A snapshot of unloved aliens

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iol scitech aug 29 python

AP

12-foot Burmese python Houdini.

Paris - Following is a snapshot of some of the most notorious invasive species:

Rat (Rattus rattus). Originally a native of Indian sub-continent, the black rat, also called the ship rat or house rat, has spread almost everywhere, usually by hitching a ride on ships. Rats that crept aboard ocean-going canoes decimated island bird species as the Polynesians spread across the Pacific. Plants and other small mammals are also victims.

European wild rabbit (Oryctolagus cuniculus): Introduced by Europeans to Australia, New Zealand, South Africa and elsewhere as a food animal. Now a pest that causes billions of dollars in damages to crops and native plants.

Nile perch (Lates niloticus): Vorarious freshwater fish that can grow up to 200 kilos and two metres. Introduced to Lake Victoria in East Africa in 1954 for game fishing, the carnivore has contributed to the extinction of more than 200 endemic fish species. The Nile perch starred in a 2006 Oscar-nominated documentary, Darwin's Nightmare.

Cane toad (Bufo marinus): Central American toad introduced to Australia in the 1930s in the belief it would eradicate beetle pests, and instead became a pest in its own right. Weighing up to 1.3 kilos , the toad has poisonous skin that can kill predators such as snakes and freshwater crocodiles. Current total estimated at more than 200 million.

Water hyacinth (Eichhornia crassipes): Aquatic plant of tropical South America that flourishes in warm climates in Central America, North America, Africa, Asia, Australia and New Zealand. The hyacinth grows in thick rafts, deoxygenating the water for other species and impeding water flow and navigation. In Africa, the economic impact may be as much as $100 million annually.

Asian tiger mosquito (Aedes albopictus): Black-and-white striped carrier of West Nile virus, dengue, St. Louis encephalitis and a painful disease of the joints called chikungunya. Now a major worry in the United States, and a source of concern in Europe's Mediterranean rim. In both cases, the insect is believed to have landed in shipments of old car tyres, which retained pockets of moisture enabling it to survive the sea trip from Asia.

Zebra mussel (Dreissena polymorpha): Small stripey freshwater mollusc native to southern Russia and the Caspian which has spread to parts of North America, Britain, Ireland, Italy and Spain by hitchhiking a ride in the ballast water of ships. Mussel infestations are a major cost for power stations because they clog coolant pipes.

Burmese python (Python molurus): First found in Florida's Everglades swamp in 1979, where it may have been abandoned by a pet owner, the Burmese python took only 21 years to become an established species there. Lacking natural predators, the snake snacks on native birds, deer, bobcats and other large animals. Current estimate of its population run as high as hundreds of thousands. In August, University of Florida scientists examined a record 5.36-metre specimen that had 87 eggs.

Gorse (Ulex europaeus): Thorny shrub native to northern Europe that has been introduced to many countries by farmers seeking cheap enclosures for grazing animals. It becomes a pest by displacing native and cultivated plants and acidifying the soil. Gorse now grows in the Caribbean, Latin America, Australia, New Zealand, South Africa, the United States and elsewhere. - Sapa-AFP

SOURCES: The Invasive Species Specialist Group (http://www.issg.org/index.html); International Union for Conservation of Nature (http://www.iucn.org/); US Geological Survey (http://diseasemaps.usgs.gov/wnv_us_mosquito.html);

US National Invasive Species Information Centre (http://www.invasivespeciesinfo.gov/index.shtml);

New Zealand Department of Conservation (http://www.doc.govt.nz/conservation/threats-and-impacts/); news reports

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