Rats and Mice
Rattus rattus; Rattus norvegicus; Mus musculus
Introduced rodents that gnaw ripe fruit, tubers and seed stores. Also a food safety risk.
Background
Three introduced rodent species are common garden and shed pests in Australia: black rat, brown rat and house mouse. They are omnivorous and will chew ripening fruit (particularly tomatoes and strawberries), tubers (sweet potatoes, stored potatoes), stored seed and compost scraps. Rodents also carry disease, and droppings on fresh produce are a food-safety concern.
How to identify
- Gnaw marks on fruit, especially at stem end
- Small parallel tooth marks
- Droppings — rat 10-20mm, mouse 3-7mm, dark pellets
- Tunnels in mulch and under compost bins; greasy rub marks along edges of sheds and walls
Life cycle
Fast reproduction: rats mature at 2-3 months and litter every 3-4 weeks. Populations can double in months in favourable conditions.
Weather triggers
- Temperature: -5-40°C
- Year-round pressure. Autumn and winter see indoor incursions; spring/summer see garden raids.
Peak season (southern hemisphere)
Red = active season · Dark red outlined = this month
Affected vegetables & crops
Click any crop to see current prices and growing info.
Climate zones at risk
Organic & low-impact control
- Snap traps are still the gold standard — humane, targeted, no bait left in the environment
- Remove food sources: harvest ripe fruit promptly, tidy fallen fruit, secure chook feed in metal bins
- Enclosed compost bins (tumbling composters, lidded bokashi)
- Encourage barn owls and brown goshawks by maintaining habitat (they take rats)
Chemical control
- Second-generation anticoagulant rodenticides are extremely damaging to native raptors and owls through secondary poisoning — avoid in home gardens
- If baits are essential, use single-dose first-generation anticoagulants in lockable bait stations only
Always read product labels — registrations change.
Prevention
- Seal gaps and holes in shed walls and roof cavities
- Do not leave pet food or compost uncovered
- Harvest ripe produce promptly
- Clear woodpiles and long grass near the house and garden
Companion planting
No reliable companion effect. Rodents are opportunistic — removal of food and shelter is the effective lever.
Biosecurity
Introduced species. Rodenticide residues in owls are a recognised conservation issue in Australia.
Sources
- Queensland Health — Pest rodents
- NSW DPI — Rodents in horticulture
- Birdlife Australia — Rodenticide and raptors
Accuracy confidence: high. We update this library as new extension guidance is published.