What you propose has been done successfully with other species. The Laysan duck has been deliberately introduced to Midway Island for this purpose: http://64.233.167.104/search?q=cache:JeerLGFfs7EJ:www.hawaiianatolls.org/research/NWHIRAMP2004/features/laysan-ducks.php+%22lays

Early in the last century, China's Pere David's deer survived ONLY on the estate of the Duke of Bedford: http://library.thinkquest.org/5053/Asia/peredavid'sdeer.html

The Franklinia, a beautiful plant from the U.S. state of Georgia, was nearly extinct at the time of its discovery by Western science in 1765. The wild population did become extinct, but today you can buy a franklinia from your local nursery because it survived in a Philadelphia garden: http://www.bartramsgarden.org/franklinia/

Kent