endangered species

The Indian rhinoceros Rhinoceros unicornis, the largest of the Asiatic species, weighs up to two tons and has only one horn. Its skin is deeply creased at the neck, shoulders, and legs, resembling armour plating. Now restricted to areas of Nepal, Assam, and Bengal, the Indian rhinoceros, like nearly all rhinoceroses, is an endangered species.

A female one-horned Indian rhinoceros Rhinoceros unicornis. Rhinoceros favour grassy swampland and are solitary animals except when raising young. The single calf will remain with its mother for more than two years.

Grazing herd of African elephants, Kenya. The African elephant has been aggressively hunted for its ivory tusks and is now an endangered species.

Plant or animal species whose numbers are so few that it is at risk of becoming extinct. Officially designated endangered species are listed by the World Conservation Union (or IUCN).

An endangered species is not a new phenomenon; extinction is an integral part of evolution. The replacement of one species by another usually involves the eradication of the less successful form, and ensures the continuance and diversification of life in all forms. However, extinctions induced by humans are thought to be destructive, causing evolutionary dead ends that do not allow for succession by a more fit species. The great majority of recent extinctions have been directly or indirectly caused by humans, most often by the loss, modification, or pollution of the organism's habitat, but also by hunting for ‘sport’ or for commercial purposes.

According to the Red Data List of endangered species, published by the International Union for the Conservation of Nature (IUCN) in 2006, a total of 16,119 known species, including 25% of all mammal species and 12.4% of all bird species are threatened with extinction.

A quarter of the world's plants are in danger of becoming extinct by the year 2020. One-third of North American freshwater fish are threatened or endangered. Almost half of Australia's surviving mammals are threatened with extinction.

Of those species that changed status in the 2006 edition of the Red List, 172 declined and 139 improved.

An example of an endangered species is the Javan rhinoceros. There are only about sixty alive today, in Indonesia and Vietnam. Unless active steps are taken to promote its survival, this species will probably be extinct within a few decades.

In 2001, a cloned mouflon lamb was born in Sardinia, as part of a conservation strategy. It was the first endangered species to be successfully cloned.