Bio Factsheet

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Number 208www.curriculum-press.co.uk

Captive breeding and the role of zoosMany animal species are threatened by habitat degradation,fragmentation and destruction. The complex causes of these arenot going to be addressed quickly enough to prevent some animalspecies becoming endangered or extinct.

The World Conservation Union (IUCN) estimate that only 3% ofthe planet is designated as a protected reserve and that, on average,one mammal, bird or reptile species has been lost each year for thelast 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 keepingsamples of species alive under varying degrees of captivity. Many‘zoos’ or animal collections in Britain have closed down, and manyhave tried to change the public perception of their activities bychanging their titles to, for example, ‘Wild Animal Parks’, but thefact remains that they have been accused of animal exploitation onthe 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 termsof their physical environment ( poor substrates in cages, forexample ) and their mental and social well-being ( limited feedingstimuli, or atypical social grouping )

• Capture of animals for exhibition may seriously deplete wildpopulations

• Re-introduction of species to the wild cannot be successful

Some of the arguments for and against the maintenance of animalcollections in ‘zoos’ are summarised in Box 1.

Breeding successes in captivity have increased in range andfrequency, partly because of:••••• environmental enrichment improving animals’ physical and

mental well-being, and their readiness to breed ( e.g. the socialgrouping of lowland gorillas in the John Aspinall wild animalparks in Kent has made them the most successful breedingcolony in the world )

• increased understanding of reproductive physiology ( e.g. anappreciation of oestrus cycles in rhinoceros has improvedbreeding success of both black and white rhinos at WhipsnadePark )

• the International Species Inventory System ( the Stud Books)set up at Minnesota Zoo and designed to reduce the geneticdangers of inbreeding (e.g. Arabian Oryx at Whipsnade andGolden Lion Tamarin at the Durrell Institute in Jersey havebenefited 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 habitatavailability makes breeding a reasonable proposition

••••• embryo transfer and surrogacy - involves obtaining ova froma captive female treated with reproductive hormones, fertilisingthese ova in vitro and implanting the resulting embryos into asurrogate mother of a closely-related but more common species

However, there are also difficulties..

The problems of captive breeding• The species must retain its ability to survive in its original habitat

and this becomes more unlikely the longer an individual is keptin captivity.

• Some aspects of behaviour are learned and some are innate.Advancing from primitive invertebrates to fish to reptiles tomammals, the proportion of learned behaviour increases. Thus,primates such as the Golden Lion Tamarin must be given theopportunity to spend time with and learn from experienced adultswhen they are young. If they are not given the opportunity tolearn 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 populationhas fallen to very low levels. The genetic diversity of the captivepopulation is therefore usually very low.

• Captive breeding is very expensive. Leader-Williams (1990)reports that the cost of keeping African elephants and Blackrhinos in captivity is 50 times that of maintaining equivalentpopulations in national parks in Zambia. In addition, he argues,money spent on captive breeding does nothing to help conservethreatened habitats and the many other species that live there.

Captive breeding and re-introductionis an example of ‘ex-situ’ conservationsince the species are being protectedoutside of their normal (‘wild’) habitat.‘In situ’ conservation – themanagement of species within theirnatural habitat is to be preferred, but ona worldwide scale it is thought that 800species of mammal, 800 species of bird,400 species of reptiles and amphibiansand as many as 80% of all Lake Malawicichlid species could disappear if therewere no captive breeding.

Box 1

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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 moreexcited by seeing lots of species rather than a lot of any one. Zoos that want breeding programmes must raise finance and this is whatprompts 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 breedingpopulations can be harmed if a competitor decides to use its profits in a price war (Fig. 1).

Zoo 1Usespopulationof animals togenerateprofit

Profitused toconserverarebreeds

VisitorschooseZoo 2moreoften

Profitsdecrease

Lessresources forbreeding.Thereforezoo considersreducingbreedingprogramme.

Zoo 2Uses populationof animals togenerate profit

Profitused toreduceentranceprice

Visitornumbersincrease

Profitsincrease

Fig. 1 Competition between zoos Critics of captive breeding in zoos also claim that, even if the breedingprogramme is a success, this may lead to more problems (Fig. 2).

Captivebreeding

Zoopopulationexceedscapacity

Circuses

Transfer to existing zoos

Build new zoos

Kill individuals

The main stages and problems involved in captive breeding areshown in Fig. 3

Fig. 2 Problems associated with captive breeding

Fig. 3 Stages and problems in captive breeding

Populationpressure

Habitat loss,degradation,fragmentation

Wildpopulationdecreases

Capture partof population

Breed Return towild

Points to considerCould it be reduced?

Establishreserve?

• How many?• Which

invertebrates/vertebrates –prebreeder orexperiencedbreeder?

• In existing zoo?• New zoo?• How to avoid inbreeding?• How to deliver appropriate

diet?• Encourage natural mating

or use artificial inseminationor embryo transplant?

• Captivity does not exert thesame selection pressure asin the wild.

• Imprinting on zoo keepers• Cost

Low survivalrates

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.

Much of the work on species preservation carried out in Britain is co-ordinated by BIAZA (British and Irish Association of Zoos andAquariums), 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 managementis the job of organisations such as BIAZA.

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www.curriculum-press.co.uk208. Captive breeding and the role of zoos

First made known to Western science in the 19th century, the only surviving herd was in a preservebelonging to the Chinese emperor. After the remaining population in China was lost the remaining deerin Europe were transported to England :The current population stems from this herd. Two herds of PèreDavid’s Deer were rentroduced to China in the late 1980s. In spite of the small population size, theanimals do not appear to suffer genetic problems.

The wild population in Mongolia died out in the 1960s; a program of exchange between captivepopulations in zoos throughout the world was started to reduce inbreeding. In 1992, sixteen horses werereleased into the wild in Mongolia, followed by additional animals later on. These reintroduced horsessuccessfully 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 Zoosuccessfully reversed a vasectomy on a Przewalski horse : scientists realized the animal in question wasone of the most genetically valuable Przewalski horses in the breeding programme.

Eliminated in the wild by hunting: restocked in Oman and Jordan from populations in London, Phoenixand San Diego zoos.

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 programmebegan at Durrell Wildlife preservation Trust - now up to 800 individuals in the wild.

Poipulation decline due to deforestation in western coastal forests of Brazil. In the 1970s the Braziliangovernment provided zoos with Golden Lion Tamarins which were successfully bred and disseminated tozoos around the world (especially jersey Zoo and Smithsonian Zoo in Washington, USA). Over the next 10years the government succeeded in establishing forest reserves in Brazil that allowed reintroduction of theTamarins. In this case then, the captive breeding programme effectively bought the time needed for theoriginal habitat to be conserved. There are now an estimated 1000 wild Tamarins and 600 in captivity.

Critically endangered by war and by bushmeat trade: breeding at Port Lympne Zoo in Kent has released intospecial reserves in the Gabon and the Congo. First ‘wild’ births to these reintroduced animals in 2008.

Captive breeding successes

Père David’s deer(Elaphurus davidianus)

Przewalski’s horse(Equus przewalskii)

Arabian oryx(Oryx leucoryx)

Mauritius kestrel(Falco punctatus)

Golden Lion Tamarin(Leontopithecus rosalia)

Lowland Gorilla(Gorilla gorilla gorilla)

Zoos And Conservation• how can zoos be justified?

Attraction to visitors• generates REVENUE which:

1. can be used to keep animals under optimum conditions2. can provide funding for academic research, particularly

into reproductive physiology and nutritional biology3. 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 )

ACADEMIC RESEARCH is carried out by many zoo-basedorganisations, e.g. the Royal Zoological Society of London (RZL ).e.g. reproductive physiology of the Asian rhinoceros gene-poolmake-up of the Arabian Oryx nutritional requirements of the GiantPanda

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 longperiods until breeding techniques are improved

Zoocheck: Campaigning group who lobby government to strengthen the 1981 UK Zoo Licensing Act. The Act presently emphasisessafety of public and zoo workers; Zoocheck want emphasis on animal welfare. Zoocheck would like most zoos to close and for themonies to be used to conserve habitats. They argue that zoos are an expensive waste of money, that most zoos do not containendangered species and that most endangered species are not represented in breeding programmes.

Captive breeding programmesform a part of the work of even the smallest zooe.g. Lowland Gorilla at Howlett’s Sumatran Rhino at Port Lympne,Cheetah at Whipsnade, Golden Lion Tamarin at Durrell InstituteJersey and, eventually, should lead to reintroduction to the wild

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 stimulationThus much current research centres on behavioural enrichment

• 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 forme.g. termite sticks, marmoset gum-trees

• Locomotory challenge : climbing animals such as Tamarins andmonkeys require “challenges”rather than “safe” substrates

• social stimuli : “calls” for Gibbons and Tamarins help themto develop social and hierarchical skills and someresearchers also recommend

• Selective challenges e.g. predators, severe climatic changes

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Conserving genetic diversity : The importance ofstudbooks

How genetic variation is lost. Genetic drift is a change in allelefrequencies over time. This may be simply due to chance, as insmall populations some alleles may not be passed on to offspring.

Fig 4: Genetic drift

T t

T t t S

t S

Tt tt

gametes

randomfertilisation

T, t and Sare alleles ofthe same gene

i.e. one allele maybe 'lost' fromthe gene pool

Genetic drift leads to a reduction in genetic variation.

Inbreeding depressionIn a small population, for example in captivity in a zoo or wild animalpark, there is an increased chance that closely-related individualswill mate (there simply aren’t so many partners to choose from).This inbreeding reduces the proportion of heterozygotes in thepopulation: there are more homozygous recessives as individualsreceive recessive alleles from both parents. Many recessive alleleshave harmful effects on the phenotype, so inbreeding depressionresults: the individuals are less reproductively ‘fit’. They may besmaller, less able to cope with disease and the females may producefewer eggs.

Conservation ‘in situ’ to maintain the size of wild populations is thebest way to prevent genetic drift and inbreeding depression.However, ‘ex situ’ conservation can play a part if the genetic historyof breeding individuals is known.

Keeping studbooks: Computer Dating for animals!Since animals were first domesticated, breeders would notedifferences between individuals and might use them selectively toimprove stock e.g. for milk yield, beef production or speed. Thefirst official studbook was the ‘General Studbook for ThoroughbredHorses, 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 arecooperating 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, birthdate, birth location, current location and transponder chipnumber.

Studbooks provide the raw data on which the breeding plans arebased: the plan must ensure

a. that genes from the original founder population (probably takenfrom the wild) are retained and are equally represented, so that

b. individuals that breed poorly in captivity must be encouragedto breed, and those that are particularly good breeders shouldbe limited in their breeding opportunities.

c. as a result of a. and b. the maximum genetic diversity, behaviouralcharacteristics and geographic origins are maintained.

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 bycontinually breeding the best breeders (and so reduced geneticdiversity)

2. this type of programme is almost the complete opposite ofartificial selection methods amongst domestic animals, in whichcertain characteristics are favoured even though these may beharmful to the animal in the wild (and so reduced geneticdiversity).

Case Study: Mauritius Kestrel

• Once widely distributed over theisland, the kestrel hunts in closedcanopy forest, feeding on geckos,large insects and small birds.

• Population decimated by forestdestruction for constructiontimber, fuelwood, food crops and, inthe 1950s and 1960s, by the use oforgano-chloride pesticides. Thespread of non–native plant species,introduced as seeds by other birds,also contributed to the decline of thenative 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 thePeregrine Fund. Captive breeding successfully carried outat Gerald Durrell Endemic Wildlife Sanctuary.

• Eggs taken from wild nests stimulated wild kestrels to laysecond clutch. The eggs that were removed were hatchedin incubators and hand reared.

• Some young kestrels were returned to the wild nest andadult birds reared them.

• Others were placed in artificial nest boxes and fed byhumans until they were old enough to hunt and avoidpredators. This allowed the breeders to exploit new, safeareas of forest.

• Over 400 kestrels have now been bred and released andthe wild-population now exceeds 800.

• Ironically, in 1994, a Mauritian kestrel ate a newly hatchedchick of a recently reintroduced pair of Mauritian pinkpigeons, the world’s rarest pigeon!

• The Mauritian kestrel is listed in Appendix 1 of CITES.Mauritian Kestrels can be seen at Chester Zoo, DurrellWildlife Preservation Trust, Jersey and Paignton Zoo.

• Websites:www.mauritian-wildlife.org and www.maurinet.com

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Case Study 4 : Ne-ne

There are those who believethat breeding animals incaptivity often results inbreeding them for captivity,and that reintroduction to thewild is rarely successful.

The Ne-Ne, or Hawaiian Goose (Branta sandvicensis) is oftenquoted as an example of the success of captive breedingtechniques, since a wild population which may have been aslow as 12 breeding pairs has been supplemented by more than3 000 captive-bred individuals.

The credit for this outstanding breeding programme is largelydue to the Wildfowl Trust in Slimbridge who developedtechniques in incubation, hatching and rearing of goose eggs,and who ensured the introduction of ‘wild genes’ from geesestill living in Hawaii.

Unfortunately, however, the reintroduction of Ne-Ne to Hawaiiand the neighbouring island has not yet been a completesuccess (captive bred animals are less successful at feedingthemselves, and at avoiding predators) but at least its status asa 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 thishabitat was ‘forced’ onto the Ne-Ne population, by pressuresfrom Humans and other animals, at just about the timeconservationists became aware of the declining numbers.

The case of the Ne-Ne does emphasise a most important point -reintroduction is unlikely to prove successful if the conditionswhich caused the animal to become endangered have remainedunchanged. Once again, the importance of conserving ahabitat as well as preserving a species is illustrated: ‘in situ’conservation and ex situ’ conservation are very closely linked.

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• Leader-Williams N et al (1990) Illegal exploitation of black

rhinoceros and elephant populations. J. Appl. Ecol 27:1055-1087

Key Words And Phrases

Captive Breeding The breeding of species in confinement, usually zoos, with the aim of reintroducing the animals back to theiroriginal habitat once it is safe to do so

CITES Convention for Trade in Endangered Species: controls the transfer of wildlife and wildlife products betweenmember countries

Endangered a species whose continued existence is deemed unlikely if the factors that are causing its decline continue e.g.Black rhinoceros

‘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 orNational park.

Inbreeding depression a reduction in reproductive fitness caused by matings between closely-related individuals (reducedheterozygosity)

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 breedingprogramme.

Translocation The release of animals taken from the wild into a new area in an attempt to re-establish or augment naturalpopulations.

Vulnerable A species which is likely to become endangered soon if the causes of its decline continue

Acknowledgements:This Factsheet was researched and written by Ron Pickering.Curriculum Press, Bank House, 105 King Street, Wellington, Shropshire, TF1 1NU.Bio Factsheets may be copied free of charge by teaching staff or students, provided that their school is a registeredsubscriber. No part of these Factsheets may be reproduced, stored in a retrieval system, or transmitted, in any otherform or by any other means, without the prior permission of the publisher. ISSN 1351-5136