NORWAY & BLACK RATS (Rattus norvegicus & rattus)
FOUND IN BC? Yes. Rats are widespread in the Lower Mainland, coastal islands, and interior. They are present in the Okanagan Valley, Kamloops, the Shuswap, Revelstoke, and the Kootenays.
Identification
Rats were introduced to BC in the mid 1800s, and there are two species causing problems to humans: Norway and Black rats. These species can be differentiated by physical characteristics and droppings.
Norway Rats
The larger of the two species, Norway rats have a stocky body roughly 21 centimetres long, with a tail that is shorter than the length of the head and body combined. These rats measure 30 to 45 centimetres from snout to tip of tail. They have small ears, a blunt snout, and are grey to black in colour. Droppings from a Norway rat are long with rounded ends.
Black Rats
Black rats, or roof rats, have a smaller body measuring about 17.5 centimetres long. Their tail is longer than the length of head and body combined, and they are more slender than a Norway rat. Black rats measure 33 to 43 centimetres from snout to tip of tail. They have large ears, a pointed snout, and grey to brown colouring. Black rat droppings are long with pointed ends.
House Mouse and Bushytailed Woodrat
Norway and Black rats are more likely to be confused with one another, as the house mouse is much smaller and rounder than either rat. Native to BC, the Bushytailed Woodrat has a long, bushy tail which sets it apart from the house mouse and rat species.
Bushy-tailed wood rat (Neotoma cinerea), Weber County, Utah. These animals are enamored of shiny objects and will drop whatever they are carrying in favor of a coin or spoon.
Bushytailed Wood rat – photo sourced from: https://www.sciencephoto.com/media/385655/view/bushy-tailed-woodrat
Roof Rat
Black rat, Rattus rattus.
Norway Rat
Pictures sources from: https://hawxpestcontrol.com/roof-rats-versus-norway-rats-which-are-invading-your-home/
Once established, rat populations can rapidly increase as females are capable of producing several litters per year, and can reproduce year round. In favourable conditions a pair of rats breeding could produce over 900 offspring in one year.
Ecology
Norway rats prefer moist semi aquatic environments, as they are strong swimmers. Often they can be found in sewer systems, and ground level in buildings where they can build extensive tunnel systems. Black rats are good climbers, and often nest high in ceilings or attics in buildings. They also can be found in forested environments in milder climates. Both rat species can invade a wide variety of habitats as they are opportunist and adaptable feeders.
Introduction and Spread
These rats are invasive in BC. The Norway rat is native to China and Mongolia, and the Black rat is native to India. They were introduced through European settler ships coming to Canada in the mid 1800s, and can now be found worldwide anywhere inhabited by humans. The more development and buildings that are created by humans, the more shelter and food resources are available to help the spread and growth of rat populations.
Impacts
Rats damage infrastructure, contaminate food sources, and predate on seabird populations. Once in a building, rats cause damage by chewing through insulation, walls, metal, and wires, which can start electrical fires. Rats are known to carry and spread diseases. By eating food inside homes and buildings, rats contaminate human food sources. They also have negative impacts on crops and small livestock by preying on chicken eggs and chicks. Rats contribute to the decline in seabird populations along the coast by eating chicks, eggs, and even adult birds.
What Can We Do?
Sourced from: https://www2.gov.bc.ca/assets/gov/environment/pesticides-and-pest-management/managing-pests/imgs/wildlife_poisoning_lg.jpg
There are several actions you can take to help prevent rats from spreading further and entering your home. Firstly, do not release or transport rats in BC – they are invasive and have negative impacts on human well being. Once you notice signs of rat activity in your house, block off potential points of entry, remove any food or garbage that might attract the rats, and choose a proper control method. Possible entry points for rats might be small cracks and holes (rats only need a quarter sized opening to fit through) either in the foundation, outside walls, or roof. Check for areas where rats might have a food or water source, or where vegetation touches the building and creates a pathway for entry. Choosing a proper control method is best done with the help of a licensed professional who can recommend the best long term solution. There are several ways to control rats, including traps, rodenticide (poison), ultrasonic repellents, and predators. When possible, choose a rodenticide alternative, as poisons can harm pets, wildlife, and humans. Rodenticide is highly toxic, but does not kill the rat immediately and can therefore enter the food chain if it is captured by a predator shortly after ingesting the poison.
References
https://www.richmond.ca/services/climate/environment/invasivespecies.htm