Reintroduction is an attempt to establish a species in an area which was once part of its historical range, but where it has become extinct. The source of animals used are either captive bred or translocated individuals. Translocation is the deliberate and mediated movement of wild individuals or populations from one part of their range to another. Reinforcement or supplementation is the addition of individuals to an existing population of conspecifics (i.e. those of same species).
Well known reintroduction / reinforcement projects include the golden lion tamarin Leontopithecus rosalia where zoo bred animals were reintroduced into the Atlantic rainforest of Brazil to supplement the endangered wild population; the Arabian oryx Oryx leucoryx which was extinct in the wild, but reintroduced into reserves in Oman from a previously established captive population, and the Californian condor Gymnogyps californianus which was subject to a breeding and reintroduction programme initiated in 1992. Other useful examples include Przewalski's horse Equus Ferus przewalskii, European bison Bison bonasus, Waldrapp ibis Geronticus eremita, European mink Mustela lutreola, common dormouse Muscardinus avellanarius (into UK), Mallorcan midwife toad Alytes muletensis, British field cricket Gryllus campestris and the Scimitar horned oryx Oryx dammah.
Reintroduction can be a valuable conservation tool, and there are a number of exciting and successful projects in which zoos have played an important role. However reintroduction is not the primary aim of conservation breeding in the majority of cases. Reintroductions tend to be very expensive, complicated and are frequently unsuccessful, although success increases with time as problems are rectified. For example, survival techniques, which are normally passed from parents to offspring during parenting, can often be lost, thus reintroduction programmes have to be planned carefully, ensuring that the animals have the necessary skills to survive. This may involve pre-release training in antipredator response, and avoiding imprinting by disguising keepers as members of the same species.
The aim of any reintroduction should be to establish a viable, free-ranging population in the wild, of a species that has become either globally or locally extinct. It should be reintroduced within the species’ former natural habitat and range and should require minimal long-term management. Socio-economic and legal requirements are important and the proposed project needs to be fully understood, accepted and supported by local communities. Policy, legislation, regulations and permits must all be in place before a project starts and the project must be with full permission and involvement of the recipient or host country government agencies.
The release animals
Suitable release stock is ideally translocated wild stock from a population where their removal will not jeopardise the source population. If release animals are to come from captive stock, they must come from a population that has been soundly managed both demographically and genetically.
With specific reference to captive stock, individuals should be given the opportunity to acquire the necessary information to enable survival in the wild. This includes fitness levels. Dangerous captive bred animals should not be so confident in the presence of humans that they might be a danger to local habitants or their livestock. Captive stock must not be reintroduced just because it is there or as a means of disposing of surplus stock.
Stock should undergo a thorough veterinary screening process before even being moved to the release site/country. It must always be remembered that once a wild animal has been released into the wild, it is very rarely possible to recover it or the potential pathogens it may be carrying or have carried.
The IUCN Reintroduction Specialist Group (RSG) have produced Guidelines for Reintroduction. These guidelines which were developed in response to the increasing occurrence of re-introduction projects worldwide, and consequently, to the growing need for specific policy guidelines to help ensure that the reintroductions achieve their intended conservation benefit, and do not cause adverse side-effects of greater impact. The Guidelines on Reintroductions together with the IUCN Policy Statement on the Translocation of Living Organism, IUCN Guidelines on the Placement of Confiscated Animals, Re-introduction NEWS, taxon and species specific reintroduction guidelines amongst many other documents are available on the IUCN CBSG website.
For health screening protocols see Quarantine and Health Screening Protocols for Wildlife Prior to Translocation and Release in to the Wild.
There are several over-view papers looking at what aspects of reintroduction works and why many have failed. These can be very useful when looking at a particular project. Google Scholar© is an excellent place to find references and often provides the abstract, if not the whole paper.