Eradication of predators and competitors

Case studies

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Unintentional deaths caused by human activities

-Dolphins killed as by-catch of tuna fishing or albatrosses caught on tuna long-lines

-Animals killed in fields during crop harvesting and as roadkill

Case study: The Nile perch

-Introduced to Lake Victoria in Africa in the 1950s to improve food supplies

-The Nile perch ate ingigenous fish species such as cichlids, some of which now extinct

-Overfishing reduced Nile perch numbers

-The Nile perch is much larger and the meat is preserved by smoking which requires wood to smoke. This put demand on fuelwood increasing deforestation and soil erosion

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Introduced species: Predators

- Water voles are killed by American mink that escaped from fur farms into UK rivers

- Many species in Australia threatened by the cane toads that were indroduced to control insect pests in sugar cane plantations. They're general predators.

- Small Asian mongoose introduced to Hawaii to control rats nesting in sugar cane fields. Devestated endemic (indigenous to a particular area and not normally found elsewhere) ground-nesting birds

-The ground-nesting birds on many oceanic islands like New Zealand, Hawaii ect. threatened by introduced cats, pigs, dogs

-Vegetation of many islands such as Round Island in the Indian Ocean seriously damaged by introduced herbivores such as rabbits and goats. Introducted deliberately by sailors hundreds of years ago so they would be "living larders" for future visits

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Introduced species: Competitors

-The Grey squirrel was introduced to the UK from North America in the 19th century. It out-competes the indigenous red squirrel as its better at using available food. It digests acorns better and being larger it can compete better for nest sites. Also carries squirrel pox killing red squirrels

-Rhododendrons introduced to the UK from Asia for their ornamental flowers and as cover for game birds. They're very invasive and shade the ground reducing growth of native vegetation

-The harlequin ladybird introduced to Europe from Asia, reaching Britain in 2004. Voracious predator and out-competes indigenous ladybirds. They also predate other ladybird species

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Introduced species: Disease

- Elm trees in Europe and North America killed by fungas accidentally introduced from Asia and been spread by bark beetles

- The signal crayfish introduced to the UK from North America to provide food. Carries a fungus disease that kills indigenous white-clawed crayfish

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