Researchers exploring methods of controlling the poisonous invasive reptile, Bufo marinus in Australia, are trying out different approaches in a bid to halt its progress further south .
The researchers, at Sydney University’s Shine Laboratory have been working on different approaches to deter cane toads for some years.
Teaching Quolls Not to Eat Cane Toads
One approach, curiously enough, is to discourage predators from attacking cane toads. The predators in question are Northern Quolls (Dasyurus hallucatus), a small marsupial from Queensland and the Northern Territory, that like other quoll species, is considered an endangered species.
Quolls are carnivorous scavengers that will also attack live reptiles. In parts of Queensland where the cane toad are multiplying, quolls are under threat, as they are poisoned by eating small toads or scavenging off dead larger ones. The toads have poisonous glands in their back as a defence against predators.
Cane Toad Sausages for Quolls
In order to discourage the quolls from eating dead or live cane toads and becoming poisoned, Shine Laboratory researcher, Dr Stephanie O'Donnell is feeding them cane toad sausages.
The sausages are made of minced cane toad legs laced with a chemical designed to make the quolls feel sick. After their unpleasant experience with the sausages, quolls are likely to avoid eating poisonous cane toads in the wild.
Dr O’Donnell’s research suggests that a quarter of quolls that have tried the cane toad sausages will avoid eating a cane toad. Her work is likely to contribute the protection of this highly endangered marsupial.
"Quolls have largely disappeared from the areas where cane toads occur," the head of the Shine Laboratory, Professor Rick Shine, explained. "We know from Stephanie's work that if you don't train quolls to leave toads alone, they're very likely to eat the first toad they encounter and die as a result.
“Her research is invaluable to the ensuring the future of Australia's quolls.”
Setting Meat Ants onto Cane Toads
Research by the scientists from the Shine Laboratory in 2009 showed some young cane toads at Katherine River in the Northern Territory were being eaten alive by ferocious meat ants (Iridomyrmex species).
The young cane toads were in danger from the carnivorous ants because, being an imported species, they did not have protective behaviours to avoid the ants. In particular, young toads were in the open during the hot parts of the day when the ants were actively foraging.
Building on this research, Professor Shine and his team, Drs Georgia Ward-Fear and Greg Brown, have been encouraging the ants with dollops of cat food. They observed the numbers of ants increased by four times when the cat food baits were laid.
Meat Ants Kill More Cane Toads
In 2009, the researchers observed the meat ants attacking and killing young toads at the metamorph stage – the first stage of the toad's terrestrial development after emerging from the water.
After luring more ants to the area with cat food, the Shine team reported that ant densities and toad mortalities increased "more than fourfold". The result was not only many more cane toads killed, but toads that were bigger than young metamorphs.
Over 50 per cent of attacks were immediately fatal to the toads, while 88 per cent of 'escapee' toads died within 24 hours of being bitten.
"We can look at an interaction that's already happening, meat ants are already killing thousands of cane toads," Professor Shine explained. "We're just looking to make it a bit easier for them."
One Method of Controlling Toads
Meat ants as a weapon against cane toads was an intervention that could be used with low risk of collateral damage to native wildlife, Professor Shine said. What’s more, it was logistically feasible, low technology and inexpensive. While meat ants posed little enduring threat to native frog and toad species, cane toads were poorly-equipped to escape them.
"If we understand the vulnerability of the cane toad we can develop a number of combined tactics to combat this deadly invader,” Professor Shine said. "No single control will be a silver bullet to eradicate the cane toad from the Australian landscape.
“However, if we understand the biology of cane toads and their interactions with Australian fauna we'll be in a much better position to control them." The research into encouraging meat ants will be published in the February 2010 edition of the Journal of Applied Ecology.
For more on cane toad research, you might like to read Cane Toads Threatened by Predatory Meat Ants, Radical Ways to Control Cane Toads and Back Pain in Poisonous Cane Toads.
Sue Cartledge - I'm a science, health, nutrition and lifestyle journalist, fascinated by the way the physical world operates in all its forms, and how ...
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