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HomeNewsScientist warns pesticides harming native wildlife

Scientist warns pesticides harming native wildlife

A distinguished scientist is among numerous animal welfare specialists warning that native fauna on the Northern Beaches, including possums, bandicoots, lizards and birds, are being indiscriminately killed by second generation pesticides.

Furthermore, far from reducing invasive pests, toxic baits and sprays may actually be enabling them to proliferate.

Toxicology expert Edwina Laginestra is a wildlife carer with Sydney Wildlife Rescue. She is also renowned for her considerable knowledge on a range of wildlife-related subjects. These include her detailed research papers on toxicology and sustainable land use; a scientific assessment on the impact of the Harbour Tunnel Beaches Link on groundwater and the endangered bat colony at Burnt Creek, Balgowlah; and sensible animal welfare advice, such as what to do when you find a baby bird on the ground.

Edwina explained to Manly Observer how relying on pesticides, instead of modifying human behaviour, is what enables ‘pest’ species like introduced rats to proliferate.

“We provide perfect habitat for unwanted black and brown rats by removing native vegetation, having loads of food sources and providing lots of hiding spots in our junk. Yet we don’t provide food for natives to compete. We don’t really think about how a system works.

“The best way to manage rodents would be allow the raptors to do that – the kookaburras, the owls, even magpies. But we remove the trees they nest in, and of course we are now killing them too, by baiting the rats [they feed on].”

Barn owl dying from rat bait poisoning. Photo: Cameron Graham

Pesticides don’t decide what dies

Pesticides consist of herbicides, insecticides, fungicides and rodenticides. These poisoned baits, pellets and sprays are used to target ‘vermin’ (mice, rats, rabbits, foxes, etc.) and weeds. However, they filter into the natural environment and through the food chain to kill non-target species.

When sick animals come into your care, and you have diagnosed they’ve been poisoned, is it relatively easy to identify whether the toxicity is caused by pesticides?

“It’s not always easily determined,” Edwina revealed, “as some internal bleeding from major impact (e.g. a car) will also have white extremities and bleeding out from orifices. But usually with cars there are other signs of impact – pain, head injury, concussion.

“When you get in an animal with very white paws and nose and gums, then that’s very likely rat bait. They are also easy to handle, with their flight-and-fight response [resistance to capture] gone. They may also have swelling in face and gasping for breath. They can also have spotting (bleeding from capillaries)…”

Scientist Edwina Laginestra with one of the possums in her care. Photo: Alec Smart

She continued, “That’s the rodenticides… There are different types of rodenticides; the anticoagulant ones like warfarin (1st generation) and brodifacoum (2nd generation) both prevent blood clotting, so the victim bleeds to death. There are also non-coagulant rodenticides including strychnine and zinc phosphide, but they are not approved for general public use.

“For herbicides, the symptoms are very different. They usually have foaming at the mouth and often paroxysm [seizures]…”


Rodenticides are usually formulated as baits with attractive flavours – such as fish oil or peanut butter, or meats, grains and fruits, depending on the target creatures – to more effectively lure the species that eat them.

Rodenticides come in a number of different forms; some, such as the anticoagulants (that are popular with the public and favoured by councils), prevent the blood from clotting, causing a slow death through internal haemorrhaging.

Anticoagulant rodenticides are divided into two main groups: FGARs and SGARs.

According to the Federal Government-run Australian Pesticides and Veterinary Medicines Authority (APVMA): “First-generation anticoagulant rodenticides (FGARs) are referred to as ‘multi-dose anticoagulants’, meaning that rodents must consume these baits for several consecutive feedings to consume a lethal dose.

“FGARs break down in rodents quicker than second-generation anticoagulant rodenticides [SGARs], so there is less chance of secondary poisoning occurring in non-target animals if they eat rodents poisoned with an FGAR.

“There are 3 FGAR active constituents currently registered for use in Australia: warfarin, coumatetralyl and diphacinone…”

Echidnas are also vulnerable to poisoning from insecticides and herbicides. Photo: Alec Smart

Edwina summarised how FGARs work. “First generation rodenticides may take multiple doses to kill a rodent – so if only a nibble was taken once, it is possible the animal could recover, but they’d be slower and sicker and for any prey species that isn’t a good thing. Also if they do suffer impact, then they may well bleed out as the blood can’t clot quick enough.

“For the SGARs I doubt they’d survive without intervention.”

According to APVMA, SGARs are significantly more dangerous in the natural environment.

“Second-generation anticoagulant rodenticides (SGARs) are referred to as ‘single-dose anticoagulants’. A lethal dose can be ingested in a single feeding, making SGARs substantially more potent than FGARs. SGARs are slower to break down than FGARs and pose a higher risk of secondary poisoning to non-target animals.

“There are 5 SGAR active constituents currently registered for use in Australia: brodifacoum, bromadiolone, difethialone, difenacoum and flocoumafen…”

Possum rescue

Recently, Edwina took custody of a newly-born possum whose mother had died in unknown circumstances. Two days after coming into care spots appeared on his belly – a sure sign of rodenticide poisoning – which then identified what killed his mum.

“We had reports someone had been baiting possums intentionally when this one was found, his mum already dying…”

Red spots on this baby possum, whose mum died shortly after being found, indicate rodenticide poisoning. Photo: Edwina Laginestra

The young male was given massive doses of vitamin K, which enables the blood to clot and can reverse the effects of anticoagulants.

Edwina revealed, “We also had to treat him for pneumonia. He was 3 months in care as I also needed to give him physiotherapy and climbing room to get his muscle tone back before he was eventually released.”

She added, “A lot of rescues I do have been homeowners spraying for ticks, but poisoning their resident ringtail possum instead.”

Lobbying Council

At an Ordinary Council Meeting held on Tuesday 18 October 2022, Edwina addressed Northern Beaches councillors on the hazards of using SGARs to control vermin.

The following month, on 2 November, Council’s Parks and Recreation department sent her a written confirmation that “SGARs are used by Council to control rat infestations in a number of locations around the Northern Beaches,” adding that they will consider “how we may be able to phase out use of SGARs by staff, contractors and tenants on land owned by the Council.”

Can councils, including Northern Beaches, effectively reduce their spraying of herbicides to replace them with ‘environmentally friendly’ alternatives, without harming wildlife?

“A while back Integrated Pest Management (IPM) was a thing where you had to consider what you were spraying, and when,” Edwina replied. “But it takes brains and patience and actually looking at what you have. That isn’t popular for anything large-scale. They work on timetables, and if that includes removing all the new tips on food trees [that sustain wildlife] and cutting down branches in spring, that’s what we get.”

Young possums recovering in Edwina’s care. Photo: Edwina Laginestra

She continued, “I’m sure they do spray ‘environmentally friendly’ chemicals like pyrethrin, but at the same time they don’t provide alternative foods for native birds and animals, because they never actually think about it…”

Sydney Wildlife Rescuehttp://www.sydneywildlife.org.au

Manly Observer previous reporting on wildlife carers…






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