Wednesday, 26 October 2016


Professor Rick Shine of Sydney University recently won the Prime Minister's Science Prize for research into helping northern Australia's peak predators to survive the cane toad invasion.

Cane toads were introduced to the north Queensland sugar cane area in the 1930s in the mistaken belief that they would eradicate the cane beetle.  Since then they have been steadily spreading south and west. To the west they have moved across the Queensland savanna into top end of the Northern Territory ( including into Kakadu National Park) and  further west  into the Kimberley region in the north of Western Australia.

Cane toads (Rhinella marina) are poisonous through their life cycle. As these introduced pests advanced, they brought devastation to native wildlife which sought to prey on them in the areas they have colonised.  Goannas, snakes, freshwater crocodiles, quolls and dingoes are some of the native species which have died as a result of the toad's poison.  It has been estimated that up to 95% of native predators have been killed as this introduced pest moves westward.

Professor Shine became an expert on cane toads while he was researching snakes on the Adelaide River floodplain south of Darwin in the Northern Territory. The frontline of the cane toad invasion consists of large, highly toxic adult males.  They are so toxic that a meal of one toad is sufficient to kill a Yellow-spotted Monitor, a goanna.

In his research Professor Shine has been dropping juvenile toads ahead of the invasion line.  When the native predators eat these they get sick but do not die as the juveniles are less toxic.  As a result they are less likely to prey on the larger toads when they arrive.

Initial studies have shown mortality rates dropping below 50% among goannas  after the toads arrive.

The professor has further developed his theories working with Dr Ben Phillips at the University of Melbourne. They have discovered a genetic variation in toads that governs how quickly they spread.

“Genes that make a toad go faster move to the front,” Professor Shine said.  “The genes that say ‘take a night off’ stay at the back.”

By dropping slower dispersal juveniles ahead of the fast moving frontline, the professor is not only training predators not to eat the larger, deadly toads but is creating a “genetic backburn” to slow down the advance.