Rat facts

Domestic rats make wonderful pets, but their wild counterparts are often not so welcome. Learn the truth about wild rats with these facts.

How do I identify a rat?

The best known rat in the UK is the Norwegian or brown rat, Rattus norvegicus. The black or ship rat, Rattus rattus, is now rare in the UK.

A wild rat's fur is usually brown, grey, or less commonly black. An unusually coloured rat might be an escaped or abandoned pet, in which case a call to a local vet or rat rescue is a good idea.

Brown rats can measure up 25 centimetres, not including the tail. Males are generally larger than females, with average weights of 550 grams and 335 grams respectively. Stories of rats as big as cats are exaggerations!

Where do rats live?

Rats mainly exist in close contact with humans.

They generally move to buildings in autumn and winter for shelter and food; they're often found in warehouses, farms and roof spaces of houses. In summer they return to the open countryside to feed on growing vegetation. They also inhabit undisturbed storage areas such as haystacks and tyre heaps or pallets, especially if these areas are close to food.

If food is available all year round, rats will attempt to stay on site permanently.

Outside, their favourite haunts are:

  • Under wood piles or lumber that is not being used often
  • Under bushes and vines and in tall thick grass
  • In appliances and old furniture that has been left outside and is not being used
  • In and around rubbish that has been left out
  • In holes or gaps under buildings

Once inside, they will happily live:

  • Inside the insulation of walls or ceilings
  • In or behind cupboards, counters and bathtubs
  • Near the boiler
  • In basements or attics where things like cardboard and cloth are stored

What do rats eat?

Brown rats favour cereal, but being true omnivores they are known to eat almost anything. On average, a rat will consume 25-30 grams of food and drink approximately 60 millilitres of water per day.

When in the house rats will eat anything not sealed in an air-tight container, and even that is no guarantee. Rats have exceptionally powerful jaws and can eat most food stored in paper, plastic or cardboard containers.

What attracts rats?

Rats will come indoors searching for a cosy place to nest and a good supply food. Common favourites are:

  • Uncollected rubbish and litter
  • Food for pets and birds that has been left out and not eaten
  • Fruits and berries that have fallen to the ground
  • Untended compost heaps
  • Dog droppings
  • Discarded food

How do I know if I have a rat problem?

You will know that you've got a rat problem when you find or hear:

  • Droppings (typically 12 millimetres long)
  • Scratching noises
  • Evidence of gnawing
  • Burrows or nests

Are rats harmful?

If they enter into the home wild rats may carry parasites and diseases that are harmful to humans and animals, including:

  • Leptospirosis (Weil's disease, which can be fatal to humans)
  • Ringworm

Brown rats do not carry the plague

Wild rats are more likely to try to escape than bite, so never try to approach one in a tight spot. A rat can inflict a lot of damage with its powerful jaws and sharp incisors. If you do get bitten then seek immediate medical advice, and be aware that you may need an injection against tetanus.

Another significant problem is the structural damage rats can cause from their gnawing and burrowing activities. This ranges from minor holes in walls/doors/furniture/cupboards to structural collapse, flooding, electrical faults and fire (due to gnawing through cables).

Things you might not know about rats

  • Rats are not incontinent, but they do scent-mark pathways and territories.
  • A rat's teeth grow continuously, and are worn down by gnawing on hard surfaces and by working them against each other (known as bruxing).
  • Rats are crepuscular, meaning that they are most active at twilight (dawn and dusk), although they can sometimes be seen during the day.
  • They are active burrowers (although older male rats will generally not burrow), good climbers and reasonably good swimmers (often leading to confusion with water voles).
  • They have poor eyesight and are colour blind, but have acute hearing and a good sense of smell and taste.
  • Rats are capable of reproducing at six weeks old, and can have up to five litters per year if conditions are suitable. The litter size can range from 6-14 young.
  • The average lifespan of a wild rat is less than a year.

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