The Norway or Brown rat is the most common species to be found in Oxfordshire and the home counties. It weighs between 350 and 500 grams and is typically between 200 and 270 mm long. Its fur can be various colours from almost black through to grey, however they are most commonly grey/brown. The tail is shorter than the combined length of the head and body. The ears and eyes are small relative to the length of the body.
Where they are found
The brown rat is widely distributed throughout both rural and urban areas and will rapidly colonise areas that offer both shelter and food. Damaged sewer systems provide an ideal habitat for rats which may give them with access to the home.
Rats are active burrowers, digging holes which extend far into the ground, sometimes in a complicated tunnel system with numerous openings. The burrows are multifunctional, serving as a place to rear young, to rest during the daytime (rats are typically nocturnal) and to escape from predators.
It is often the presence of holes in the ground (rodent workings) that provide the first indications that there is an active rodent infestation within an area.
Spread of disease
Rats are associated with the transmission of several diseases, Weil’s disease and salmonellosis in particular. Disease transmission occurs largely due to the close association between rats and human settlements. It is important to realise that in the absence of direct contact between humans and rats disease transmission is unlikely to occur.
Gnawing is part of the natural behaviour of rats, and may lead to significant damage to electrical cables, wooden fittings and lead pipes. Furthermore as a result of their burrowing rats may undermine foundations and cause damage to drainage systems.
Control of rats
It is widely believed that the rat population is increasing although there is no evidence to substantiate this. However it is important to realise that occupied areas provide an ideal environment for rats providing both shelter and food.
It is extremely important to ensure that all refuse is disposed of carefully. This particularly applies to foodstuffs although a pile of discarded timber or an unwanted piece of furniture can provide shelter for a colony of rats. Rats can be controlled a number of ways depending on the circumstances; rodenticide (poison baits) trapping, gassing with aluminium Phosphide, or by terrier dogs are the most common ways. Rodenticide should only be administered by profession pest controllers to eliminate the risk of secondary poisoning of non-target species and gassing can only be applied by those pest controllers who are authorised.
Signs of a rat problem
Rats are most active at night and usually hide from humans. The typical signs of a rat problem in the home are:
- Scratching noises - in walls or under the floor as rats scurry around
- Droppings - rats leave dark, tapered droppings about 10-14mm long
- Distinctive smell - rats leave an ammonia-like smell that will be particularly strong in enclosed areas such as under cupboards
- Damage - rats have teeth that grow continuously and gnaw on wood and plastic to keep them trim. Rats can even chew through electrical cables and pose a serious fire risk.
- Ripped food packaging - rats will tear open food and may leave teeth marks
- Nests - rats build nests in warm, hidden places using shredded material such as newspaper and fabrics. Nests will often contain young rats
- Burrows - In gardens, rats will dig burrows especially in compost heaps or under sheds. They will also build nests under garden decking