Have Australian cane toads finally met their match?

Jeremy Hance
March 31, 2009

This weekend in Queensland, Australia the government held the first 'Toad Day Out' where hundreds of locals went hunting for the invasive cane toad, catching an estimated 10,000 toads to be euthanized. At the same time, researchers announced in the journal Functional Ecology that they may have discovered a native Australian species that will finally rout the cane toad—and it's not man. The meat ant is a notoriously aggressive and abundant insect which is known to consume anything edible, including the scientists argue, cane toads.

Comparing habitat use and activity patterns of meat ants, cane toads, and seven native Australian frog species, the researchers found that the cane toad was by far the most susceptible to predation by meat ants.

Cane toad where it belongs: in the Amazonian rainforest of Peru. Photo credit: Rhett A. Butler.
"The spread of cane toads through tropical Australia has created major ecological problems. The ideal way to control toad numbers would be to find a predator that kills and eats toads but leaves native frogs alone. However, bringing in a predator from overseas might have catastrophic consequences, like those that occurred when cane toads themselves were brought in. So we've explored an alternative approach – to see if we could use a native predator," explains Dr. Rick Shine, one of the study's authors. “Meat ants are abundant around tropical waterbodies, and we often see them eating small toads, so we suspected that there might be some kind of mismatch between the invader and its newly invaded range, for example something about the toads' behaviour that makes them vulnerable to a predator that poses little danger to native frogs."

Through laboratory experiments Shine's team, known as Team Bufo (after the Latin name of the cane toad), found that both cane toads and meat ants live largely in open microhabitats and are diurnal, or active during the day. Native frogs, however, are active at night and spend their days hidden in vegetation, away from the path of the voracious meat ants. In addition, cane toads are slower than native frogs and appear to be less vigilant against meat ants: while native frogs would flee the ants, cane toads would only move a few short hops away or even bound closer. Perhaps, even more important, the meat ants were not affected by the cane toad's poison.

The next step according to researchers is to work to bring these two species together more frequently and see if results in the lab can be recreated in the field.

The story of the cane toad in Australia is a warning to anyone who thinks it wise to import species to non-native habits. A warning that has yet to be fully heeded: consider the recent difficulties in Florida with non-native burmese pythons.

Cane toads were introduced into Eastern Australia in 1935 from Hawaii, where they had been introduced from their native habitats in Central and South America. They were brought to Australia because it was believed they would help control the native cane beetle, a pest for sugarcane farmers. However, it turned out that the cane toads were not able to jump high enough to eat the cane beetles.

Instead of saving farmers, the cane toad began to devastate native wildlife. As large and slow-moving the cane toad proved an easy target for Australian predators, only the cane toad is poisonous and therefore would often kill anything that ate it, greatly affecting populations of quolls, birds, snakes, monitor lizards, and crocodiles.

Researchers have tried for decades to come up with a solution to Eastern Australia's cane toad plague, so far there has been no silver bullet.

Related articles

Cane toads are killing crocodiles in Australia
(07/30/2008) The cane toad has been a scourge to Australian wildlife for decades. An invasive species, the cane toad competes with local endemic frog species and due to its high toxicity kills any predator who preys on it, including snakes, raptors, lizards, and the carnivorous marsupial, northern quoll. New research has uncovered another victim of the toad. The freshwater crocodile has suffered massive population declines due to consuming the irascible toad.

Invasive Species: Toad-ally out of control
(05/18/2008) Throughout warm, wet climates around the world lurks a camouflaged combatant seldom known beyond those who experience first hand its awesome destructive powers. It is an ingeniously crafted destroyer equipped with a host of specially developed chemical toxins, a lightening fast attack, and the ability to easily navigate across both water and land. This devious tool is not a creation of human engineering or military research and development but a product of a much more ancient and refined process: evolution. And until human intervention it was neither ecologically harmful nor an invasive pest but a well-integrated part of ecosystems throughout South and Central America. Meet Bufo marinus — the cane toad: exemplary proof of how human short-sightedness and misuse of biological control agents often leads to the catastrophic mismanagement of our natural world in the form of a large, squat, hungry toad.

Cane toads to invade 2 million square kilometers of Australia
(04/03/2007) Cane toads are dramatically expanding their range in Australia and may eventually double their current extent to occupy over 2 million square kilometers, according to new projections by a team of scientists writing in Proceedings of The Royal Society B: Biological Sciences. The researchers report that the invasive amphibians increasingly occupying zones outside their native conditions, putting native Australian species at ever greater risk.

Photos of monster cane toad captured in Australia
(03/27/2007) A conservation group captured a giant cane toad in the Australian city of Darwin. The beast weighed 840 grams (1.8 pounds) and measured 20.5 cm (8 inches).

Invasive species is pestering Europe's rich
(03/24/2007) An invasive species is causing mounting concern among rich Europeans according to an article in today's edition of The Wall Street Journal.

Invasive predators more harmful to biodiversity than native predators
(03/20/2007) Alien predators are more harmful to prey populations than native predators finds a study published in the current issue of the journal Proceedings of the Royal Society B: Biological Sciences.

Cane toads increasingly a problem in Australia
(04/17/2005) Cane toads increasingly a problem in Australia

Jeremy Hance
mongabay.com (March 31, 2009).

Have Australian cane toads finally met their match?.