Rats. The word alone conjures up fears of scratching sounds coming from inside walls, filthy kitchens, and disease. The Norway rat, Rattus norvegicus, is a large, robust-bodied rodent that is considered the most important pest rat in Ontario and across much of the world. From nose to tip of the tail, which is short in relation to the body, this rat averages 40 cm long and weighs 340 grams. However, there have been Norway rats captured that have reached 48 cm long and 815 grams!

 

Fur ranges in color from reddish brown to dark gray and due to high variation, fur color is not a reliable way to tell one rat from another. Norway rats have small ears but have excellent sense of hearing, tasting, touch and smell, and although their eyes are prominent, Norway rats have a poor sense of sight and are color blind. Rats are what is called 'crepuscular' creatures, which means they are active around sunset and sunrise, but not during the day or the middle of the night. Norway rats are exceptional leapers, runners, swimmers, and are capable of climbing pipes, bricks and tree trunks.

 

Contrary to its name, the Norway rat is originally from eastern Asia but was readily spread by human movement over the last few centuries. The Norway rat is especially adept at living with humans and thrives in urban and rural settings. In fact, the way that a rat behaves is strongly tied to the type of environment in which it is living. This makes it difficult to describe rat behavior in a straightforward way. In general, Norway rats dig burrows into soil to use as safe havens and nesting sites. In a city, these rats exploit cracks, crevices, and holes in streets, sidewalks, and building foundations to use as burrows. Holes as small as 1 inch across may be enough to allow these rats to enter and exit burrows! Norway rats have a fast reproductive cycle; females can produce nearly 40 offspring per year over 4 litters.

 

Rodents transmit disease, damage property, and cause emotional distress; three important reasons why PMPs are called on to snuff out infestations. Managing rodent infestations is usually a combination of exclusion (sealing up places that allow rats to come in and out of a structure), limiting/removing food (omnivorous diets provide a lot of opportunity) and water (Norway rats must take water daily), trapping, and baiting. Thorough inspections are essential, look for capsule-shaped droppings (2-2.5 cm), evidence of gnawing and nesting, and even 'grease' trails that form in trafficked areas.