Wildlife conservationists gained valuable knowledge when they sought to increase the wild populations of the endangered California condor and black-footed ferret through captive breeding and reintroduction into the wild.
Introduction, reintroduction, and translocation are old, well-established techniques for managing game and wild animal populations. Introduction involves placing animals in areas where they are not normally found, reintroduction is a means of restocking an area with animals that used to be there, and translocation involves moving animals from one part of their natural range to another. These techniques have traditionally been used for commercial, recreational, and management purposes, such as game ranching, game hunting and fishing, and controlling wild populations. Usually, the animals affected are wild specimens or semiwild, bred specimens of either game species or large populations of common (that is, nongame) species.
A California condor (identification tags on wings).
The reintroduction of captive-bred animals to prevent a species from becoming extinct is a technique that developed in the 1980’s and 1990’s from interdisciplinary studies in conservation management, small population and endangered species population biology, reproductive biology, wildlife veterinary medicine, genetics, and biotechnology. Unlike the older management techniques, this kind of reintroduction depends significantly on interagency cooperation, productive relationships with private landowners affected by the programs, and public support. In the early 1990’s, reintroduction of captive-bred animas was used successfully to prevent the California condor (Gymnogyps californianus) and the black-footed ferret (Mustela nigripes) from becoming extinct.
The California condor, whose nearest relative is the Andean condor of South America, belongs to the family of New World vultures. The bird’s habitat is the mountainous terrain surrounding the San Joaquin Valley. Los Angeles is at the southern boundary of the U-shaped range, and the San Francisco Bay Area is at its northern, coastal end. The condor population had decreased steadily since 1840, in part as a result of commercial and Indian ceremonial use of feathers, capture for sport and specimen collecting, wanton shooting and poisoning, and pollution. Primarily, however, the population had decreased as a result of the loss of habitat and food supply. In the early 1900’s, the population of California condors was about 150. Between 1920 and 1965, it dropped to 60, and by 1976, to 34.
The California Condor Recovery Plan was initiated in 1974 with the objective of maintaining at least 50 condors in the range they then inhabited. The plan eventually included the use of a captive propagation program begun by the U.S. Fish and Wildlife Service in 1976. Captive propagation of condors is somewhat problematic because the birds have a long period of sexual immaturity (they do not become mature until after the age of eight) and a low reproductive rate of at most one hatchling per year. The birds do well and breed successfully in captivity, however, and they are long-lived, living about twenty years in the wild and thirty-five to forty-five years in captivity. In addition, humans can encourage increased laying in captive birds by removing some of the eggs and hand-rearing the offspring.
It was believed that the wild population of condors had not had the capacity to increase significantly since the beginning of the twentieth century and that the bird was on the brink of extinction by 1974, when the recovery effort began. Despite this effort, the wild population declined further. By 1987, only 14 birds remained in the wild, and it was decided to place them in the captive propagation program, which at that time had 13 young hatchlings from eggs that had been removed from nests in the wild. The 27 birds were held in the San Diego and Los Angeles zoos. By 1990, this captive population had increased to 19 males and 21 females, and in 1991, the numbers had reached 26 males and 26 females. By 1992, an additional 12 juveniles had hatched. These birds began to be released back into the wild as of January, 1992.
The black-footed ferret is a small, nocturnal carnivore that depends on prairie dogs for 90 percent of its diet and shelter. Historically, its range extended throughout the western states, wherever the prairie dog lived. Like the prairie dog, the ferret lives in colonies and uses burrows for shelter. The decline of the black-footed ferret was the direct result of a decline in the prairie dog population, both being results of loss of habitat and of poisoning (the prairie dog was considered a pest and its burrows a hazard to free-ranging cattle). By 1980, the ferret’s habitat was so reduced and fragmented that extinction was thought likely to have occurred. When a Wyoming rancher’s dog caught a ferret in 1981, a search located a colony of the animals near Meeteetse.
From 1981 to 1984, researchers gathered biological and demographic data on the ferret population. By 1986, funding was obtained and a captive propagation facility established, and from 1985 to 1987, 18 specimens were captured and established at Sybille Wildlife Research Unit
This program also was successful. In 1987, 8 ferrets were born, of which 7 survived; in 1988, 44 were born, of which 34 survived; and in 1989, 80 were born, of which 58 survived. By 1991, the captive population had increased to 134. Shortly after the program got under way, an epidemic of canine distemper swept through the Meeteetse habitat, and by 1992 the prairie dog population there had declined by 90 percent and the ferret population was totally eradicated. For this reason, the release of captive ferrets, which began in the fall of 1991, was conducted not in Meeteetse but in southeastern Wyoming, near Shirley Basin and Medicine Bow.
The reintroduction programs for the California condor and the black-footed ferret serve as models for bringing other species back from the brink of extinction. From fewer than a couple dozen condors, the population in the wild had risen to about 200 by 2006, as the captive-bred birds had begun to reproduce in the wild. Similarly, the black-footed ferret population in the wild had slowly built up to about 500 by 2005. Although each species has its own requirements, the basic techniques and procedures used for the condor and ferret programs are widely applicable.
Analysis of efforts that fail can also be useful to future programs, as can examination of successful programs for areas where improvements can be made. Evaluations of the condor and ferret programs showed the need for improved cooperation among the organizations involved, better procedures and management programs, and more effective captive breeding programs. Above all else, the evaluations highlighted how crucial it is that the probability of the extinction of a species be determined before the population becomes too small to be able to respond.
With regard to the use of captive-bred specimens in conservation efforts, a number of programs have been established by the American Zoo and Aquarium Association
One aspect of modern captive propagation that may prove to be of particular value is the use of biotechnology. Many newly developed reproductive techniques may be used to increase numbers of offspring in endangered species and to improve the success of reproduction. Improvements in knowledge of genetics (both at the individual level and the population level), small population biology, veterinary medicine, and animal management are also expected to contribute to the success of propagation programs.
Continued and improved cooperation among federal and state governments, zoological parks, and the private sector is important to the design, planning, and implementation of effective conservation programs. This is particularly true for reintroduction programs for species that the public may consider dangerous or that private landowners wish to keep off their property. This was certainly the case with the black-footed ferret, which, along with its necessary food supply, the prairie dog, was considered a nuisance. To prevent species from going extinct, human beings must integrate their own interests with the preservation of suitable natural habitat and must use all available biotechnology techniques and biological knowledge.
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Beck, B. B., L. G. Rapaport, M. R. Stanley Price, and A. C. Wilson. “Reintroduction of Captive-Born Animals.” In Creative Conservation: Interactive Management of Wild and Captive Animals, edited by P. J. S. Olney, G. M. Mace, and A. T. C. Feistner. New York: Chapman & Hall, 1994. Presents a general overview of reintroduction as a conservation strategy and discusses the extent of the use of captive-born specimens in reintroduction programs. -
Godbey, Jerry, and Dean Biggins. “Recovery of the Black-Footed Ferret: Looking Back, Looking Forward.” Endangered Species Technical Bulletin 19, no. 1 (1994): 10, 13. Briefly reviews the effort to save the black-footed ferret. -
Nielsen, John. Condor: To the Brink and Back—The Life and Times of One Giant Bird. New York: HarperCollins, 2006. An environmental journalist relates the condor’s story. Includes extensive discussion of the at-time controversial captive-breeding program. -
Seal, Ulysses S., E. Tom Thorne, Michael A. Bogan, and Stanley H. Anderson, eds. Conservation Biology and the Black-footed Ferret. New Haven, Conn.: Yale University Press, 1989. Collection of essays discusses all aspects of the effort to save the black-footed ferret. Also includes several chapters on the captive propagation program. -
Snyder, Noel, and Helen Snyder. The California Condor: A Saga of Natural History and Conservation. Princeton, N.J.: Princeton University Press, 2000. Comprehensive volume discusses condor biology, nesting characteristics, and breeding behavior as well as conservation efforts and the controversies they have raised. Includes photographs, bibliography, and index. -
Thorne, E. Tom, and Bob Oakleaf. “Species Rescue for Captive Breeding: Black-Footed Ferret as an Example.” In Beyond Captive Breeding: Re-introducing Endangered Mammals to the Wild, edited by J. H. W. Gipps. London: Zoological Society of London, 1991. Reviews the black-footed ferret program as a case study in the development of captive-bred reintroduction programs. -
World Zoo Organization et al. The World Zoo Conservation Strategy: The Role of the Zoos and Aquaria of the World in Global Conservation. Chicago: Chicago Zoological Society, 1993. A global plan used as a guide for zoological parks, aquariums, wildlife agencies, and conservation organizations. Discusses how zoological parks and aquariums can make contributions to the overall wildlife conservation effort.
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