The practice of ex-situ conservation involves techniques which are essentially mean to maintain, multiply or help the species to survive under natural conditions.
The method involves capture, maintenance and breeding in captivity on long term basis of individuals of the endangered species. Captive breeding and propagation on long term basis is usually under taken for species which have lost their habitats permanently or there are present certain such factors in the habitat which shall force it to extinction again. In majority of cases when human interests - such as poaching, excessive hunting etc. - come in direct conflict with existence^ the species long term maintenance and breading in captivity is resorted to.
Our zoos and botanical gardens house a number of such animals and plants which are regularly bred in captivity. Most of the species shall not survive in their wild habitats. Captive breeding and maintenance is the only way to preserve such species. There are many species of both plants and animals which occur in captivity under human care only.
An interesting case is that of Pere David's deer (Elaphurus davidianus) which is believed to have inhabited the alluvial plains of northern China, probably living in swampy reed covered localities. Rapid spread of agriculture and other human enterprises pushed it to extinction in the wild. A small herd was, however, maintained in Imperial Hunting Park in Peking, China.
It was from this herd that Abbe Armond David procurred a pair by bribing the sentinel. The last animal of the Imperial herd died in 1920. It is from Abbe Armond David's pair that the species survives today. Nearly 400 specimens of the species are in various zoos of the world where they are maintained and multiplied regularly. The species cannot survive in its original habitats in northern China which is now occupied by sprawling agricultural fields and industries.
Similarly Przewalski's Horse (Equus przewalskii) is regularly maintained and bred in captivity. All the specimens of the species now available are descendents of a few animals originally procured from Mongolian plains and kept in zoos of Munich and Prague. The animal once roamed all over the plains of Central Asia and Europe.
It was in 1950 that the specimens from Munich and Prague zoos were brought together and bred in captivity. There are about 500 animals of this wild species of horse in various zoos and reserves whereas the species has disappeared in the wild.
The story of the Siberian tiger (Panthera tigris altaica) and Addax (Addax nosomaculatus) is also similar, ft Siberian tiger, prized for its skin and bones is ruthlessly hunted by poachers while addax is sought for and hunted for its tasty flesh and hide in Sahelo-Sahara region.
Both animals fall an easy prey to Hunters - the Siberian tiger because of its pug-marks which are very conspicuous in snow and the addax because of its slower speed of movement. The population of both the species has been steadily declining in nature.
Though about 300 Siberian tigers still survive in nature, their fate can be judged by the fact that in 1992 alone, more than 65 animals were killed by poachers for their skin and bones. Addax had almost completely disappeared from its wild habitat when ex-situ conservation methods were resorted to by conservationists. Both Siberian tiger and addax are maintained and bred in captivity in various zoos and their population is now increasing. These animals shall be subjected to ruthless hunting again if introduced in their wild habitats and the species shall be lost.
Lion tailed macaque (Macaca silenus) is one of the world's most endangered Primates which survives in the ever-green forests of Western Ghats of South India with a population of about 500 individuals only. The animal is hunted for its tasty flesh and various body parts which are supposed to have medicinal value.
The population of this species which was once abundant has been steadily declining. It is feared that if something is not done the species shall become extinct in near future. Many specimens of this primate were, therefore, introduced in various zoos in India and are currently maintained and bred in captivity while in the wild there has been a faster decrease in their population. About 100 specimens of the species are present in various zoos in India (1995 figures).
There are a number of species which are being helped by ex-situ conservation technology, i.e., are being maintained and bred in captivity under human care while their original homes have been so changed that they cannot survive therein. These species include: Siberian tiger, Pere Davids deer, Lion tailed macaque, European bison, Przewalski's horse, Brown eared pheasant, Edwards' pheasant, Bali Myna, White naped crane, Addax, Slender horned gazelle, Scimitar horned oryx, Gaur, Grevy's Zebra, Puerto Rican horned toad, Chinese aligator, Mauritius pink pigeon, Madagasker radiated tortoise, Aruba island rattle snake etc.