Scientists sound alarm as rat poison found in native snakes and lizards

Native lizards have been discovered with rat poison in their livers. Picture credit: JJ Harrison (

Native snakes and lizards harbour rat poison in their livers that act like toxic time bombs and spread poison through the ecosystem, scientists have discovered.

Before now, little was known about the impact of rat poisons on reptiles.  But researchers have sounded the alarm after they discovered reptiles transfer rodenticides to other animals by carrying it around with them.

Curtin University ecologist Damian Letoof says that reptiles use energy slowly, so end up shedding contaminants over a long time, even when the rat poison is consumed at low concentrations.

“The use of second-generation anticoagulant rodenticides is becoming a real concern around the world,” Mr Letoof says.

“We found a dugite with five different rat poisons in it.”

Anticoagulant rodenticide (AR) is a type of blood thinning poison that stays in blood tissue, by thinning the blood, rat poison prevents clotting and causes spontaneous bleeding.

It is well known that rat poison is causing problems in predators such as owls and eagles, with the birds eating dying mice who are slow-moving because of the poison.

Mr Letoof says there’s also a lot of evidence that shows insects, such as cockroaches and crickets, are consuming the bait too, passing the contamination onto insectivorous plants and birds.

Mr Letoof says there are a large variety of rat baits available and this means poisons can build upon one another causing their effects to be enhanced.

The research uncovered frequent exposure of the poison in the animals studied to be 91 per cent in dugites, 60 per cent in bobtails and 45 per cent in tiger snakes.

“Now they’re finding rodenticidal traces in frogs, other mammals, snakes and other reptiles that don’t even pray on rodents so it’s quite far reaching,” Murdoch University veterinarian  Dr Lian Yeap says.

Dr Yeap says rodenticides are also reaching ecosystems through contamination in water run-off, making it difficult for animals to avoid even when drinking.

There are options for baiting that involve using stations with small access holes only meant for rodents, however lizards such as the bobtail still have the ability to access these traps allowing them to eat the bait and become a vector for the rodenticides.

“One of the biggest issues is that rat bait is so readily available you can go down to the hardware store or the supermarket and buy it off the shelf, it’s completely unregulated,” Dr Yeap says.

She says education and building awareness around the collateral damage of using rat poison could be a good solution to help stunt the problem.

“The number one management method we could do is restrict the public use of rodenticides, that’s going to dramatically cut out urban wildlife being exposed,” Mr Letoof says.