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Rats

Introduced rodents that live alongside people, nest in roofs, walls and gardens and gnaw through building materials and wiring. Roof rats are the most common household rat in many Australian cities.

Written by PestMan Editorial TeamTechnical review pendingPublished Updated
Common species
Roof rat, Norway rat
Gap size
About 12–15 mm for young rats
Peak indoors
Autumn and winter
Health relevance
Leptospirosis, rat lungworm, wiring damage
Risk level
High

Rat identification

How to recognise rats

  • Adults are much larger than mice: body roughly 15–25 cm plus tail.
  • Roof rat: slender, pointed snout, large ears, tail longer than head and body.
  • Norway rat: heavy-set, blunt snout, small ears, tail shorter than head and body.
  • Droppings: roughly 10–20 mm long, much larger than mouse droppings.

Common species in Australia

Roof Rat (Black Rat)

Rattus rattus

An agile climbing rat that nests in roof voids, trees and dense vegetation. The rat most often heard in ceilings in Brisbane and other coastal cities.

Norway Rat (Brown Rat)

Rattus norvegicus

A large, heavy-set burrowing rat found around drains, creeks, sheds and under slabs. Less of a climber than the roof rat.

Rat overview

The two household rats in Australia are the roof rat (black rat, Rattus rattus) and the Norway rat (brown rat, Rattus norvegicus). Both were introduced. Native rodents such as bush rats rarely enter homes.

Roof rats are agile climbers that travel along fences, power lines and tree branches into roof voids. Norway rats are heavier burrowers found around drains, creeks, sheds and under slabs.

If you are unsure whether you have rats or mice, see how to tell a rat from a mouse.

Behaviour

  • Mostly active at night; scurrying and gnawing noises in ceilings are a common first sign.
  • Cautious of new objects, so traps and bait stations may be avoided for several days.
  • Travel the same routes repeatedly, leaving greasy rub marks along beams and walls.

Habitat

  • Roof voids, wall cavities, sheds and dense vegetation such as palms, bamboo and vines (roof rats).
  • Burrows under slabs, along creek banks, in compost heaps and around drains (Norway rats).

Lifecycle

  • Females can breed from a few months old and produce several litters a year of roughly 5–10 pups.
  • Under good conditions a small population can grow quickly, especially in warm months with abundant food.

Food sources

  • Fallen fruit, nuts and seeds, bird seed and pet food.
  • Rubbish, compost and food scraps.
  • Water from pools, ponds, pet bowls and leaking pipes.

Entry points

  • Gaps under roof sheeting, around gutters and under ridge capping.
  • Openings around pipes, air-conditioning lines and vents.
  • Overhanging branches, vines and power lines touching the roof.
  • Gaps as small as roughly 12–15 mm can admit a young rat.

Infestation signs

  • Scratching or running noises at night.
  • Droppings along routes, in roof voids and cupboards.
  • Gnawed wiring, pipes, food packaging or fruit.
  • Greasy rub marks and nests of shredded material.

Health implications

  • Rats can spread diseases such as leptospirosis and salmonellosis through urine and droppings.
  • In Queensland and NSW, rats carry rat lungworm, which can infect people and dogs through slugs and snails.
  • Gnawed electrical wiring can create a fire risk.

Prevention

  • Remove food: pick up fallen fruit, store pet food and bird seed in sealed containers, use rodent-proof compost bins.
  • Cut back branches and vines at least a metre from the roof.
  • Seal entry gaps with rodent-resistant materials such as steel mesh or metal flashing.
  • Reduce clutter in sheds, under houses and against fences.

Treatment overview

  • Effective control combines exclusion (sealing entry points), sanitation and trapping or baiting.
  • Rodenticides must be used exactly as labelled in tamper-resistant bait stations to reduce risks to children, pets and wildlife such as owls.
  • Dead rodents in wall or roof voids can cause odour problems, which is one reason trapping and exclusion are often preferred.
Product safety

If you use any pest product, read the label first and follow it exactly — it is a legal requirement in Australia. Keep products away from children, pets and food areas as the label directs.

Questions about rats

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Mice

Small, curious rodents that squeeze through tiny gaps, nest in walls, cupboards and appliances and breed quickly. The introduced house mouse causes most household problems.

Cockroaches

Fast, flat-bodied insects that hide in warm, damp gaps and come out at night to feed. A few introduced species cause most household problems in Australia.

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Sources & further reading

PestMan provides general information only and does not replace licensed pest-management, medical, veterinary or structural advice. Always read and follow product labels. Read our disclaimer.