ECOLOGISTS in Australia have discovered that cane toads are susceptible to being killed and eaten by meat ants – and much more susceptible to the ants than are native Australian frogs.
They claim that their research – published in the British Ecological Society’s journal Functional Ecology – reveals a “chink in the cane toad’s armour” that could help control the spread of this alien invasive species in tropical Australia.
Professor Rick Shine and his colleagues Georgia Ward-Fear, Matt Greenlees and Greg Brown from the University of Sydney’s Team Bufo (from the Latin name for the toxic toad) compared habitat use and activity patterns in meat ants, metamorph cane toads and seven native Australian frog species. They found that, unlike the native frogs, cane toads are poorly equipped to escape the meat ants.
According to Shine: “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.
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 a series of laboratory experiments, Team Bufo looked at when the ants, frogs and toads were most active, where they chose to live, and how good the frogs and toads were at escaping attacking meat ants. They found cane toads opt to live in open microhabitats and are active during the day, patterns that match those of meat ants. By contrast, native frogs are nocturnal and are safely ensconced in vegetation or other shelters during the day, when meat ants are on the hunt.
Cane toads are also less well equipped to escape attacking meat ants, Team Bufo found. Using a specially-built runway, they tested the frogs’ and toads’ sprint speed and endurance. They found that compared with the quick and nimble native frogs, cane toads’ hops are shorter and slower due to their shorter shin bones. Native frogs were also more vigilant for meat ants than cane toads, they discovered.
The results are interesting not only because they reveal the cane toad’s Achilles’ heel – a weakness that could be exploited to help control the spread of the toxic toad – but because the same “evolutionary trap” could be used to snare invasive species elsewhere.
“The end result of this mismatch between traits of metamorph cane toads, which evolved in the Americas, and the ecological interaction between metamorph toads and meat ants in tropical Australia, is an ‘evolutionary trap’. That is, characteristics that increased toad survival where they evolved in the Americas are now a disadvantage, because the toads are facing different challenges in Australia – challenges they have not evolved to deal with. Such evolutionary traps should be especially common for invasive species, because so many aspects of their environment differ from those in which the traits of that species evolved,” says Shine.
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Notes
Georgia Ward-Fear et al (2009). Maladaptive traits in invasive species: in Australia, cane toads are more vulnerable to predatory ants than are native frogs, Functional Ecology, doi: 10.1111/j.1365-2435.2009.01556.x
Photograph of the Meat ant, Iridomyrmex reburrus, from
www.antweb.org via http://www.canetoadsinoz.com/meatants.html
This post is based on a media release from the British Ecological Society.
Jennifer Marohasy BSc PhD is a critical thinker with expertise in the scientific method.
You sure this isn’t another 01/04
Now, that is cool science! It has the potential to solve a problem. Much unlike “climate science,” which seems to be devoted entirely to trying, desperately, to prove there IS a problem!
it has it’s own problems – obviously the ants are killing toads and have been for sometime, they just aren’t effective enough for us to have noticed.
If we were to increase the number of ants then the natural prey of the ants, other native species, will suffer along with the cane toads.
This is just headline grabbing science.
I like toads….. Go the toads! Plucky immigrant Queenslanders;-)
Actually the toads have caused no extinctions or real problems…. According to one expert all that has happened is that Australia is a proud owner of another animal species…. Our net biodiversity went up by 1.
here is a link to that. http://www.canetoadsinoz.com/evolutioncausedbycanetoads.html
I agree with jae. This is good science, because it increases our understanding of Nature. The fact that people are writing and talking about the meat ant study does not diminish its scientific value.
Are there practical applications down the road? Who knows? Basic research is every bit as valid as applied research. It’s not necessary to save the Universe in order to be a good scientist.
“It’s not necessary to save the Universe in order to be a good scientist.”
no but it is necessary if you want to get published in the MSM with it’s associated brownie points for your employer.
Since the environment didn’t change causing the toad population to decline, rather the toads are simply pushing the envelope on the range of habitats they are physiologically and behaviorally suited, how are the ants an example of an “environmental trap?” The invasive toads themselves represent a classic example of an “enivironmental trap” to the native predator population who mistake the toad as a source of food.
This may be the first case study of an environment trap falling victim to another environmental trap? I’m confused.
Furthermore, is a so-called “evolutionary trap” with low effectiveness really a trap or is it an evolutionary accelerator as it naturally weeds out the worst of the maladaptive traits the original population of cane toads arrived with, while allowing the more fit to pass through the filter–ie nocturnal behavior is selected for over diurnal?
Invasive species (like all species for that matter) are not finished works of nature but complex systems that rapidly evolve when exposed to ecological pressures. The way this article is composed give the impression that the cane toads are not evolving and adapting, in fact, they are.
I agree with Janama. This is typical of the way science is reported today. What is a perfectly warranted study is puffed up to sound like the cure for cancer had been discovered. If the context was more obscure we wouldn’t have a clue. But in the case of cane toads it seem probable the meat ants are only a minor limiting factor on toad populations as they expand their habitat range to the margins.
Following J Hansford link leads to another, much different and to my mind better, description of Team Bufo’s meat ant work.
This time without the good prof. Rick Shine jumping in to explain “honor student” Georgia Ward-Fear’s field work in the terms of an “environmental trap.” Hmmm.
“Georgia spent many hours out in the hot sun-exposed edges of waterbodies, watching how ants and toads interact. She found that ants are very effective at capturing and killing the small toads as they emerge from the water. Even baby toads that “escape” from the ants often die within the next few hours, because they have been fatally wounded by the ants. In some of her trials, ants attacked and killed more than 90% of the toads near the water’s edge within a short period of time. ”
http://www.canetoadsinoz.com/meatants.html
I am rather taken with the image of the ant’s head. Beautiful, including in its simplicity.
but if you watch them they are far from simple 😉
But how many ants does it take to eat a toad?
numbers ain’t a problem for ants. 🙂
Stoopid question from a Merkin. What about keelback snakes? My understanding is that they eat the smaller cane toads, without being affected by the toxin. Is the native keelback population slowly increasing? If yes, then there will eventually be an equilibrium, with fewer toads and more keelbacks to keep them in check. Or has that equilibrium already been reached?
“Actually the toads have caused no extinctions or real problems….”
J Hansford,
They’ve wiped out the Spotted Tail Quoll in our neck of the woods [it still survives in the colder country like the New England ranges where the toads don’t go]and decimated many other native species.
But in effect meat ants won’t slow ’em down much.
They’re so full of poison that it needs a smart predator to eat ’em without dying too and they reproduce by the thousands.
I don’t think meat ants are common enough.
If meat ants are so good at killing cane toads, why is there a cane toad problem?
Larry, good question. The keelbacks live in my area but I haven’t seen one in years and I generally see a fair range of snakes. Been eating too many bigger toads probably.
The big toads are so tempting because they are so slow.
What a great survival system. As your oldies develop more bile you feed them off to your enemies to eliminate them!
Our two worst ferals IMO are the dingo and the cane toad.
“But how many ants does it take to eat a toad?”
When I was a kid our favourite plough mare got bogged in a creek during a drought and when we found her a couple of days later she was being eaten alive by meat ants.
Not a pretty sight. [won’t go into details]. But you’ve probably read about pirates and the crab stakes.
A lady friend told me once that she used to get up early in the morning or late in the evening, get in her car and drive over cane toads on the road. She said “they make a satisfying pop when squashed under tier.” It was a huge problem in Aust