Recently Extinct Animals - Invasive Alien Species

Humans have been transporting animals and plants from one part of the world to another for thousands of years, sometimes deliberately (e.g., livestock released by sailors onto islands as a source of food) and sometimes accidentally (e.g., rats escaping from boats). In most cases, such introductions are unsuccessful, but when they do become established as an invasive alien species, the consequences can be catastrophic. Invasive alien species can affect native species directly by eating them, competing with them, and introducing pathogens or parasites that sicken or kill them or, indirectly, by destroying or degrading their habitat.

"Alien invasive species" means an alien species which becomes established in natural or semi-natural ecosystems or habitat, is an agent of change, and threatens native biological diversity.

"Alien species" (non-native, non-indigenous, foreign, exotic) means a species, subspecies, or lower taxon occurring outside of its natural range (past or present) and dispersal potential (i.e. outside the range it occupies naturally or could not occupy without direct or indirect introduction or care by humans) and includes any part, gametes or propagule of such species that might survive and subsequently reproduce.

The World Conservation Union (IUCN), states that the impacts of alien invasive species are immense, insidious, and usually irreversible. They may be as damaging to native species and ecosystems on a global scale as the loss and degradation of habitats. Although in the past many losses have gone unrecorded, we know that hundreds of extinctions have been caused by alien invasives. The ecological cost is the irretrievable loss of native species and ecosystems. Growing global trade and communication are directly contributing to the mixing of wildlife across biogeographical boundaries. (WWF, 2005)

This process, together with habitat destruction, has been a major cause of extinction of native species throughout the world in the past few hundred years (WWF,2005). Invasive alien species have been identified as a major threat faced by globally threatened birds and amphibians affecting 30% and 11% of threatened species (326 and 212 species respectively) and 8% of the 760 threatened mammals for which data are available. Island species are particularly susceptible to invasive alien species because of their isolated evolutionary history, with 67% of oceanic-island globally threatened birds affected directly or indirectly by invasive species, compared to 17% on continental islands and just 8% on continents. This susceptibility is spectacularly illustrated by the demise of Polynesian Partulid snails. The much lower percentages of threatened mammals and amphibians affected by invasive alien species than birds are probably a reflection of the limited abilities of these groups to colonize oceanic islands (Baillie et al., 2004).

*Polynesian Rat (Rattus exulans)*
The Polynesian Rat is widespread throughout the Pacific and South-east Asia. They cannot swim over long distances and are therefore considered to be a significant marker of the human migrations across the Pacific, as the Polynesians accidentally or deliberately introduced them to the islands they settled. There appear to be no island groups reached by the Polynesians that did not receive the Polynesian Rat, although not all islands in a group were necessarily colonised. Global Invasive Species Database Species Information.	Photographed by Michiel Broersen (2004). Polynesian Rats (Rattus exulans) in Parc de la Rivière Bleue, a National Park in New Caledonia. The Kagu (Rhynochetos jubatus), a New Caledonian bird, has proven vulnerable to introduced Polynesian and Black Rats, and is threatened with extinction. The Polynesian rat in the photos is radio tagged and marked to study their number and territory size.
*Black Rat (Rattus rattus)*
Global Invasive Species Database Species Information.
*Brown Rat (Rattus norvegicus)*
This rat is globally widespread and costs primary industry hundreds of millions of dollars per year. It has caused/contributed to the extinction/range reduction of native mammals, birds, reptiles and invertebrates through predation and competition. Global Invasive Species Database Species Information.
*Feral Goat (Capra hircus)*
Global Invasive Species Database Species Information.
Feral Pig (Sus scrofa)
Global Invasive Species Database Species Information.
*Feral Cat (Felis catus)*
Predation by feral cats has been directly resposible for numerous island extinction of mammals, reptiles and birds. On Macquarie Island, for example, feral cats caused the extinction of a subspecies of the red-fronted parakeet. On the mainland of Australia, they have probably contributed to the extinction of many small to medium sized mammals and ground-nesting birds in the arid zone, and seriously affected bilby, mala and numbat populations. In some instances, feral cats have directly threatened the success of recovery programs for endangered species. The Stephen Island Wren (Traversia lyalli), an extinct New Zealand bird, is a noteworthy example because the last population of this species was driven to extinction by one individual cat in 1894. Global Invasive Species Database Species Information.
*European Rabbit (Oryctolagus cuniculus)*
In Australia, rabbits are the most serious mammalian pests, an invasive species, and are responsible for the extinction of about as many native animals as the fox. Annually, European rabbits cause millions of dollars of damage to agriculture. In their natural environment and in captivity, rabbits are a benign, even useful species. However, when introduced by humans into environments that do not have natural defences against them, rabbits can cause enormous damage. Perhaps the most well-known example of this is the continent of Australia. Global Invasive Species Database Species Information.		Photo: wild European rabbits in Australia.
*Small Indian Mongoose (Herpestes javanicus)*
Mongooses still threaten endemic species on tropical cane growing islands. They have caused the population demise or extinction of many endemic vertebrates, continue to cause livestock damage and pose a disease risk. Global Invasive Species Database Species Information.
*Brown Tree Snake (Boiga irregularis)*
Native to eastern Indonesia, the Solomon Islands, New Guinea, as well as the northern and eastern coasts of Australia, the brown snake is notorious for concealing itself in international freight and aircraft. It is nocturnal, secretive and arboreal, hunting for food at all levels within a forest. The brown tree snake has altered the terrestrial ecology and disrupted the electrical supply of Guam. Global Invasive Species Database Species Information.
Photo: brown tree snake on a fence post in Guam. Photographed by Mark Kempen in 2003.
*Nile Perch (Lates niloticus)*
The Nile perch was introduced to Lake Victoria, in East Africa, in the 1960s, where it is fished commercially and has had a catastrophic effect on local fishes, causing the extinction of several hundred native species. Among the Lake Victoria population, 95 percent of the Nile perch's diet consists of native cichlids, at least half of whose species have been extirpated. The fish's introduction to Lake Victoria, while ecologically catastrophic, has been of short-term benefit to large fishing companies there. The long-term benefit is less clear, as overfishing is now reducing Nile perch populations there. The alteration of the native ecosystem has also had disruptive socio-economic effects on local communities in the countries bordering the lake. Large-scale fishing operations, while earning millions of dollars from their exported Nile perch catch, have displaced many local people from their traditional occupations in the fishing trade. In addition, the Nile perch's flesh, being oilier than that of the native fish species, is more difficult to dry. Consequently, the increased demand for firewood to dry the catch has contributed to deforestation of the surrounding region, resulting in pollution of the lake by runoff. The introduction of this species to Lake Victoria is one of the most commonly cited examples of the negative effects alien species can have on ecosystems and on the human populations which depend on them. Global Invasive Species Database Species Information.
*Rosy Wolf Snail (Euglandina rosea)*
The predatory "rosy wolf snail" (also known as the "cannibal snail") is native to the south-eastern United States, especially Florida. It has been introduced to islands in the Pacific and Indian Oceans, also to Bermuda and the Bahamas, as a putative biological control agent for another alien species, the giant African snail (Achatina fulica).	Rosy Wolf Snail (Euglandina rosea), Oahu, Hawaii. Photographed by Ron Heu, Hawaii Department of Agriculture.
This snail has caused the extinction of numerous endemic partulid tree snails in French Polynesia and has been heavily implicated in the extinction or at least decline of other species of snails wherever it has been introduced, notably in Hawaii. Global Invasive Species Database Species Information.

Biologists are investigating how these "invaders" succeed in establishing themselves in new environments, so that they can be controlled and eradicated where necessary. The United Kingdom for example successfully eradicated the Muskrat (Ondatra zibethicus) in 1935 and the Coypu or Nutria in 1987 (Myocastor coypus).

Baillie, J.E.M., Hilton-Taylor, C. and Stuart, S.N. (eds) 2004. 2004 IUCN Red List of Threatened Species. A Global Species Assessment. IUCN, Gland, Switzerland and Cambridge, UK. [PDF available via http://www.iucn.org/themes/ssc/red_list_2004/main_EN.htm].