474 Zoos and Zoological Parks As the supply of wild-born founders dwindles, and more amenities are expected for the animals in hand, zoos are abandoning the one-of-each-kind collecting approach Withinzoo species diversity is decreasing in order to make room for zoos to manage larger, more natural social groups and to house a breeding nucleus of at least several pairs and their young offspring of nonsocial species (Gibbons et al., 1995) Many zoos are trying to allocate a proportion of their animal space for off-exhibit breeding efforts, and some are operating special facilities devoted to breeding of endangered species – mostly ex situ but also some in situ Many zoos are developing specializations, concentrating their efforts on the specific groups of animals that they can keep best and exhibit most dramatically Zoo workers are also becoming more specialized, both along taxonomic lines and also professionally into fields such as educators, veterinarians, nutritionists, population biologists, behaviorists, life-support system operators, pathologists, and horticulturists With the increasing need for cooperation, more formal committees and other structures are developing through the professional organizations Choosing Animals to Promote Biodiversity Conservation the animals are under human care Arguably, this is a prudent and responsible strategy should the animals be needed someday for restocking wild habitats Habitats are also changing, so the theoretically successful genetic profile of the past might not be the same in the future By breeding for variability, i.e., retaining as much of variability as was present in the original wild-caught founders as possible, the potential for readaptation to old or new habitats is maximized Hence, zoo population plans usually strive to breed animals better than would be done randomly without a scientific framework, and they often try to this by maintaining small, well-managed populations that are projected to be genetically and demographically viable well into the future This usually requires a captive population of several hundred animals In this effort, attention must often be paid to picking the right unit for conservation, or the evolutionarily significant unit Zoos have funded a considerable amount of applied molecular genetic research in order to determine subspecies and species characteristics, thereby avoiding the possibility of breeding animals that are similar-looking but are in fact different species The converse is just as problematic when members of the same species are perceived as distinct and maintained separately, taking up valuable space and/or compromising the viability of both populations with suboptimal numbers Space, the Final Limit Modern zoos are expensive to build and upgrade In North America alone, zoos spend millions of dollars per year on capital or physical improvements, with much larger expenditures for major new exhibits or zoo facilities A major exhibit can cost in the tens of millions of dollars and typically takes at least years to plan and build Maintaining a zoo and its animals is also very expensive Therefore, there are practical limits to how many zoos can be supported and thus to how many animals can be maintained by zoos (Conway, 1986) For example, the number of animals that are presently kept in the 223 accredited zoos of North America is approximately 870,000 from among 6000 species Thus, conservation-oriented zoos choose their inhabitants with care in order to maximize the biodiversity that they preserve in their finite space A biodiversity trade-off must be made between the number of species that are maintained by zoos versus the genetic diversity or size of the captive populations that are maintained Zoo planners have to think longterm because they are trying to maintain viable populations for decades or centuries In many cases, zoo populations are, essentially, closed gene pools because it is difficult or impossible to acquire new lineages or wild-caught ‘‘founders.’’ Extinction in nature is the most obvious cause for a closed captive population, and zoos work with several ‘‘extinct’’ species such as the Prezwalski’s horse But species that are extant in nature can also be effectively isolated in zoos by government import or export regulations, concerns about disease transmission, rarity in nature, political issues, or the extreme difficulty and expense of collecting some species In most cases zoo planners also try to ‘‘save all the pieces’’ by managing their populations for genetic variability Genetic variability is an achievable objective since anything approaching natural selection is by definition impossible while Metamanagement of Zoo Biodiversity Each zoo is an island too small to much conservation breeding on its own To facilitate cooperation, organized conservation programs involving captive animals are beginning to develop around the world through regional zoo professional associations Most of the labor that goes into these programs is pro bono or volunteer Much of the work is accomplished through workshop meetings and via committee, at considerable personal and institutional expense The basic unit of these programs is the studbook, which is the database of historic and living animals in a particular captive population Studbooks are usually maintained through the efforts of one ‘‘studbook keeper.’’ Populations that are monitored with studbooks can be managed through regional or even global captive breeding plans, usually overseen by a committee, which specifies where each animal should be and whether it should be bred To prioritize how much captive space various populations should be allocated, zoo specialist groups for each kind of animal have formed, and are known as ‘‘taxon (for taxonomic) advisory groups.’’ Taxon advisory groups typically work closely with the appropriate taxonomic and scientific specialist groups of the World Conservation Union (IUCN), as well as with scientific advisors Regional taxon advisory groups tend to develop priorities that are complementary to those in other areas; for example, Europe may choose to allocate space to breed a different species of penguin than North America Taxon advisory group priorities are formalized into ‘‘regional collection plans,’’ which ideally include a justification for including or excluding each species or subspecies in the taxonomic group, as well as setting a target population size for each managed population These plans may also specify areas where research is needed, or where field conservation should