Invasive predators can severely reduce the population sizes of native species, or even drive them extinct, because native prey species may not have evolved defenses against the novel predators.
- The predatory brown tree snake
The predatory brown tree snake was introduced to Guam in cargo from the Admiralty Islands. Predation by brown tree snakes eliminated ten of the eleven native bird species endemic to the forests of Guam.
2. The Nile perch
The Nile perch, a voracious predator, was introduced to Lake Victoria in Africa as a food fish. Predation from the Nile perch has eliminated over one hundred species of the spectacular native cichlid fishes of Lake Victoria.
3. Invasive herbivores
Invasive herbivores can cause great damage. For example, goats were introduced by sailors to many remote oceanic islands during the age of European seafaring exploration, to provide a source of food when the islands were revisited. But after Goats introduced to the island of St. Helena in the 16th century eliminated over half the endemic plant species.
4. North American gray squirrels
North American gray squirrels are driving native red squirrels to extinction in Great Britain and Italy. The introduced squirrels forage for nuts more efficiently than the native species, potentially leading to the loss of a native species.
5. Zebra mussels
Zebra mussels were accidentally brought to the United States from Russia in the ballast of ships, as a result Zebra mussels alter aquatic habitats by filtering large amounts of water, thus reducing densities of planktonic organisms and settling in dense masses over vast areas. This causes at least thirty freshwater mussel species are threatened with extinction by competition from the zebra mussel.