by Graeme Gissing, Science Writer
As increasing pressures on wild populations result in dramatic declines in global biodiversity, captive breeding programs (CBPs) have become increasingly important components of species-specific conservation strategies.
Accordingly, the mandate of many modern zoos has shifted significantly from one of merely storehousing animals for public exhibition to being actively engaged in conservation education, research, and the ex-situ (captive) propagation of endangered species.
Ultimately, the goal of any CBP should be the reintroduction of individuals to either re-establish extirpated wild populations or to bolster numbers in existing wild populations.
There is clear evidence that, when successful, such programs play a direct and significant role in preventing short-term extinctions.
For example, the Arabian oryx (Oryx leucoryx) formerly ranged throughout much of the Arabian Peninsula but had, by the 1970s, become extinct in the wild. Through the implementation of CBPs and subsequent reintroductions, this species made a remarkable recovery resulting in a wild population of over 1000 individuals.
Another species saved from the brink of extinction is the California condor (Gymnogyps californianus). Almost wiped out by the destruction of habitat, poaching, and lead poisoning, the wild population was reduced to only 22 individuals by 1982. To save this species from extinction, the U.S. Fish and Wildlife Service made a bold and highly controversial decision to capture all remaining wild individuals. By 2016, after decades of dedicated captive management, the wild condor population had reached 276 individuals, and this captive breeding program remains one of the best examples of the potential for this conservation strategy.
Rather than as a conservation panacea for species recovery, CBPs should be weighed against their potential costs and significant challenges. For example, whereas the capture of wild California condors was used to successfully establish captive breeding colonies, other attempts have been far less successful.
Moreover, some have resulted in significant, though unintended consequences. The tragic case of a recent attempt to initiate a captive breeding program in the vaquita (Phocoena sinus) serves as a stark reminder of such risks.
Due mainly to entanglement in both legal and illegal fishing nets, the vaquita is currently the world’s most endangered marine mammal with as few as 30 individuals remaining in the wild. In 2017, as a last-ditch effort to save this species, an attempt was made to initiate a breeding program by capturing wild vaquitas. Two were successfully captured, but within hours the scenario turned bleak with both a juvenile and adult female showing signs of stress. Whereas the young vaquita was successfully released, the condition of the female continued to deteriorate. She died shortly after being released. A truly tragic end to a well-intentioned conservation effort.
Even with the potential risks, CBPs can be an essential component of a conservation plan, particularly for critically endangered species. Therefore, husbandry managers take significant efforts to maximize the chance of success by considering everything from genetics to animal welfare.
For example, to avoid unintended domestication in captive animals, enrichment strategies such as the use of semi-wild habitats can be used to mimic natural settings.
Other strategies include the exposure of captive populations to stimuli that mimic wild conditions such as sounds and scents of conspecifics or other animals of the same species, predators, or prey.
Equally important, from both a conservation and animal welfare perspective, is the psychological health of the animal. This concern requires the use of techniques that stimulate healthy and natural behaviors.
Well planned CBPs also provide unique opportunities to manage the potential fitness of offspring using detailed ancestry maps or “pedigrees” to maximize genetic diversity and avoid the harmful effects of inbreeding. Maximizing genetic diversity is particularly crucial for reintroduction programs as it increases the ability of individuals and populations to adapt to environmental change once reintroduced to the wild.
To maximize the chance of success, CBPs require careful planning to promote animal welfare, maintain wild traits and genetic diversity, and improve the likelihood that reintroduced animals will thrive in the wild. However, due to their high operating costs, it is essential that such programs do not unintendedly divert valuable resources away from more substantial ecosystem-level protection and habitat conservation efforts.
Ultimately, CBPs should be viewed as a vital component of a broader, more holistic approach to species recovery and be accompanied by the effective elimination of the drivers which caused a species’ decline. Without such an approach, captive breeding programs may be unintentionally creating an ark of last resort with limited potential to successfully repopulate wild spaces.
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