Researchers propose waterless barrier to stop cane toads in their tracks

[June 2014] 

Researchers were in Broome last month to share their ideas on how to control the spread of the ‘invincible’ Cane Toad past the Kimberley.

Research Fellow at the ARC Centre of Excellence for Environmental Decisions at The University of Melbourne, Dr Reid Tingley said the Cane toads have reached the Kimberley and there is no sign that their conquest is nearing completion. 

“The toads seem invincible, but we are interested in determining if there any chinks in their armour that might help us control their spread,” Dr Tingley said.

It turns out the answer might be in the toads’ inability to retain water. Few, if any toads can survive more than 10 days without water in the dry season. 

 “In very dry regions, we may be able to halt their spread by excluding them from permanent water sources. If we manage lots of water sources in the same area (e.g., by minimising leaks in tank and trough systems), we might be able to create a waterless barrier or ‘firebreak’ in the landscape that toads can’t penetrate,” Dr Tingley said.

The question is then posed – where could we manage all permanent water bodies to create a waterless firebreak? 

“It just so happens that toads will need to march south towards the Pilbara through an arid corridor where permanent natural water is in short supply,” Dr Tingley said. 

Artificial water points and natural springs dot the corridor, forming a thin strip of suitable toad habitat along the coast. The combination of landscape and climate makes this corridor a potential bottleneck (or choke point) in which to create a barrier.     

Researchers have forecasted the way toads might spread through this corridor by combining information on the biology of toads and the locations of water points, and preliminary analyses suggest that a barrier in the right location would stop the invasion dead in its tracks. 

“It looks like a waterless barrier might be a strategy that’s worth discussing, but what’s really needed is the input of pastoralists and people who know the country firsthand,” Dr Tingley said.

To work out the feasibility, practicalities and costs associated with this strategy, researchers from The University of Melbourne visited pastoralists between Pardoo and Roebuck over five days, and had a one-day workshop in Broome on 15 May. In total, almost 30 people were in attendance from a wide range of organisations, including Rangelands NRM, Environs Kimberley, Nyamb Buru Yawuru, Kimberley Land Council, Stop the Toad Foundation, the Federal Department of the Environment, and several state government agencies and universities.

Dr Tingley said overall, the road trip and workshop were a great success. 

“Perhaps the most promising aspect of the discussions was the realisation that a waterless barrier might create numerous opportunities for ‘win-win’ situations among environmentalists, pastoralists and indigenous communities,” he said. 

“For example, this idea could present an opportunity to improve infrastructure and water usage on pastoral stations, while implementing and monitoring a barrier could provide potential employment opportunities for indigenous ranger groups in the area.”

Dr Tingley said now that the workshop is over, there is plenty of work to do. 

“Over the next six months, we will refine maps of water bodies in the area, estimate how much a project like this might cost, and find the most cost-effective location for a barrier,” he said.

So watch this space! There’s plenty of exciting work to come.

Images
[Top left] Cane toads can reach remarkable densities around dams, like this one at Auvergne Station, NT (Photo courtesy of Ruchira Somaweera)
[Bottom right] Natural and artificial water bodies in the study area. The black arrow in the lower left-hand corner of the main figure shows the location of the De Grey River.