Controlling rodents and helping wildlife

There isn’t much worse than rats or mice getting into the pantry, scurrying through the roof or raiding the garden.

Rat bait is the solution many of us reach for, and while we ensure baits are put out of reach of children and pets, we rarely think about where rodents go after they have eaten baits.

In fact, we probably try and think about it as little as possible! Unfortunately, some of these products can be a huge problem in and of themselves.

The most commonly used rodent poisons are anticoagulant rodenticides (ARs). These act as blood thinners, so rats and mice can consume a lethal dose but not feel sick until later when the poison takes effect. In fact, it can take as long as ten days for a rodent to die after consuming ARs.

The worst of a bad bunch

The vast majority of the rat baits on our shelves are second generation anticoagulant rodenticides (SGARs). These are strong poisons and are powerful enough that a single feed is lethal, but because of the time lag between taking a bait and feeling the effects, poisoned rodents can wander around like walking time bombs. Predators like owls and kestrels, even magpies, can then easily consume multiple poisoned rodents, in turn becoming poisoned themselves.

The key differences between earlier, first generation anticoagulant rodenticides (FGARs) and SGARs is how long the toxins remain in the body. FGARs break down quickly, so secondary poisoning is very uncommon. SGARs can stay in body tissues for months or even years, yet Australia has little regulation on their use and can be easily purchased in hardware and grocery stores across the country.

Which animals are at risk?

We are only just starting to discover how disastrous these poisons can be in Australia. Almost 73% of samples tested in 2016 from southern boobooks in southwest WA had detectable exposure to ARs. Of even greater concern, about 18% of all the boobooks tested had levels of exposure that were high enough to kill them directly. Almost all the poisons were identified as SGARs. These were found in both urban and rural birds.

Since then the list of species known to be poisoned by these SGARs has grown and includes native birds like pigeons, parrots, ducks, ravens, and gulls; native marsupials such as possums and native rodents; reptiles like skinks and snakes; SGARs have even been detected in slugs. It isn’t only our common backyard creatures, but Tasmanian wedge-tailed eagles (a federal listed threatened species) and powerful owls (a state-listed threatened species) have both shown lethal and sublethal effects of SGAR poisoning.

What can we do as gardeners?

The Australian Pesticides and Veterinary Medicines Authority, is currently undergoing a review of anticoagulant rodenticides that will conclude in 2025. In the meantime, we as individuals can take action. Of course, the best thing to do is to stop using SGARs. Packaging for SGARs can be unclear, but as a safe bet avoid products with the ingredients brodifacoum, bromadiolone, difethialone, difenacoum or flocoumafen. We do need to control rodent problems though, so you should:

Make your house and garden less friendly for rodents

• Seal potential roof/wall cavity access points
• Pick up any fallen fruit
• Ensure excess pet food isn’t accessible
• Rodent-proof chook pens and aviaries using rodent excluding feeders and fencing
• Replace rat-friendly palms with owl-friendly trees
• Tidy up garden waste and limit access to compost heaps and brush piles
• Keep your compost heap moist and turn it over often, so that it breaks down faster – big chunks on the top are attractive to rats!

Encourage native predators

• Plant habitat trees
• Use logs, rocks and ponds in your garden to encourage frogs, lizards and other prey.

Reduce dependence on poison baits

Consider other non-poison pest control, like snap traps as a first course of action. The most effective spots to place snap traps are amongst high-activity areas like dark corners, along walls, behind appliances and objects, and all areas where droppings are evident.

• Read the labels on any poisons you buy and make the change to first generation anticoagulant rodenticides (FGARs) or other alternatives. Look for active ingredients like warfarin and coumatetralyl or natural constituents like sodium chloride
• Only put out baits when you actually need to and use a professional pest controller
• Use lockable bait stations and dispose of any dead rodents immediately.

Dealing with rodent control is never pleasant but we need to take action to protect our amazing wildlife. SGARs are already heavily regulated or banned in Europe and North America, and some proactive Australian councils are already phasing them out.

Find out more and join BirdLife Australia’s rodenticide campaign at actforbirds.org/ratpoison

Good baits available

• Ratsak Naturals (a human and pet safe bait option)
• JT Eaton Apple Bait Block Rodenticide
• Bayer Racumin Rat and Mouse Paste
• Ruth Consolidated Industries (RCI) Ratblitz Bait
• Parafarm Ratex Mouse and Rat Bait
• Yates RATSAK Double Strength Bait Station
• PCT Holdings Surefire Couma All Weather Blocks Rodenticide
• Motomco Tomcat All-Weather Rodent Block
• Tamper proof bait stations are available at all major suppliers