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B io Factsheet www.curriculum-press.co.uk Number 208 Captive breeding and the role of zoos Many animal species are threatened by habitat degradation, fragmentation and destruction. The complex causes of these are not going to be addressed quickly enough to prevent some animal species becoming endangered or extinct. Breeding successes in captivity have increased in range and frequency, partly because of: • environmental enrichment improving animals’ physical and mental well-being, and their readiness to breed ( e.g. the social grouping of lowland gorillas in the John Aspinall wild animal parks in Kent has made them the most successful breeding colony in the world ) • increased understanding of reproductive physiology ( e.g. an appreciation of oestrus cycles in rhinoceros has improved breeding success of both black and white rhinos at Whipsnade Park ) • the International Species Inventory System ( the Stud Books) set up at Minnesota Zoo and designed to reduce the genetic dangers of inbreeding (e.g. Arabian Oryx at Whipsnade and Golden Lion Tamarin at the Durrell Institute in Jersey have benefited from contrived matings with distantly-related animals • the ‘frozen zoo’ concept - the maintenance of banks of sperm, ova and even embryos until such time as finance or habitat availability makes breeding a reasonable proposition • embryo transfer and surrogacy - involves obtaining ova from a captive female treated with reproductive hormones, fertilising these ova in vitro and implanting the resulting embryos into a surrogate mother of a closely-related but more common species The World Conservation Union (IUCN) estimate that only 3% of the planet is designated as a protected reserve and that, on average, one mammal, bird or reptile species has been lost each year for the last hundred years. Certain groups of species are particularly at risk – those with a restricted distribution, those of high economic value, those at the top of food chains and those in climax habitats. Zoos, or zoological gardens, are areas of confinement keeping samples of species alive under varying degrees of captivity. Many ‘zoos’ or animal collections in Britain have closed down, and many have tried to change the public perception of their activities by changing their titles to, for example, ‘Wild Animal Parks’, but the fact remains that they have been accused of animal exploitation on the grounds that: • Animals are exhibited on the basis of their ‘crowd-pulling’ power, rather than on their endangered status • Animals are kept under inappropriate conditions, both in terms of their physical environment ( poor substrates in cages, for example ) and their mental and social well-being ( limited feeding stimuli, or atypical social grouping ) However, there are also difficulties.. • Capture of animals for exhibition may seriously deplete wild populations The problems of captive breeding • • Re-introduction of species to the wild cannot be successful Some of the arguments for and against the maintenance of animal collections in ‘zoos’ are summarised in Box 1. • Box 1 Captive breeding and re-introduction is an example of ‘ex-situ’ conservation since the species are being protected outside of their normal (‘wild’) habitat. ‘In situ’ conservation – the management of species within their natural habitat is to be preferred, but on a worldwide scale it is thought that 800 species of mammal, 800 species of bird, 400 species of reptiles and amphibians and as many as 80% of all Lake Malawi cichlid species could disappear if there were no captive breeding. • • 1 The species must retain its ability to survive in its original habitat and this becomes more unlikely the longer an individual is kept in captivity. Some aspects of behaviour are learned and some are innate. Advancing from primitive invertebrates to fish to reptiles to mammals, the proportion of learned behaviour increases. Thus, primates such as the Golden Lion Tamarin must be given the opportunity to spend time with and learn from experienced adults when they are young. If they are not given the opportunity to learn that snakes or poisonous figs are dangerous, for example, their release into the wild could have negative consequences. Captive breeding often only begins when the wild population has fallen to very low levels. The genetic diversity of the captive population is therefore usually very low. Captive breeding is very expensive. Leader-Williams (1990) reports that the cost of keeping African elephants and Black rhinos in captivity is 50 times that of maintaining equivalent populations in national parks in Zambia. In addition, he argues, money spent on captive breeding does nothing to help conserve threatened habitats and the many other species that live there. Bio Factsheet 208. Captive breeding and the role of zoos www.curriculum-press.co.uk A zoo that wants to maintain a breeding population of, say, Mountain oryx, cannot just keep two or three animals. It will need to keep 30 – 50 and this is expensive. Unfortunately, the general public are unwilling to pay more to see 30 oryx than they are one or two; they are more excited by seeing lots of species rather than a lot of any one. Zoos that want breeding programmes must raise finance and this is what prompts zoos to charge each other for exchange or loan of animals. • The problem may be made worse because zoos are in competition. A zoo that uses its visitor profit to maintain captive breeding populations can be harmed if a competitor decides to use its profits in a price war (Fig. 1). Fig. 1 Competition between zoos Zoo 1 Uses population of animals to generate profit Zoo 2 Uses population of animals to generate profit Profit used to conserve rare breeds Visitors choose Zoo 2 more often Profit used to reduce entrance price Profits decrease Visitor numbers increase Critics of captive breeding in zoos also claim that, even if the breeding programme is a success, this may lead to more problems (Fig. 2). Less resources for breeding. Therefore zoo considers reducing breeding programme. Fig. 2 Problems associated with captive breeding Circuses Zoo population exceeds capacity Captive breeding Profits increase Transfer to existing zoos Build new zoos Kill individuals The main stages and problems involved in captive breeding are shown in Fig. 3 Fig. 3 Stages and problems in captive breeding Population pressure Points to consider Could it be reduced? Habitat loss, degradation, fragmentation Wild population decreases Establish reserve? Overall problems: • There are far more endangered species then can be saved by captive breeding. • Captive breeding reinforces species bias (in mammals, birds). • Ethical issues. Alternatives: • Cross-fostering eggs or young, translocation, habitat preservation, predator control. Breed Capture part of population • • How many? Which invertebrates/ vertebrates – prebreeder or experienced breeder? • • • • • • • • Return to wild Low survival In existing zoo? rates New zoo? How to avoid inbreeding? How to deliver appropriate diet? Encourage natural mating or use artificial insemination or embryo transplant? Captivity does not exert the same selection pressure as in the wild. Imprinting on zoo keepers Cost Much of the work on species preservation carried out in Britain is co-ordinated by BIAZA (British and Irish Association of Zoos and Aquariums), with its headquarters at Regent’s Park in London. The work of BIAZA can be accessed at www.biaza.org.uk. Key points in species management in zoos: • Zoos and aquariums cannot work in isolation, but must co-operate with one another. • Co-operation is essential if captive populations are to be successfully maintained without taking more individuals from populations in the wild. • Animals in separate zoos should be managed as part of one single population, and this population must have the greatest possible genetic variation. • Zoo managers must change their management strategy from keeping few individuals of a wide range of species (very popular with the fee-paying public) to keeping breeding groups of fewer species (often not so popular with the zoo accountants!) • It would be dangerous to keep all the individuals of one species in a single location: the entire population could be lost to disease or to a natural catastrophe. However, populations benefit genetically if they are managed as one single, global population. This management is the job of organisations such as BIAZA. 2 Bio Factsheet 208. Captive breeding and the role of zoos www.curriculum-press.co.uk Captive breeding successes Père David’s deer (Elaphurus davidianus) First made known to Western science in the 19th century, the only surviving herd was in a preserve belonging to the Chinese emperor. After the remaining population in China was lost the remaining deer in Europe were transported to England :The current population stems from this herd. Two herds of Père David’s Deer were rentroduced to China in the late 1980s. In spite of the small population size, the animals do not appear to suffer genetic problems. Przewalski’s horse (Equus przewalskii) The wild population in Mongolia died out in the 1960s; a program of exchange between captive populations in zoos throughout the world was started to reduce inbreeding. In 1992, sixteen horses were released into the wild in Mongolia, followed by additional animals later on. These reintroduced horses successfully reproduced, and the status of the animal was changed from “extinct in the wild” to “endangered” in 2005. In October, 2007 scientists at the Smithsonian Institution’s National Zoo successfully reversed a vasectomy on a Przewalski horse : scientists realized the animal in question was one of the most genetically valuable Przewalski horses in the breeding programme. Arabian oryx (Oryx leucoryx) Eliminated in the wild by hunting: restocked in Oman and Jordan from populations in London, Phoenix and San Diego zoos. Mauritius kestrel (Falco punctatus) Severe decline was in the 1950s and 1960s due to indiscriminate DDT use and invasive species like cats, mongooses and crab-eating macaques which killed the kestrels and their eggs. Breeding programme began at Durrell Wildlife preservation Trust - now up to 800 individuals in the wild. Golden Lion Tamarin (Leontopithecus rosalia) Poipulation decline due to deforestation in western coastal forests of Brazil. In the 1970s the Brazilian government provided zoos with Golden Lion Tamarins which were successfully bred and disseminated to zoos around the world (especially jersey Zoo and Smithsonian Zoo in Washington, USA). Over the next 10 years the government succeeded in establishing forest reserves in Brazil that allowed reintroduction of the Tamarins. In this case then, the captive breeding programme effectively bought the time needed for the original habitat to be conserved. There are now an estimated 1000 wild Tamarins and 600 in captivity. Lowland Gorilla (Gorilla gorilla gorilla) Critically endangered by war and by bushmeat trade: breeding at Port Lympne Zoo in Kent has released into special reserves in the Gabon and the Congo. First ‘wild’ births to these reintroduced animals in 2008. Zoocheck: Campaigning group who lobby government to strengthen the 1981 UK Zoo Licensing Act. The Act presently emphasises safety of public and zoo workers; Zoocheck want emphasis on animal welfare. Zoocheck would like most zoos to close and for the monies to be used to conserve habitats. They argue that zoos are an expensive waste of money, that most zoos do not contain endangered species and that most endangered species are not represented in breeding programmes. Zoos And Conservation Captive breeding programmes • form a part of the work of even the smallest zoo e.g. Lowland Gorilla at Howlett’s Sumatran Rhino at Port Lympne, Cheetah at Whipsnade, Golden Lion Tamarin at Durrell Institute Jersey and, eventually, should lead to reintroduction to the wild how can zoos be justified? Attraction to visitors • generates REVENUE which: 1. can be used to keep animals under optimum conditions 2. can provide funding for academic research, particularly into reproductive physiology and nutritional biology 3. might be used to pay for fieldwork and reserve management and may stimulate INTEREST and CONCERN (a) in conservation issues (b) in the “world of wildlife” ( > 50% of zoo visitors are children ) What about the animals? • they are usually well-fed and receive veterinary care so are longer-lived than wild relatives • they may suffer inapprpriate social grouping and limited sensory stimulation Thus much current research centres on behavioural enrichment ACADEMIC RESEARCH is carried out by many zoo-based organisations, e.g. the Royal Zoological Society of London (RZL ). e.g. reproductive physiology of the Asian rhinoceros gene-pool make-up of the Arabian Oryx nutritional requirements of the Giant Panda • Security : appropriate den/nestbox to act as a retreat • Species-specific behaviour : mud-baths for wallowing ( rhinos) deep litter for foraging (gorillas ) • Foraging : hiding food, or presenting it in a challenging form e.g. termite sticks, marmoset gum-trees • Locomotory challenge : climbing animals such as Tamarins and monkeys require “challenges”rather than “safe” substrates • social stimuli : “calls” for Gibbons and Tamarins help them to develop social and hierarchical skills and some researchers also recommend • Selective challenges e.g. predators, severe climatic changes Stud books and gene banks • • the family history of all captive animals can be compared so that matings between close relatives can be discouraged frozen sperm and/or embryos may be kept at - 197oC for long periods until breeding techniques are improved 3 Bio Factsheet 208. Captive breeding and the role of zoos www.curriculum-press.co.uk a. that genes from the original founder population (probably taken from the wild) are retained and are equally represented, so that b. individuals that breed poorly in captivity must be encouraged to breed, and those that are particularly good breeders should be limited in their breeding opportunities. c. as a result of a. and b. the maximum genetic diversity, behavioural characteristics and geographic origins are maintained. Conserving genetic diversity : The importance of studbooks How genetic variation is lost. Genetic drift is a change in allele frequencies over time. This may be simply due to chance, as in small populations some alleles may not be passed on to offspring. Fig 4: Genetic drift T gametes T t t t t random fertilisation Tt S S Two important points to note: 1. the modern approach is very different to that of zoo managers 50 years ago, who simply increased their stock of animals by continually breeding the best breeders (and so reduced genetic diversity) 2. this type of programme is almost the complete opposite of artificial selection methods amongst domestic animals, in which certain characteristics are favoured even though these may be harmful to the animal in the wild (and so reduced genetic diversity). T, t and S are alleles of the same gene i.e. one allele may be 'lost' from the gene pool Case Study: Mauritius Kestrel tt • Genetic drift leads to a reduction in genetic variation. • Inbreeding depression In a small population, for example in captivity in a zoo or wild animal park, there is an increased chance that closely-related individuals will mate (there simply aren’t so many partners to choose from). This inbreeding reduces the proportion of heterozygotes in the population: there are more homozygous recessives as individuals receive recessive alleles from both parents. Many recessive alleles have harmful effects on the phenotype, so inbreeding depression results: the individuals are less reproductively ‘fit’. They may be smaller, less able to cope with disease and the females may produce fewer eggs. • • Conservation ‘in situ’ to maintain the size of wild populations is the best way to prevent genetic drift and inbreeding depression. However, ‘ex situ’ conservation can play a part if the genetic history of breeding individuals is known. • • Keeping studbooks: Computer Dating for animals! Since animals were first domesticated, breeders would note differences between individuals and might use them selectively to improve stock e.g. for milk yield, beef production or speed. The first official studbook was the ‘General Studbook for Thoroughbred Horses, set up in England in 1791. Modern studbooks • are a collection of the genetic history and location of all the captive animals of a particular species in the collections that are cooperating in the overall breeding plan. • include data on the species’ status in the wild • usually include specialised software e.g. the ARKS (Animal Record Keeping System) includes species, sex, parents, birth date, birth location, current location and transponder chip number. • • • • • Studbooks provide the raw data on which the breeding plans are based: the plan must ensure 4 Once widely distributed over the island, the kestrel hunts in closed canopy forest, feeding on geckos, large insects and small birds. Population decimated by forest destruction for construction timber, fuelwood, food crops and, in the 1950s and 1960s, by the use of organo-chloride pesticides. The spread of non–native plant species, introduced as seeds by other birds, also contributed to the decline of the native forests. By 1974 only 6 birds remained, 2 of these were in captivity. Cooperation of Mauritius government, Jersey Wildlife Preservation Trust, Mauritian Wildlife Foundation and the Peregrine Fund. Captive breeding successfully carried out at Gerald Durrell Endemic Wildlife Sanctuary. Eggs taken from wild nests stimulated wild kestrels to lay second clutch. The eggs that were removed were hatched in incubators and hand reared. Some young kestrels were returned to the wild nest and adult birds reared them. Others were placed in artificial nest boxes and fed by humans until they were old enough to hunt and avoid predators. This allowed the breeders to exploit new, safe areas of forest. Over 400 kestrels have now been bred and released and the wild-population now exceeds 800. Ironically, in 1994, a Mauritian kestrel ate a newly hatched chick of a recently reintroduced pair of Mauritian pink pigeons, the world’s rarest pigeon! The Mauritian kestrel is listed in Appendix 1 of CITES. Mauritian Kestrels can be seen at Chester Zoo, Durrell Wildlife Preservation Trust, Jersey and Paignton Zoo. Websites:www.mauritian-wildlife.org and www.maurinet.com Bio Factsheet 208. Captive breeding and the role of zoos www.curriculum-press.co.uk Case Study 4 : Ne-ne Unfortunately, however, the reintroduction of Ne-Ne to Hawaii and the neighbouring island has not yet been a complete success (captive bred animals are less successful at feeding themselves, and at avoiding predators) but at least its status as a species has been ensured by the captive breeding programme. It seems that the habitat of the Ne-Ne (the slopes of volcanoes) is a difficult one for them to do well in: it is likely that this habitat was ‘forced’ onto the Ne-Ne population, by pressures from Humans and other animals, at just about the time conservationists became aware of the declining numbers. There are those who believe that breeding animals in captivity often results in breeding them for captivity, and that reintroduction to the wild is rarely successful. The Ne-Ne, or Hawaiian Goose (Branta sandvicensis) is often quoted as an example of the success of captive breeding techniques, since a wild population which may have been as low as 12 breeding pairs has been supplemented by more than 3 000 captive-bred individuals. The case of the Ne-Ne does emphasise a most important point reintroduction is unlikely to prove successful if the conditions which caused the animal to become endangered have remained unchanged. Once again, the importance of conserving a habitat as well as preserving a species is illustrated: ‘in situ’ conservation and ex situ’ conservation are very closely linked. The credit for this outstanding breeding programme is largely due to the Wildfowl Trust in Slimbridge who developed techniques in incubation, hatching and rearing of goose eggs, and who ensured the introduction of ‘wild genes’ from geese still living in Hawaii. Key Words And Phrases Captive Breeding The breeding of species in confinement, usually zoos, with the aim of reintroducing the animals back to their original habitat once it is safe to do so CITES Convention for Trade in Endangered Species: controls the transfer of wildlife and wildlife products between member countries a species whose continued existence is deemed unlikely if the factors that are causing its decline continue e.g. Black rhinoceros Endangered ‘Ex situ’ conservation Maintaining species outside their natural environment, in zoos or wildlife sanctuaries. Extinct A species for which there has been no confirmed sighting for 50 years. Genetic diversity Maintaining the range of alleles present in the wild (founder) population. ‘In situ’ conservation Maintaining species in their natural environment. This may include management of a Nature Reserve or National park. Inbreeding depression a reduction in reproductive fitness caused by matings between closely-related individuals (reduced heterozygosity) IUCN International Union for the Conservation of Nature and Natural Resources Rare A species with localised distribution but in no immediate danger Red Data Book List of all those species at risk: includes categories such as ‘vulnerable’, ‘at risk’, ‘rare’, endangered’ or ‘critically endangered’. An international register that is updated every three years Stud Book Awritten record (now computerised)of the genetic status and location of all of the individuals in a breeding programme. Translocation The release of animals taken from the wild into a new area in an attempt to re-establish or augment natural populations. Vulnerable A species which is likely to become endangered soon if the causes of its decline continue Useful sources of information • • • • • • Captive species breeding group of World Conservation Union (IUCN) www.cbsg.org Under “Reports” you can download summaries of management action plans for species and habitats www.iucn.org for news, campaigns and management plans for habitats and species such as the black rhino World Zoo Conservation strategy International Zoo News www.zoonews.ws Lots of interesting articles Reintroduction of Californian Condors www.sandiegozoo.org Acknowledgements: This Factsheet was researched and written by Ron Pickering. Leader-Williams N et al (1990) Illegal exploitation of black Curriculum Press, Bank House, 105 King Street, Wellington, Shropshire, TF1 1NU. Factsheets may be copied free of charge by teaching staff or students, provided that their school is a registered rhinoceros and elephant populations. J. Appl. Ecol 27:1055-1087 Bio subscriber. No part of these Factsheets may be reproduced, stored in a retrieval system, or transmitted, in any other form or by any other means, without the prior permission of the publisher. ISSN 1351-5136 5