Scientists from the University of Sydney are getting creative with their efforts to combat destructive cane toad populations in Australia and to protect native species from the pests.
Cane toads, which were introduced to Australia in 1935 from Hawaii in an attempt to eradicate cane beetles, have caused a decline in other native species populations, such as snakes, lizards and quolls. Scientists have been trying to control the spread of cane toads for years; recent experiments have shown progress.
For example, Georgia Ward-Fear and colleagues used open cans of cat food to lure native meat ants to the shores of ponds inhabited by baby cane toads. Once there, the meat ants turned to the baby toads for a food source. Since the toads’ natural defense mechanism is to freeze and secrete a poison from glands in their backs, the effort is no match for the impervious meat ant. Rick Shine, who heads the lab where both studies were conducted, describes the interaction in a Reuters article:
All we’re doing is encouraging the ants to flourish somewhere where they already flourish, letting them know there’s particularly good food around so we get more of them down there on a very short-term basis. Baby toads are incredibly stupid and their reaction to being attacked is to freeze. I think they’re trying to advertise the fact they’re poisonous and let the predator get a taste of that, but it doesn’t work for the ant because it isn’t affected.
The results, published in February edition of the Journal of Applied Ecology, are impressive: the meat ants attacked 98% of the toads within the first few minutes. In addition, over 50% of the attacks were immediately fatal and 88% of escapee toads died within 24 hours.
In other research, Stephanie O’Donnell and colleagues are training quolls, one of the predators affected by the toads, to avoid eating the poisonous amphibians. Quolls, most of which are listed as threatened, are carnivorous marsupials related to the Tasmanian devil. They rely mostly on insects, birds, rodents and amphibians as a food source. However, since the cane toad is non-native, quolls are not predisposed to avoid them. Shine explains in a press release:
Quolls have largely disappeared from the areas where cane toads occur. 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.
The researchers are attempting to train the quolls to associate the taste of cane toads with becoming sick. They are introducing the quolls to sausages made from cane toad frog legs and which are laced with a nauseating chemical. Research suggests that a quarter of quolls will avoid eating a cane toad if they have sampled one of these laced sausages. Says Shine in another release:
No single control will be a silver bullet to eradicate the cane toad from the Australian landscape. 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.
Ward-Fear, G., Brown, G., & Shine, R. (2010). Using a native predator (the meat ant,Iridomyrmex reburrus) to reduce the abundance of an invasive species (the cane toad,Bufo marinus) in tropical Australia Journal of Applied Ecology DOI: 10.1111/j.1365-2664.2010.01773.x