accessible.

Have you ever used a bait that a rat proceeded to ignore indefinitely?