Feral rats and mice are very adaptable public health pests. They are not fussy eaters and can make themselves at home in houses, sheds, garages and gardens. As well as causing unpleasant odours and damage to property and possessions, feral rodents can also pose a risk to human health.
Why the concern?
Introduced rodents can:
Carry diseases such as leptospirosis and typhus fever.
Contaminate food with their hair, droppings and urine, resulting in food poisoning and spoilage.
Generate unpleasant odours.
Carry fleas or ticks which can harm pets or humans.
Damage materials such as food containers, wood, particle board, insulation and wiring through gnawing.
Types of rodents
Native Australian rodents (for example Hopping Mice) pose little or no threat to public health and should be left alone as they are protected species. However introduced rodents may infest residential and agricultural areas and carry disease. The common feral rodents in SA are:
the Black Rat (Rattus rattus)
Brown Rat (Rattus norvegicus)
House Mouse (Mus musculus).
These pests will eat rubbish, pet food, food scraps, composts, fallen fruit and nuts, bird seed and dog faeces. Rats will travel up to several house blocks to find water and food.
Grey, brown or black in colour and larger than mice, reaching up to 25cm in body length and 400g in weight.
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.
Where they live
Rats and mice will shelter and nest in places such as homes, sheds, garages and gardens, particularly:
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.
Recognising rodent activity
Rodents are generally more active at night and are more common in late summer/early autumn. If you see rats or mice during the day, this usually indicates high numbers or that there is a good food supply nearby.
When inspecting for rat and mouse activity, look for:
Black, moist, thin droppings.
Debris left from rodents gnawing items like snail shells, almond shells and chop bones.
Food left for pets which has gone missing.
Signs of gnawing damage on fruit, and vegetables or materials such as wood, insulation and electrical cabling.
‘Runways’ which have formed when rodents have used the same path such as through vegetation/gardens or along fences.
Greasy rub marks on walls or skirting boards where rodents travel regularly.
Burrow holes close to sheds or under debris.
Avoiding rodent problems
Rodents are well adapted to living in human environments. To reduce their numbers on your property:
Dispose of food scraps promptly and clean food preparation areas thoroughly.
Inspect living and working areas for potential rodent entrances and block them where possible with concrete, hard setting filler, steel wool or heavy gauge sheet metal.
Ensure rubbish bins have tight-fitting lids and are regularly emptied.
Keep your home and property clear of rubbish.
Keep stacked materials such as wood and bricks at least 30cm above the ground to minimise hiding / nesting / thoroughfare of rats and mice.
Regularly clean out sheds, storage areas and dispose of unwanted items.
Remove unwanted undergrowth – cut back grass, trees, bushes, and creepers which may provide cover or access to the roof.
Dispose of fallen fruit, seed and waste from aviaries and chicken pens and pet faeces.
Do not use open compost heaps.
Do not compost any animal products (fish, meat, chicken, cheese, butter) or pet faeces.
Leave out just enough pet food for pets to eat soon after it is placed there.
Store poultry food in vermin proof containers with close-fitting lids.
Block access points to cupboards containing food and food-preparation utensils.
Cover rainwater tank openings and floor vents with wire mesh no coarser than 1mm and check and maintain these regularly.
If rodents are present:
secure all foodstuffs in sealed containers
throw away food or drink that may have come into contact with rodents
wash cookware and cutlery in warm water and detergent before use
wash hands thoroughly before preparing food, eating, drinking or smoking
wear shoes and do not lie or sleep on areas where rodents have been active. If you are bitten by a rat or mouse, consult your doctor promptly.
Chemical control should only be considered as part of a broader control program of eliminating food sources and rodent harbourage. Chemical control is generally short-term and rodents will return if food and shelter are still available.
Rat poisons or rodenticides containing an anti-coagulant can be purchased from hardware stores or supermarkets.
If you have questions regarding chemical control measures or are uncomfortable using chemical baits contact a licensed pest control operator.
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 offensiv odour.
Pets and children may eat toxic baits or poisoned rodent bodies.
Some individuals are sensitive to rodent control chemicals in their environment
Extreme care must be taken when storing and using poisons (read instructions carefully) to prevent the danger of children or pets being accidentally poisoned.
Mouse and rat traps differ in size and strength. It is important that the type of rodent is identified and the proper trap used. Traps can be purchased from hardware stores or supermarkets.
Some tips for setting traps:
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.
Disposal of dead rodents
Dead rodents should be carefully removed from areas where pets or native animals may access them.
Dead rodents can be buried or wrapped and placed into a domestic rubbish bin. Gloves should be worn when handling wild rodents.
Remember to wash your hands with warm water and soap immediately after handling any dead rodents.
Under public and environmental health legislation, it is the responsibility of owners and occupiers of premises to prevent rodents from living and breeding on their property.
Your local council can provide advice on pest control and may provide rodent baiting services or loan traps.
Councils can investigate rodent infestations following complaints, upon finding evidence of rodent infestation or conditions likely to attract them, may enforce a cleanup of possible food sources and nesting sites.
If you believe there is a rodent infestation at your home or nearby, contact:
an Environmental Health Officer at your local council or
Biosecurity SA for advice on rodent control for primary industry on (08) 8303 9620.
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