Captive propagation and reintroduction

Captive propagation is the deliberate breeding of wild animals in captivity in order to increase their numbers. Reintroduction is the deliberate release of these species into their native habitat . The Mongolian wild horse, Pere David's deer, and the American bison would probably have become extinct without captive propagation. Nearly all cases of captive propagation and reintroduction involve threatened or endangered species . Zoos are increasingly involved in captive propagation, sometimes using new technologies. One of these, allows a relatively common species of antelope to act as a surrogate mother and give birth to a rare species .

Once suitable sites are selected, a reintroduction can take one of three forms. Reestablishment reintroductions take place in areas where the species once occurred but is now entirely absent. Recent examples include the red wolf, the black-footed ferret , and the peregrine falcon east of the Mississippi River. Biologists use augmentation reintroduction to release captive-born wild animals into areas in which the species still occurs but only in low numbers. These new animals can help increase the size of the population and enhance genetic diversity. Examples include a small Brazilian monkey called the golden lion tamarin and the peregrine falcon in the western United States. A third type, experimental reintroduction, acts as a test case to acquire essential information for use on larger-scale permanent reintroductions. The red wolf was first released as an experimental reintroduction. A 1982 amendment to the Endangered Species Act facilitates experimental reintroductions, offering specific exemptions from the Act's protection, allowing managers greater flexibility should reintroduced animals cause unexpected problems.

Yet captive propagation and reintroduction programs have their drawbacks, the chief one being their high cost. Capture from the wild, food, veterinary care, facility use and maintenance all contribute significant costs to maintaining an animal in captivity. Other costs are incurred locating suitable reintroduction sites, preparing animals for release, and monitoring the results. Some conservationists have argued that the money would be better spent acquiring and protecting habitat in which remnant populations already live.

There are also other risks associated with captive propogation programs such as disease, but perhaps the greatest biological concern is that captive populations of endangered species might lose learned or genetic traits essential to their survival in the wild. Animals fed from birth, for example, might never pick up food-gathering or prey-hunting skills from their parents as they would in the wild. Consequently, when reintroduced such animals may lack the skill to feed themselves effectively. Furthermore, captive breeding of animals over a number of generations could affect their evolution . Animals that thrive in captivity might have a selective advantage over their "wilder" cohorts in a zoo , but might be disadvantaged upon reintroduction by the very traits that aided them while in captivity.

Despite these shortcomings, the use of captive propagation and reintroduction will continue to increase in the decades to come. Biologists learned a painful lesson about the fragility of endangered species in 1986 when a sudden outbreak of canine distemper decimated the only known group of black-footed ferrets. The last few ferrets were taken into captivity where they successfully bred. Even as new ferret populations become established through reintroduction, some ferrets will remain as captive breeders for insurance against future catastrophes. Biologists are also steadily improving their methods for successful reintroduction. They have learned how to select the combinations of sexes and ages that offer the best chance of success and have developed systematic ways to choose the best reintroduction sites.

Captive propagation and reintroduction will never become the principal means of restoring threatened and endangered species, but it has been proven effective and will continue to act as insurance against sudden or catastrophic losses in the wild.

See also Biodiversity; Extinction; Wildlife management; Wildlife rehabilitation

[James H. Shaw ]

RESOURCES

PERIODICALS

Jones, Suzanne R., ed. "Captive Propagation and Reintroduction: A Strategy for Preserving Endangered Species?" Endangered Species Update 8 (1) (1990): 1-88.

Lindburg, Donald G. "Are Wildlife Reintroductions Worth the Cost?" Zoo Biology 11 (1992): 1-2.