Tuesday, April 20, 2010

Cane toads, the slow invasion of Australia

Predator species have been introduced by humans in new environment since centuries. Sometimes purposely like in the case of rodent control, or sometimes accidentally. In either case, the introduction of another species is never good for the environment as it always has negative and serious consequences on native/endemic species and ecosystem balance. For example, humans have introduced Polynesian rats in the islands of Hawaii in order to control insect damage on local agriculture. Unfortunately the rat population grew far too much and when it began harming the environment, humans (them again!) introduced the Indian mongoose (Herpestes auropunctatus) to eat the rats. However, a new issue rose: Mongoose preferred feeding on bird eggs! As a consequence, the Hawaiian goose came close to extinction and rats kept on damaging sugar cane plantations.

This was in 1883, but we still haven't learned the lesson and find ourselves repeating the errors of the past. This is the story of the cane toads of Australia. Originally from Central and South America, the cane toads were introduced in Australia in the 1930's in order to control the invasion of beetles damaging here again sugar cane plantations. The population of cane toads grew exponentially and spread across most of Queensland and now reaching Darwin in the Northern Territory as well as the north of New South Wales. Not only damaging local ecosystems, cane toads have a toxic gland on their back that they use as defense when attacked. Local animals such as snakes and crocodiles feed on other amphibians and die when attacking cane toads.

From 62,000 toadlets introduced in 1937, the Australian population is now estimated to over 300 million toads. Sadly enough, the cane toads never solved the beetle issue as plantations did not offer the right shelter for these toads during the day...

Below is a very interesting 5-part documentary entitled "Cane Toads, an UnNatural History". Enjoy

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