The cane toad ‘war’
Australia’s invasion by the cane toad (Bufo marinus) is a long-running epic battle. Scientists imported it from South America via Hawaii in 1935 to control insect pests in sugar cane fields (see box “Biological control—it’s not evolution”). Starting with 102 individuals, the toads have moved far from their initial east-coast beachhead. Moving north, south and west, they now occupy over a million square kilometres and are estimated to number over 200 million. A major factor in their success is a type of chemical warfare. The toad’s parotoid gland contains a powerful poison, bufotoxin, such that even if one of these invaders has been killed, it can cost the life of the animal that attacked it. This has devastated the local fauna.
Media outlets reporting on this war seem to be engaged, perhaps unwittingly, in another war—that of evolutionary propaganda.
The propaganda war
Media soundbites in this war have included how cane toads are “evolving longer legs to speed their invasion”;1 are “evolving” to be bigger, stronger, faster;2 and evolving “quickly”.3 We are told that we should control them as quickly as possible before they “evolve into a more dangerous adversary.”4 But another source tells us that they can’t be eradicated because they are “fantastic evolutionary machines”.5 An evolutionary “arms race” is reported in which snakes are also “evolving so that they can eat a cane toad and survive.”6 This is not confined to Australia; scientific publications in the USA7 and UK4,8 all use the cane toad invasion in Australia to show that evolution is happening today. But a closer look at the actual observations shows once again the confusion caused by the way the term “evolution” is used.
Are toads really evolving?
Cane toads exude and can squirt deadly poison, bufotoxin, from the parotoid glands on their shoulders when threatened or handled. Freshwater crocodiles, goannas, tiger snakes, quolls, dingoes and pet dogs have all died after eating cane toads.1 This photo shows a death adder, dead(!)—the cause of death all-too-evident.
- Cane toad: a case study, Biotechnology Online, biotechnologyonline.gov.au/enviro/canetoad.html, 21 October 2008.
With the toad invasion front rapidly nearing the city of Darwin, capital of Australia’s Northern Territory, researchers found that cane toads were advancing much faster than in the early years of colonization. Sixty years ago the toads were extending their range by about 10 km (6 miles) per year, but today it’s about five times faster.9,10
The frontline toads today are indeed “leggier”—toad arrivals in a new area have legs 45% of their entire body length, compared to 35% in older established populations.2 But is this “evolution” as most understand it, i.e., a process of unlimited change, with the capacity for adding lots of new information (and thus potentially turning a toad into something radically different in time)? No! As lead researcher Richard Shine comments (bold added), “any toad that happens to be born with legs that are a bit longer than normal and is a little bit quicker than normal as a result, is likely to be the one that gets to the invasion front. They have offspring—the fastest of those offspring will be the one at the invasion front the next year. And if you do that about … 70 years in a row, and toads, remember, have about 20,000 eggs in every clutch—there’s a lot of variation out there—you rapidly end up with this sort of race of super toads that are sprinting along like trained athletes.”2
Adapted from a stock.xchng photo
Since being released near Cairns, Queensland, cane toads have extended their range by up to 50 km every year, spreading into the Northern Territory and New South Wales. They are expected to one day reach not just into Western Australia, but also parts of South Australia and Victoria. [After Shine, R. (2007)5]
It’s clear that all that is happening is a simple genetic shift in the proportion of a population having a particular characteristic that already exists in that population—in this case, long legs. The genetic information for long-leggedness has not appeared out of nowhere (i.e. evolved) but is part of the variation built into the toad kind at Creation.
This means of course that there are practical limits to that variation. Shine implicitly recognized this when he said: “[S]hort of evolving jet propulsion, it’s very hard for me to imagine the toads going all that much faster than they are now.”2
In fact, follow-up research has found that long-leggedness comes at a cost.11 The leggy toads at the frontline have a “remarkably high” incidence of severe spinal arthritis, with bony growths fusing some of their vertebrae.12-14 (Shorter-legged toads were not afflicted.)
Whatever the reason for this (e.g., loss of genes conferring resilience or mutational changes, i.e. gene copying mistakes), it is not atoms-to-amphibians-to-archaeologists evolution. But it is consistent with the biblical account that God created the various kinds of creatures to reproduce each according to its kind.
Such simple shifting of relative gene frequencies can go either way. A year after the invasion front arrived at their research site near Darwin, Shine and colleagues found that the average leg length fell back to 40% of body length, as the shorter-legged toads caught up.8
Do toads goad snake evolution?
As with the toads, Professor Shine’s claim that he and his co-researchers have observed “genuine evolutionary changes” in snakes6 does not stand up in the light of their actual observations.7 One sees that snake populations have changed to become “much less vulnerable” to the toxin in the toad’s skin. And these changes are again a simply understood shift in gene frequencies. Shine said:
“We’ve done a bunch of trials to see if it could just be that the snakes are learning and so forth but they seem to be remarkably stupid … Basically you’ve got a strong genetic component to feeding responses, and some snakes really go mad on eating frogs and others really want to eat nothing but mammals and so forth … even within a single litter of baby snakes you’ve got genetic variation in what kinds of things they treat as prey. And it’s just that the only snakes that survive after the toads arrive are the ones that happen to be born with a set of genes saying: ‘If it looks and smells like a cane toad, don’t eat it.’”6
Genetically-determined attributes such as the snake’s head and body size are key factors too. A snake with a small head cannot eat larger toads which have more poison; thus it has a better chance of surviving. A large-bodied snake has an advantage too, because it can withstand larger doses of poison. Shine says, “ … the right shape to be when the toads arrive is to be a big snake with a small head and that’s exactly the evolutionary change that we’re seeing in a couple of species of snakes”.6
Cane toads eat mainly insects, but will also eat any creature that fits into their mouth, including this extraordinary instance of a cane toad attempting to eat a Keelback snake.
But this is hardly evolutionary change. To get from pond scum to snakes requires an increase in genetic information, but these observations all involve a culling of information. Genes coding for large heads, small bodies and an urge to swallow a cane toad are being removed from snake populations by natural selection, no doubt reducing the existing “genetic variation”.15 This also decreases the potential for further change, of course, the opposite of what evolution would require. All this is another example of natural selection acting to favour certain already-existing genetically determined traits in the snake populations. Creationists do not dispute natural selection16—indeed, it is an integral part of the biblical Creation-Fall-Corruption-Flood-Dispersal worldview, and was theorized by creationists before Darwin.17
And you’d expect it to happen quickly—i.e., in just one generation you’d expect to see, in a population of snakes, an increase in the numbers of snakes with large bodies, small heads, and a decided lack of interest in hunting cane toads. But evolutionists, used to thinking that slow-and-gradual evolution over millions of years is how we got here, and that change through natural selection is evolutionary, are often caught by surprise at the rapidity of such changes.18 As Professor Shine admitted, “you would have expected that evolutionary change would be fairly slow”, but in relation to cane toads, “I’m amazed at the speed that it’s all happening.”6
Biological control—it’s not evolution
The cane toad was introduced to Australia in the hope that it would control two species of beetle (French’s cane beetle and the greyback cane beetle) which were decimating sugar cane crops. (The beetles’ larvae were eating the roots and stunting, if not killing, the plants.) As it turned out, the plan was unsuccessful. Adult beetles for the most part lived in the upper stalks of cane plants beyond the jumping reach of the toads—so toads did not eat them!1
No doubt farmers’ hopes had been raised by the success of an earlier biological control project. The Cactoblastis insect was deliberately released in 1926 to control prickly pear infestations, achieving spectacular success within just a few years. Such control has nothing to do with evolution. Farmers have used similar commonsense biological controls for centuries, well before Darwin. John Mann, the scientist responsible for the Cactoblastis introduction, was heaped with accolades and honours for his achievement, and was a convinced biblical creationist.2
The cane toad’s rapid spread is not a unique phenomenon. Rabbits were unknown in Australia before European settlers brought them, yet soon colonized a massive area, extending from their release sites in south-east Australia all the way to the coast of Western Australia. That these creatures could so quickly occupy vast lands simply by gradual spread, expanding their territory as they increased population numbers, puts paid to the idea that post-Flood migration would have needed tens of thousands of years. After the Genesis Flood, there was little resistance to animal invasion all around the world, with successive population waves of animals being able to readily occupy “empty” ecological niches in all directions.3
- Killing off the cane toad, The University of Queensland—Institute for Molecular Bioscience, www.imb.uq.edu.au/index.html?page=48437, 2003.
- Famous creation scientists—interview with John Mann, M.B.E., Creation 5(2):13–17, 1982; creation.com/mann.
- See Wieland, C., The grey blanket—What the story of Australia’s amazing rabbit plague teaches us about the Genesis Flood, Creation 25(4):45–47, 2003; creation.com/blanket.
The claims that the cane toad invasion in Australia demonstrates evolution crumble away in the light of the observed facts, which make perfect sense in the light of Scripture.
References and notes
- Dennis, C., Cane toads leg it across Australia—Pests are evolving longer legs to speed their invastion, Nature.com news, nature.com/news/2006/060213/full/060213-4.html, 15 February 2006. Return to text.
- ABC Radio National’s AM program, broadcast 16 February 2006, “Research shows cane toads getting bigger, stronger, faster”, transcript at abc.net.au/am/content/2006/s1571332.htm. Return to text.
- Lane, S., Evolved toads invading Aust at high speed, ABC News Online, abc.net.au/news/stories/2007/03/28/1883297.htm, 28 March 2007. Return to text.
- Phillips, B., Brown, G., Webb, J. and Shine, R., Invasion and the evolution of speed in toads, Nature 439(7078):803, 2006. Return to text.
- Shine, R., Toad kill, Australasian Science 28(6):16–20, July 2007. Return to text.
- Snakes vs toads—Fran Kelly interviews Professor Richard Shine, ABC Radio National “Breakfast” program, broadcast 6 April 2006. (An audio was available online for one month afterwards—a short written summarizing introduction remains at abc.net.au/rn/talks/brkfast/stories/s1609791.htm.) Return to text.
- Phillips, B. and Shine, R., Adapting to an invasive species: Toxic cane toads induce morphological change in Australian snakes, Proceedings of the National Academy of Sciences USA 101(49):17150–17155, 7 December 2004. Return to text.
- Leggier cane toads step up efforts to conquer Australia, New Scientist 189(2539):21, 2006. Return to text.
- The researchers radio-tracked toads moving at up to 1.8 km per day (i.e. at night) during the rainy months. Return to text.
- Phillips, B., Brown, G., Greenlees, M., Webb, J. and Shine, R., Rapid expansion of the cane toad (Bufo marinus) invasion front in tropical Australia, Austral Ecology 32:169–176, 2007. Return to text.
- Long-legged toads have Achilles’ heel, New Scientist 196(2626):23, 2007. Return to text.
- Brown, G., Shilton, C., Phillips, B. and Shine, R., Invasion, stress, and spinal arthritis in cane toads, Proceedings of the National Academy of Sciences USA 104(45): 17698–17700, 2007. Return to text.
- Spinal disease may hold back toad invasion, ABC News, abc.net.au/news/stories/2007/10/15/2059576.htm, 15 October 2007. Return to text.
- This parallels a very well-known characteristic of breeding programs—that selection for a particular trait is often associated with the loss of another. E.g., selection for firm-fruited strawberry varieties came at the expense of flavour. Batten, D., What! … no potatoes? Creation 21(1):12–14, 1998; creation.com/potatoes. Return to text.
- See Wieland, C., The evolution train’s a-comin’ (Sorry, a-goin’—in the wrong direction), Creation 24(2):16–19, 2002; creation.com/train. Return to text.
- Wieland, C., Muddy waters—Clarifying the confusion about natural selection, Creation 23(3):26–29, 2001; creation.com/muddy. Return to text.
- Grigg, R., Darwin’s illegitimate brainchild, Creation 26(2):39–41, 2004; creation.com/brainchild. Return to text.
- Catchpoole, D. and Wieland, C., Speedy species surprise, Creation 23(2):13–15, 2001; creation.com/speedy. Return to text.