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….

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