Aus faces cane toad catastrophe
2006-02-15 08:17
Paris - He's fat, ugly and poisonous - and he's mutating.
He's the cane toad (Bufo marinus), a species which was introduced into the Australian state of Queensland 70 years ago to tackle insect pests in canefields and has since become an ecological catastrophe.
Weighing in at to up 2kg, the unwanted anuran has extended its range to more than a million square kilometres in tropical and sub-tropical Australia, crushing native species in its relentless advance.
A team of toad watchers positioned themselves on the front line of the invasion, 60km east of the city of Darwin, and for 10 months caught toads, some of which they radiotagged and let loose again.
They were astonished to find that the creatures can hop up to 1.8 kms a night during wet weather, a record for any frog or toad.
An example of evolution
But even more remarkable was the discovery that the first toads to arrive at the front invariably had longer hind legs than those which arrived later.
By comparison, the toads which are living in the long-established Queensland colonies have much shorter legs.
The case is being seen as a classic example of Darwinian evolution - animals that are stronger, faster or smarter are able to stake out new territory and defend it against those that are weaker, slower or less astute.
The findings also neatly explain a puzzle surrounding the cane toad.
From the 1940s to 1960s, the critter expanded its range by only 10 kms a year. Today, though, it is advancing at the rate of more than 50kms annually.
The reason: with longer legs, the mutating species is able to travel further, faster.
The authors, led by Richard Shine of the university's School of Biological Sciences, say the cane toad is a chilling lesson for governments to combat invasive species as soon as possible, "before the invader has had time to evolve into a more dangerous adversary".
- AFP