Captive breeding, also known as captive propagation, is the process of plants or animals in controlled environments, such as wildlife reserves, zoos, botanic gardens, and other conservation facilities. It is sometimes employed to help species that are being threatened by the effects of human activities such as climate change, habitat loss, fragmentation, over hunting or fishing, pollution, predation, disease, and parasitism.
For many species, relatively little is known about the conditions needed for successful breeding. Information about a species' reproductive biology may be critical to the success of a captive breeding program. In some cases a captive breeding program can save a species from extinction, but for success, breeders must consider many factors—including genetic, ecological, behavioral, and ethical issues. Most successful attempts involve the cooperation and coordination of many institutions.
Captive breeding techniques began with the first human domestication of animals such as goats, and plants like wheat, at least 10,000 years ago.
The first actual captive breeding programs were only started in the 1960s. These programs, such as the Arabian Oryx breeding program from the Phoenix Zoo in 1962, were aimed at the reintroduction of these species into the wild. These programs expanded under The Endangered Species Act of 1973 of the Nixon Administration which focused on protecting endangered species and their habitats to preserve biodiversity. Since then, research and conservation have been housed in zoos, such as the Institute for Conservation Research at the San Diego Zoo founded in 1975 and expanded in 2009, which have contributed to the successful conservation efforts of species such as the Hawaiian Crow.
The breeding of species of conservation concern is coordinated by cooperative breeding programs containing international studbooks and coordinators, who evaluate the roles of individual animals and institutions from a global or regional perspective. These studbooks contain information on birth date, gender, location, and lineage (if known), which helps determine survival and reproduction rates, number of founders of the population, and inbreeding coefficients. A species coordinator reviews the information in studbooks and determines a breeding strategy that would produce most advantageous offspring.
If two compatible animals are found at different zoos, the animals may be transported for mating, but this is stressful, which could in turn make mating less likely. However, this is still a popular breeding method among European zoological organizations.
There are regional programmes for the conservation of endangered species:
- Americas: Canadian Association of Zoos and AquariumsCAZA)
- Europe: European Endangered Species Programme EEP (European Association of Zoos and AquariaEAZA)
- Australasia: Australasian Species Management Program ASMP (Zoo and Aquarium Association ZAA)
- Africa: African Preservation Program APP (African Association of Zoological Gardens and Aquaria PAAZAB)
- Japan: Conservation activities of Japanese Association of Zoos and Aquariums JAZA
- South Asia: Conservation activities of South Asian Zoo Association for Regional Cooperation SAZARC
- South East Asia: Conservation activities of South East Asian Zoos Association SEAZA
The objective of many captive populations is to hold similar levels of genetic diversity to what is found in wild populations. As captive populations are usually small and maintained in artificial environments, genetics factors such as adaptation, inbreeding and loss of diversity can be a major concern.
Adaptive differences between plant and animal populations arise due to variations in environmental pressures. In the case of captive breeding prior to reintroduction into the wild, it's possible for species to evolve to adapt to the captive environment, rather than their natural environment. Reintroducing a plant or animal to an environment dissimilar to the one they were originally from can cause fixation of traits that may not be suited for that environment leaving the individual disadvantaged. Selection intensity, initial genetic diversity, and effective population size can impact how much the species adapts to its captive environment. Modeling works indicate that the duration of the programs (i.e., time from the foundation of the captive population to the last release event) is an important determinant of reintroduction success. Success is maximized for intermediate project duration allowing the release of a sufficient number of individuals, while minimizing the number of generations undergoing relaxed selection in captivity. Can be minimized by reducing the number of generations in captivity, minimizing selection for captive adaptations by creating environment similar to natural environment and maximizing the number of immigrants from wild populations.
One consequence of small captive population size is the increased impact of genetic drift, where genes have the potential to fix or disappear completely by chance, thereby reducing genetic diversity. Other factors that can impact genetic diversity in a captive population are bottlenecks and initial population size. Bottlenecks, such as rapid decline in the population or a small initial population impacts genetic diversity. Loss can be minimized by establishing a population with a large enough number of founders to genetically represent the wild population, maximize population size, maximize ratio of effective population size to actual population size, and minimize the number of generations in captivity.
Inbreeding is when organisms mate with closely related individuals, lowering
Outbreeding is when organisms mate with unrelated individuals, increasing heterozygosity in a population. Although new diversity is often beneficial, if there are large genetic differences between the two individuals it can result in outbreeding depression. This is a reduction in fitness, similar to that of inbreeding depression, but arises from a number of different mechanisms, including taxonomic issues, chromosomal differences, sexual incompatibility, or adaptive differences between the individuals. A common cause is chromosomal ploidy differences and hybridization between individuals leading to sterility. The best example is in the orangutan, which, prior to taxonomic revisions in the 1980s would be commonly mated in captive populations producing hybrid orangutans with lower fitness. If chromosomal ploidy is ignored during reintroduction, restoration efforts would fail due to sterile hybrids in the wild. If there are large genetic differences between individuals originally from distant populations, those individuals should only be bred in circumstances where no other mates exist.
Captive breeding can contribute to changes in behavior in animals that have been reintroduced to the wild. Released animals are commonly less capable of hunting or foraging for food, which leads to
Salmon bred in captivity have shown similar declines in caution and are killed by predators when young. However, salmon that were reared in an enriched environment with natural prey showed less risk-taking behaviors and were more likely to survive.
A study on mice has found that after captive breeding had been in place for multiple generations and these mice were "released" to breed with wild mice, that the captive-born mice bred amongst themselves instead of with the wild mice. This suggests that captive breeding may affect mating preferences, and has implications for the success of a reintroduction program.
Human mediated recovery of species can unintentionally promote maladaptive behaviors in wild populations. In 1980 the number of wild Chatham Island Black Robins was reduced to a single mating pair. Intense management of populations helped the population recover and by 1998 there were 200 individuals. During recovery scientists observed "rim laying" an egg laying habit where individuals laid eggs on the rim of the nest instead of the center. Rim laid eggs never hatched. To combat this land managers pushed the egg to the center of the nest, which greatly increased reproduction. However, by allowing this maladaptive trait to persist, over half the population were now rim layers. Genetic studies found that this was an autosomal dominant mendelian trait that was selected for due to human intervention
The De Wildt Cheetah and Wildlife Centre, established in South Africa in 1971, has a cheetah captive breeding program. Between 1975 and 2005, 242 litters were born with a total of 785 cubs. The survival rate of cubs was 71.3% for the first twelve months and 66.2% for older cubs, validating the fact that cheetahs can be bred successfully (and their endangerment decreased). It also indicated that failure in other breeding habitats may be due to "poor" sperm morphology.
The Galápagos tortoise population, once reaching as low in population as 12 remaining individuals, was recovered to more than 2000 today by a captive breeding program. A further 8 tortoise species were supported by captive breeding programs in the island chain. 
To found a captive breeding population with adequate genetic diversity, breeders usually select individuals from different source populations—ideally, at least 20-30 individuals. Founding populations for captive breeding programs have often had fewer individuals than ideal because of their threatened state, leaving them more susceptible to challenges such as inbreeding depression.
To overcome challenges of captive breeding such as adaptive differences, loss of genetic diversity, inbreeding depression, and outbreeding depression and get desired results, captive breeding programs use many monitoring methods. Artificial insemination is used to produce the desired offspring from individuals who don't mate naturally to reduce effects of mating closely related individuals such as inbreeding. Methods as seen in panda pornography allow programs to mate chosen individuals by encouraging mating behavior. As a concern in captive breeding is to minimize the effects of breeding closely related individuals, microsatellite regions from an organisms genome can be used to determine amounts of relationship among founders to minimize relatedness and pick the most distant individuals to breed. This method has successfully been used in the captive breeding of the California condor and the Guam rail. The maximum avoidance of inbreeding (MAI) scheme allows control at a group level rather than an individual level by rotating individuals between groups to avoid inbreeding.
Assisted reproduction technology (ART): Artificial insemination
Getting captive wild animals to breed naturally can be a difficult task. Giant pandas for example lose interest in mating once they are captured, and female giant pandas only experience estrus once a year, which only lasts for 48 to 72 hours. Many researchers have turned to artificial insemination in an attempt to increase the populations of endangered animals. It may be used for many reasons, including to overcome physical breeding difficulties, to allow a male to inseminate a much larger number of females, to control the paternity of offspring, and to avoid injury incurred during natural mating. It also creates more genetically diverse captive populations, enabling captive facilities to easily share genetic material with each other without the need to move animals. Scientist of the Justus-Liebig-University of Giessen, Germany, from the working group of Michael Lierz, developed a novel technique for semen collection and artificial insemination in parrots producing the world's first macaw by assisted reproduction
Animal species can be preserved in
An example of the use of cryoconservation to prevent the extinction of a livestock breed is the case of the
The best current cloning techniques have an average success rate of 9.4 percent,
A potential technique for aiding in reproduction of endangered species is interspecific pregnancy, implanting embryos of an endangered species into the womb of a female of a related species, carrying it to term. It has been used for the Spanish Ibex and Houbara bustard.
With successes, captive-breeding programs have proven successful throughout history. Notable examples include the American
While captive breeding sounds like an ideal solution for preventing endangered animals from facing serious threats of extinction there are still reasons to believe that these programs can occasionally do more harm than good. Some detrimental effects include delays in understanding optimal conditions required for reproduction, failure to reach self-sustaining levels or provide sufficient stock for release, loss of genetic diversity due to inbreeding, and poor success in reintroductions despite available captive-bred young. Although it has been proven that captive breeding programs have yielded negative genetic effects in decreasing the fitness of captive-bred organisms, there is no direct evidence to show that this negative effect also decreases the overall fitness of their wild-born descendants.
There is reason to demand for the release of animals from captivity programs for four main reasons: a lack of sufficient space due to overly successful breeding programs, closure of facilities due to financial reasons, pressure from animal rights advocacy groups, and to aid the conservation of endangered species. Additionally, there are many ethical complications to reintroducing animals born in captivity back into the wild. For example, when scientists were reintroducing a rare species of toad back into the Mallorcan wild in 1993, a potentially deadly fungus that could kill frogs and toads was unintentionally introduced. It is also important to maintain the organism’s original habitat, or replicate that specific habitat for species survival.
- Breeding in the wild
- European Endangered Species Programme(EEP)
- Ex-situ conservation
- Panda pornography
- Species Survival Plan or SSP
- World Conference on Breeding Endangered Species in Captivity as an Aid to their Survival or WCBESCAS
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