The Norway rat, also known as common rat and brown rat, is a vermin introduced in Britain in the early 18th century. The average specimen reaches up to 18 inches (45 cm), total length, although there have been reports of 27 inches (70 cm) Norwegian rats. It has a blunt nose with small eyes and ears.
The Norway rat has a coarse, thick fur, usually black, grey or brown in colour. The underbelly of the rat is in lighter grey or brown. The tail is not covered in fur but in scaled skin. The average adult Norway rat weights 350g. Although there are frequent reports of one-metre-long Norway rats, they are either an exaggeration, or other species of rodents.
Albeit its name, Norway Rat does not originate from Norway. It was introduced in the Nordic country after the name Rattus Norvegicus was already popularised. Scientists speculate Norway rats originate somewhere in China or Eastern Mongolia. During the Middle Ages, they spread to other parts of the world.
The Norway rat is cosmopolitan and lives on every continent. Antarctica was declared rat-free in 2012, when the population of Norway rats on Rat island was eradicated. They were introduced to the island after a Japanese ship wrecked nearby. There are several other rat-free zones in the World—namely Iceland and Alberta, Canada.
As an omnivore, the Norway rat has a rich diet. It consists of, but is not limited to, cereals, seeds, grains, nuts, meat, pet food, eggs, dairy products, and even chocolate. There are just a few foods they avoid—raw beets, raw celery, and peaches. Rats get their food from both outdoors and indoors locations.
Urban tales of rats preying on cats and dogs are exaggerated. Although they are omnivores, they are not keen on hunting. Rats are scavengers and will attack only when starving. However, it is not unlikely for a rat to attack and potentially kill a dog or a cat in self-defence.
- Rats are social animals and live in colonies. A wild rat colony can number in the hundreds. It is rare for Norway rats to nest indoors. They prefer underground burrows from where they enter buildings in search of food, for instance your garage.
- They are nocturnal and rarely go outside in daytime. Unlike what the majority of people believe, they are not aggressive and prefer to shy away rather than engage in a battle. Yet when threatened, they become vicious fighters.
- Rats reproduce rapidly. A rat litter consists of up to 24 pups. Their pregnancy is just 28 days long.
- The Norway rat can jump up to 70cm and can swim over long distances.
- They have an acute smell and hearing which allows them to sense any disturbance. However, they are colour-blind and have poor vision.
Rats are well-known disease vectors and carry numerous infectious pathogens. The list includes serious illnesses such as typhus, Weil’s disease, rat bite fever, Q fever and leptospirosis. They contaminate food and water sources with saliva, droppings and urine.
The disease most commonly associated with rats—plague—is not carried by Norway rats. It is transmitted by fleas leaving an infected black rat and attacking man. Black rats are now extinct in the UK but can be found throughout Europe. They were driven out of Britain by the Norway rat. Black rats also spread Hantaviruses.
However rats are one of the few mammals not known to spread rabies. Although there are incidental reports of rats infected by the disease, there are no known cases of rat-to-human rabies infection. Rats are also extremely resistant to the rabies virus.
Norway rats cause huge harm to world economy. They cause structural damage to building and can cause a fire by chewing on a cable. They can also destroy flood defences, bridges and security fences.
Rats feed on wheat and rye. Tons of harvest are destroyed each year due to disease contamination, caused by them. They also infect domesticated animals.
- Chewed items – Like mice, rats have incisors which never stop growing. Thus they need to chew onto something hard on a regular basis – cables, woods, even pipes.
- Droppings – the shape and size of black olives. Unlike mice, rats are a bit more protective, so they have better hiding skills and don’t want to be noticed. If you hear noises, see chewed cables, but don’t find droppings, it’s probably rats, not mice.
- Smears – rats have poor sight, that’s why they follow the same routes while moving. Constant moving on the same tracks will leave dark marks on surfaces – that’s called smears.
- Noises – rats can climb walls, so you might hear scratching noises behind walls.
- Footprints – you might see footprints on dusty places (basements, attics). Like any other animal, rats leave their prints.
How to deal with rats inside your home
Rat control must focus not only on exterminating the population but on preventing the re-entry of rodents inside your property. There are several different methods of rats control.
1. Poison is the most effective at killing rats.
2. With traps there is no risk of dead rats in hidden locations. In order for a trap to be effective, it must be placed on the path of the rats.
3. Another important aspect of rat control is preventing their future access. All points of entry must be sealed to avoid re-infestation. These includes holes in the walls and attic, gutters, pipes, structural gaps, and even roof tile intersections.