Keeping rats and mice under control

Rats and mice can spread diseases that can infect both people and pets, including:

• salmonellosis
• campylobacteriosis
• leptospirosis
• tularemia

These diseases can be passed on by:

• direct contact such as bites
• unsafe handling and disposal of infected dead rats
• eating food or drinking water contaminated with:
  • rat urine
  • faeces
  • saliva
  • hair
• breathing dust contaminated with the urine and faeces of infected rats

Diseases can also be transferred by ticks, fleas, and mites that live on infected rats.

Rodents can also damage building structures by:

• gnawing through lead and aluminium sheeting
• chewing through electrical wiring, which can start fires by shorting-out appliances or lighting fixtures.

The common rodents to WA include:

• the Black Rat (Rattus rattus)
• Brown Rat (Rattus norvegicus)
• House Mouse (Mus musculus).

Rats

Grey, brown or black in colour and larger than mice, reaching up to 25cm in body length and 400g in weight.

Mice

White, grey, brown or black and much smaller than rats. They reach up to 10cm in body length and are generally no more than 30g in weight.

Rats and mice normally come out at night so you may not always see them.

Signs you may have an infestation include:

• black, thin droppings (12 mm to 18 mm long)
• squeaking, gnawing or scratching noises in walls, cupboards, ceilings and under floors (these noises may also be a possum)
• debris / waste such as snail shells or fruits with the sides eaten out
• bones left in the corners of sheds, under homes and other secluded spots
• greasy trails or rub marks along paths they travel, especially supports or beams
• burrow holes around buildings
• signs of gnawing damage on wood, electrical cables or other building structures
• food left for pets that has gone missing
• pet dogs, cats and birds being more excitable than usual

Rats and mice are commonly found:

• in walls, ceilings and under floors
• behind or under cupboards or bathtubs
• behind boxes, machinery and furniture  
• in rubbish heaps, wood piles, thick vegetation, animal enclosures, paper or cloth
• in holes under buildings
• in sheds and garages.

Rats and mice can be controlled by taking away their source of food and shelter.

Food

• Ensure food is secured in sealed containers.
• Dispose of food scraps promptly and clean food preparation areas thoroughly.
• Block access points to food cupboard.
• Throw away any food or drinks that may have come into contact with rodents.

 Rubbish

• Ensure rubbish bins have tight fitting lids and are regularly emptied.
• Keep your property clear of rubbish.

 Building

• Check for and secure any potential entry points into the building like sealing gaps / holes and repairing or fitting mesh screens.
• Clear unused materials or clutter from around the property to reduce shelter / harbourage areas.

Gardens

• Regularly pick any homegrown fruit or vegetables and discard any fruit that has dropped on the ground or is rotting on trees.
• Cover vegetable gardens with netting and/or remove rotting vegetables regularly.
• Store firewood about 40cm above the ground to prevent hiding or nesting.
• Regularly remove garden waste or other disused material around your yard.
• Regularly clean out sheds and storage areas.
• Do not use open compost. Maintain compost bins and do not include meat scraps in compost.

Rainwater

• Cover rainwater tank openings and floor vents with wire mesh no coarser than 1mm and check and maintain these regularly.

Pets

• Keep pet food dishes clean and store bulk pet food supplies in containers and locations where rodents cannot enter or chew through.
• Feed pets smaller amounts more frequently and remove left over food. Consider low-waste or rodent proof feeders for backyard hens or aviary birds.
• Store bird seed and chicken feed in an airtight container.

Traps can be purchased from hardware stores or supermarkets.

The spring back-break trap is still the safest trap for home use but a plastic capture box may also be used.

Tips for setting a trap:

• Several traps should be used at one time.
• Do not set traps near food preparation areas.
• Place across ’runways’ for a few days before setting to allow rodents to get used to the traps.
• Traps can be successfully set with bacon, peanut butter, fish, meat, bread or chocolate.
• Check traps daily; remove any dead rodents and refresh the bait.
• Use an insecticidal surface spray around the immediate area to kill any fleas which may leave a trapped rodent’s body.

Poison baits are the most successful way to kill rodents. Many brands are available in retail shops. Some local governments supply poison baits free of charge to ratepayers.

Always read and follow safety directions and the instructions carefully and make sure children and pets cannot reach them.

Check baits regularly and replace them if they have been eaten. If you are dealing with a large rat or mice problem you may initially need to check and replace baits daily. A rat can eat a whole box of rat bait in one night.

You can also employ a pest management technician to treat your property with baits.

Things to consider

Chemical control may not be appropriate in all situations. Before using poison, consider the following:

• if rodents die and decay in hard to reach places they may cause an offensive odour
• pets and children may eat toxic baits or poisoned rodent bodies
• some individuals are sensitive to rodent control chemicals in their environment
• baits licensed for agricultural use must never be used for domestic purposes as they may release toxic gases.

Do not place baits in areas that pets can access easily. Some baits can be placed in pet proof containers to avoid accidental poisoning.

Consider restricting access to the area using a barrier or use a muzzle to reduce the risk of accidental poisoning.

Contact your vet if animals consume poisoned rodents or rodenticides.

When seeking the services of a pest management technician you should ensure:

• they are a licenced technician and registered pest management business who has endorsement for “commercial/domestic pests” which allows the technician to apply rodent baits.
• the technician should outline a treatment plan which includes assessment of the entry points, nest locations, waste containment, removal of food sources etc along with the pesticide selection.
• the technician should outline precautions or limitations of pesticides and how to dispose of deceased rodents.
• if the infestation continues, the pest technician should provide additional options, a different product may need to be used as rodents can drop off from eating one type of bait after a time.

Refer to guide to selecting a pest management business to help you to employ a licensed professional.

Before you start

• Wear disposable gloves, waterproof protective clothing and closed footwear.
• It is recommended you wear a face mask.
• Cover cuts and abrasions with a waterproof dressing.
• Check the product label of rodenticides for any additional specific disposal requirements or personal protective equipment (PPE).

Disposing of rodents

• Place dead rodent carcases into sealed bag or wrap in newspaper before placing in the green bin followed by washing hands thoroughly with soap.

Clean up

• Ideally, any cleaning should be undertaken by household members who are well and do not have a weak immune system.
• Regularly clean and disinfect areas where rats or mice have been in contact with – remove rodent droppings, mop floors and clean surfaces with disinfectant.
• It is recommended you wear a face mask when cleaning, particularly if sweeping up droppings or scrubbing.
• Wash bedding and any affected clothing with laundry detergent in hot water.

Wash your hands

• Wash hands with soap and dry your hands after completing the clean-up, and especially before eating.
• Change clothes after contact with rodents or their droppings/urine.

Tank inlets and overflows should have screens installed to prevent entry of mice and other small animals and leaves. Check the tank regularly to ensure there are no gaps.

If your rainwater tank has been contaminated, refer to rain water tanks on your property.

• Immediately clean the wound with soap and water.
• Dry the area, apply antiseptic cream and a clean bandage.
• Seek medical attention. You may need a tetanus immunisation, and in some circumstances (not always), antibiotics are given to prevent infection.
• As the wound heals, keep an eye out for signs of infection such as skin that is warm to the touch, redness or pain. Seek health care if these signs develop.

Talk to your neighbour about the rodents on your property as they may have the same problem. Rats or mice may also be breeding on their property and may be the source of the rat problem.

Property owners and tenants are required under the Health Miscellaneous Provision Act 1911 to prevent rodents harbouring (living) on their property.

If you cannot find out where the rodents are coming from report to your local government environmental health officer (external site) who may be able to assist with educating people in the local area.

Sometimes mouse plagues can occur in rural Western Australia. This is when there is a significant increase in a mouse population reaching plague proportions. This can lead to widespread infestations and cause extensive damage to crops and infrastructure. Factors such as floods or good rainfall can create ideal breeding conditions for mice.

Such plagues may occur in regional farming areas. The Department of Primary Industries and Regional Development (external site) assists the agricultural industries in such events.