19 Demographic and Genetic Management of Captive Populations Jonathan D. Ballou, Caroline Lees, Lisa J. Faust, Sarah Long, Colleen Lynch, Laurie Bingaman Lackey, and Th omas J. Foose (deceased) viduals of the species, they represent the total genetic future of INTRODUCTION their species (e.g. black- footed ferrets). Unfortunately, captive Th e purpose of population management is to ensure that breeding programs are oft en initiated with few founders, com- populations of species of our choosing are available, healthy, promising the genetic health of the program from the start. and viable for the foreseeable future. Th us, the contribution Basic husbandry knowledge may also be lacking, so the popu- of zoos to ex situ conservation via captive breeding programs lation initially remains small, further compromising the ge- requires prudent population management planning. Popula- netic health of the population. Lack of reproduction may even tion management does result in successful conservation. Th e cause the population to go extinct (e.g. several species of Ha- rescue from extinction of species like the black- footed ferret, waiian birds). As knowledge is gained, reproduction becomes Mustela nigripes, California condor, Gymnogyps californianus, more reliable, generating the population’s growth phase. Popu- Guam rail, Rallus owstoni, Lord Howe Island woodhen, Gal- lation managers will set a target size for the population based lirallus sylvestris, greater stick- nest rat, Leporillus conditor, on resources available, the genetic and demographic status and mala, Lagorchestes hirsutus, testifi es to the potential of of the population, and the captive breeding needs of similar the international zoo community’s response to the needs of species competing for limited captive resources. Th e popula- species under the imminent threat of extinction. Successful tion will be maintained during the management phase at zero reintroduction of captive- born individuals into the wild to population growth to establish a stable population. And for reestablish natural free- ranging populations of golden lion certain populations, reintroduction of individuals into the wild tamarins, Leontopithecus rosalia, black- footed ferrets, Prze- may be an option (see Earnhardt, chap. , this volume). walski’s horses, Equus caballus przewalskii, chuditchs, Dasyu- Th e overall demographic goal for captive populations is rus geoff royii, and greater bilbies, Macrotis lagotis, is also a to increase the population, as rapidly as possible, to a suf- testament to the direct role of zoos in conservation. All these fi cient size to avoid extinction due to accidental or chance programs and more refl ect the implementation of successful events, and then to maintain that population with an age population management programs. and sex structure that promotes reliable reproduction when Th e World Zoo and Aquarium Conservation Strategy de- needed (and possible surplus reproduction for a reintroduc- veloped by the World Association of Zoos and Aquariums tion program). Th e demographic challenges here are to main- (WAZA ) recognizes this need and calls for increased tain stable populations that neither overshoot the capacity attention to and implementation of animal management at available, nor leave zoos with empty exhibits. the population level, and the establishment of truly viable Th e genetic goal for these populations is to retain the populations. Th is is both a biological and an organizational founders’ genetic diversity, as unchanged as possible over challenge. time, so that the population can serve as a genetic reservoir Some of the biological challenges are illustrated in fi gure for the species (from which genetic diversity may be reintro- ., which shows a hypothetical, but not atypical, history of duced into the wild). Achieving this goal means confronting a population rescued by captive breeding. Th e original wild the challenges of loss of genetic diversity, inbreeding and in- population may have declined for any number of reasons— breeding depression, and adaptation to captivity (Bryant and habitat loss, competition with invasive species, or disease. Reed ; Frankham, Ballou, and Briscoe ). Manage- Some or all of the few remaining wild- born individuals may ment strategies attempt, as much as possible, to retain every be captured to establish the captive breeding program in the aspect of the genetic diversity of the founders over time: es- founding phase. If these founders are the last remaining indi- sentially stopping evolution in the captive population. 219 220 demographic and genetic management of captive populations Wild Captivity Reintroduction stitutions, stress on animals). However, its benefi ts are clear, and are delineated in the rest of this section. management h t w o INCREASING VALUE TO CONSERVATION gr founding Intensive management can help populations to retain the ge- netic characteristics of wild counterparts. Th is increases their value as genetic reservoirs for use in reintroduction, should Fig. 19.1. A hypothetical history of the events in a captive population. this be needed. ENSURING THE AVAILABILITY OF CAPTIVE ANIMALS Th ere are organizational challenges involved in managing groups of individual zoo collections as cross- institutional bi- Many captive populations that were once large and well dis- ological populations. Th e international zoo community has tributed have subsequently crashed, particularly populations responded to this additional responsibility by forming re- of small mammals and birds (Amori and Gippoliti ; fi g. gional zoo associations and programs to organize and coordi- .). Although there are many reasons why populations nate cooperative population management eff orts, e.g. Species crash, many do so because individual collections are not Survival Plan (SSP) of the Association of Zoos and Aquari- managed as an integrated population. Th e result is not hav- ums (AZA, based in the United States and Canada); Euro- ing specimens available when desired. For example, when the pean Endangered species Programme (EEP) of the European giraff e, Giraff a camelopardalis, SSP was changed to a Popu- Association of Zoos and Aquaria (EAZA); and the Austral- lation Management Plan (PMP) in , recommendations asian Species Management Program (ASMP) of the Austral- became voluntary rather than mandatory (PMP recommen- asian Regional Association of Zoological Parks and Aquaria dations are voluntary, as opposed to recommendations made (ARAZPA) (Shoemaker and Flesness ; see Allard et al., in a SSP). Over the next years, giraff es, representing over chap. , this volume; Bingaman Lackey, appendix , this half the giraff es shipped in North America, were transferred volume). However, plans based on the science of population out of the AZA population. Th is resulted in a waiting list of management do not always coincide with desires of individ- institutions wanting roughly giraff es; an additional ual institutions. More zoos may want to breed than is needed institutions wishing to build and stock new giraff e exhibits for zero population growth during the management phase. found few available. Ideal genetic management recommendations to transfer a particular animal to another zoo may confl ict with the hold- IMPROVING ANIMAL WELFARE ing zoo’s desire to keep that individual. Managers of captive breeding populations are continually struggling to balance Population management attempts to avoid inbreeding, as in- the science with institutional wishes. bred animals oft en suff er from a vast assortment of ailments. Th is chapter does not address the sometimes competing Th ese include reduced longevity, inanition (failure to thrive), needs of population management versus institutional wishes. metabolic diseases, morphological deformities, abnormal Rather, it presents and outlines the basic principles, concepts, birth weights and growth, organ (eye, brain, spleen, adrenal and techniques that are involved in managing captive popula- gland, thyroid) malformations, impaired reproductive traits, tions, concentrating on those aspects critical to the long- term maintenance of genetic diversity and demographic security 250 (Ballou and Foose ). Th e chapter begins with the basic data needed for a management plan, followed by a description Kowari Elephant shrew 200 of the overall purpose and goals of the captive population. Patagonian cavy We present the demographic and genetic characteristics that Tree shrew are used to defi ne the current status of a population, followed 150 by a description of the basic management strategies that are applied to population management and a description of the more detailed analyses that form the basis of the individual- 100 by- individual animal recommendations—the heart of any Population size population management plan. We end by addressing par- 50 ticularly diffi cult issues (how to proceed when data are poor and how to manage groups of individuals where individual identity is not known). 0 1970 1975 1980 1985 1990 1995 2000 2005 Year THE VALUE OF POPULATION MANAGEMENT Fig. 19.2. Captive population crashes and declines in 4 small mammal Managing captive populations is time consuming (maintain- species: kowari, Dasyuroides byrnei, elephant shrew, Macroscelides ing the data, making recommendations), costly (shipping proboscideus, Patagonian cavy, Dolichotis patagonum, and tree shrew, animals), and sometimes risky (disease transfer between in- Tupaia glis. ballou, lees, faust, long, lynch, bingaman lackey, and foose 221 modifi