ECU Honours student Bridget Duncan tested the resistance of mice populationsin metropolitan Perth to a common and particularly potent brand of rat poison.

Her study showed house mice are particularly vulnerable to rat poison inWestern Australia.

She and her supervisors were surprised to discover local mice lacked a genemutation found in mice around the world that helps to resist the effects ofrat poison.

“Mice in Europe, the United States and Canada have all been found to carrythis mutation and we assumed that mice in Western Australia would be thesame,” Ms Duncan said.

“However, results told a different story. This is particularly surprising asrat poisons are much more accessible to consumers in Australia compared toother parts of the world and we assumed they would have built up resistanceover time.”

This was the first investigation to test for this mutation in Australian miceand results may have implications for mouse control around the country.

Building resistance over time

Rat poisons such as warfarin has been used to control rodents for more than 80years, and as rats and mice developed resistance to these chemicals, a newgeneration of more potent chemicals were developed.

“Over time the population gains resistance through animals inheriting theprotective genetic mutation from the survivors over generations,” Ms Duncansaid.

“As a result, the extremely potent second-generation chemicals are now widelyused around the world, including Western Australia, where they have adevastating effect on the local wildlife.

“Small native mammals, birds and reptiles are all killed by these potentpoisons, but our research has indicated there might be no need to be so heavyhanded with these chemical controls in Western Australia.”

Ms Duncan said the research team had speculated why Western Australia micewere so different from populations in other parts of the world, but moreresearch needed to be done.

“Mice in the Perth metropolitan area are all very similar to each other andare most closely related to British population of mice,” she said.

“It is possible that Western Australian mice arrived on the early settlerships before this genetic mutation arose in the British population.”

Researchers also sampled mice on Browse Island in the remote Kimberley tocompare against the Perth metropolitan mice.

“We found the mouse population on Browse Island was more closely related tosouth-east Asian mice so probably originated from Indonesian fishing boats,”Ms Duncan said.
“They also lack resistance to common poisons so environmental managers canemploy a very measured approach to population control through this method.”

Next steps in the research will examine the resistance of rats in WesternAustralia to the same poisons.

The study “Mus musculus populations in Western Australia lack VKORC1 mutationsconferring resistance to first generation anticoagulant rodenticides:Implications for conservation and biosecurity” can be read in full in the PLOSONE journal.

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