23 October 2016

Is there a food that once made you so sick the mere sight of it now makes your stomach turn? While food poisoning is an unpleasant experience, it could be the ticket to long term survival for one culturally significant lizard.

The yellow-spotted monitor or floodplain goanna is an important source of bush tucker for Indigenous people in the Kimberley and maintaining their populations keeps cultural practices and stories strong. However one invader, the cane toad, is having a significant impact on predators’ populations. Goannas are especially susceptible to the impacts of cane toads because they are top-level predators and can locate and consume the poisonous toads even when the toads are in low densities.

Fortunately, NERP researchers discovered a successful way of training goannas not to eat the poisonous pests, following a study in a remote Kimberley floodplain which began in 2013.

“We encouraged a group of goannas to eat young cane toads to provoke a kind of food poisoning response,” said lead researcher Georgia Ward-Fear from Sydney University.

“Juvenile toads are less toxic than adults, so it was enough to make the goannas sick, but not kill them.”

Around 65 goannas had high frequency transmitters fitted to their tails and the Balanggarra rangers used radio receivers and aerials to track the goannas while foraging. Once located, the goannas were offered a small cane toad dangling by a fine cord from a fishing rod. Their response to either eat or reject the cane toad was then recorded. The rangers continued to track the goannas over 18 months as cane toads began to invade the floodplain.

“At the end of the study, half of the trained goannas had avoided eating the toads. In contrast, almost all of the untrained goannas died within four months of the toads arriving,” said Dr Ward-Fear.

How can we use the research?

Researcher Georgia Ward-Fear holds a yellow-spotted monitor, photo Georgia Ward-Fear

Dr Ward-Fear says the research shows taste aversion training can prevent goannas from eating larger toads that could kill them.

“This study demonstrates that in-situ aversion training (releasing small toads in advance of the main invasion front) offers a logistically simple way to buffer the impact of invasive toads on large monitor lizards in the tropics,” said Dr Ward-Fear.

“We don’t expect a 100% increase in survival of breeding adults, but a 50% or even 20% increase in survival could be enough to buffer the impacts and allow the populations to recover far more rapidly than current trends. We also know that many other native species have the capacity to learn in the same way if given the opportunity.”

The project team is currently in talks with government, NRM groups and Indigenous landholders about how best to apply the research. It’s hoped the research will direct future conservation strategies ahead of the cane toad invasion.

“Losing larger predators such as goannas from the landscape destabilises ecosystems, especially in tropical Australia where these systems are extremely fragile. That’s why it’s so important to preserve this species where we can,” said Dr Ward-Fear.

Excitingly, Professor Rick Shine who led this research as part of a larger NERP project, was recently awarded the Prime Minister’s Prize for Science for his achievements in this field.

You can read more about the research here.

Top Image: Yellow-spotted monitor, photo: Georgia Ward-Fear