9th May 2022
As the weather is cooling, a war is waged on the mice and rats that enter our homes and workplaces. But rodent poisons are doing more damage than you think. Here's how you can help.
You’re probably aware of the effectiveness of rodenticides (rodent poison) in keeping your home pest free- but are you aware that some of these poisons are absorbed by the predators who feed on rodents, causing disastrous effects in our ecosystems?
A 2021 study found Endangered Wedge Tailed Eagles are frequently exposed to gen 2 anticoagulant rodenticides. The researchers detected anti-coagulant rodenticides in 74% of the eagles they collected. Image: Wedge Tailed Eagle with chick, (c) Trevor Rix
Second Generation Anticoagulant Rodenticides (SGARs/Gen 2) poisons have increased in popularity in recent years due to their ability to kill rodents in just one dose- which is great for us, but not so great for the environment and our ecosystem. These hugely concentrated levels of poison easily work their way up the food chain when rodents are eaten by predators such as eagles, hawks, owls, devils, quolls- and even domestic pets. In a 2021 study, it was found that a whopping 74% of eagles examined had some level of rodenticide in their systems.
In a West Australian study on Southern Boobook owls; over 70% of studied birds had anti-coagulant compounds in their tissues, of which 18% had lethal concentrations (Lohr & Davis 2018). These results raise the concern that a similar trend may be occurring in Tasmania’s boobook owls. Image: Boobook owl (after sitting in the rain...), (c) Raptor Care North West
What can we do?
As the colder months approach, rodents are looking for shelter- and you may find yourself with a few unwelcome rodent guests in your home. So, if rodenticides are causing harm to our ecosystem, what other options do you have for pest control?
As always, prevention is better than cure. Avoid leaving food scraps/pet food in accessible areas, keep your yard free of fruit fallen from trees, and ensure your home is secure with no entry points for mice or rats (if your little finger can fit, so can a mouse!). Before you rush to buy poisons, you can also consider manual rat traps.
However, if you find yourself in a situation where poisons are necessary, opt for first generation poisons with the active ingredients warfarin or coumatetralyl. While first generation (Gen 1) poisons take multiple doses to kill rats, they have a lesser impact on the animals which prey on them.
If a poison contains dangerous chemicals such as bromadiolone, it is legally required to be labelled ‘POISON’. If its ingredients are less toxic, it will be labelled ‘CAUTION’. This distinction is very important, and will help you identify which products are best to use. While no poison is always the best option, if it is needed, opt for those with a ‘caution’ label.
Image: The warning label can be found at the top of the packaging.
- Opt for prevention and manual traps for the least environmental damage
- If necessary to buy poisons, look for those with active ingredients like warfarin and coumatetralyl, or those which contain sodium chloride.
- Always avoid poisons labelled ‘one dose action’ or ‘one kill’. These are second generation poisons which have long lasting effects in the ecosystem.
- The most toxic rodenticides will be labelled ‘POISON.’ Avoid these products. CAUTION is better than POISON
- ALWAYS avoid rodenticides with active ingredients that start with “bro” – Bro’s are a no go.
🔍For more information, visit
Landcare Tasmania CEO Peter Stronach talks rodenticide impact and how consumers can make informed choices on ABC Sundays.
Image (c) Raptor Refuge