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Last Animals at the Zoo: How Mass Extinctions Can Be Stopped.

This book presents a spirited defense of modern zoos, based on the assertion that their most important function is the breeding of endangered animals. To this end, the author examines in detail the present plight of animal life on Earth, the theory and practice of ex situ conservation breeding, and new technologies for manipulating reproductive physiology to this end. The last two chapters deal with enriching zoo habitats for the benefit of animals and with the future of zoos.

Tudge argues that the loss of habitat on a grand scale is inevitable. In his view, zoos must function as long-term arks until political stability returns two centuries (or more) down the road and restoration becomes possible. "At present," he writes, "we are making life intolerable for wild animals, and in particular for large ones. This state of affairs is liable to persist at least for 500 to 1000 years, a time that |conservation biologist Michael~ Soule has called 'the demographic winter.' After that life could in theory become progressively easier." Much of the book is therefore devoted to proving that zoos can save many vertebrate species for that time.

Zoo opponents have objected that animals bred in zoos will not be genetically viable or behaviorally wild by the time they can be returned to nature. This book establishes beyond doubt that these objections are invalid. Critics have also presented ethical arguments against confining animals in zoos. These arguments can be overwhelmingly refuted, and some of the counterarguments are aired in this book. Tudge also addresses the problem of determining which creatures to include in the tiny fraction that we have the resources to save.

As a tropical biologist metamorphosed into a zoo director, I am devoted to all kinds of bioexbibits: zoos, aquariums, botanic gardens, and museums of anthropology and natural history. Therefore, I welcome and admire this book. Although I disagree fundamentally with Tudge's views on the function and future of zoos, he demonstrates successfully that zoos can play a crucial role in conserving one small group of animal species--the vertebrates.

Saving species

Tudge's treatment of the extent of animal diversity and the causes of its present reduction is full of good stuff, ammunition for both the conservationist and the zoo supporter. He explains yet again that, on land, the tropical rainforests are overwhelmingly the centers of biological richness. The rest, all other habitats combined, almost certainly contain fewer than 10 percent of animal species. This central fact cannot be stated too often.

Among the causes of species loss, Tudge lists hunting, introduction of new species, destruction of habitat, and the secondary effects of these activities. But this analysis is flawed: Because it examines species losses worldwide, it puts less emphasis on the one major factor at work in the tropics--habitat degradation or destruction resulting from human activity. The population explosion in the Third World, which is stimulating the extension of agriculture into the previously unexploited rainforests, is the root of the problem. Recognition of this fact has to precede solutions.

What are the solutions? Tudge vacillates between proposals to save species in zoos and iterations of the need to save habitats. He presents an elegant analysis of the enormous difficulties involved in maintaining reserves, particularly in tropical grasslands and savannas. The management of large mammals is especially difficult because of the need to provide for seasonal migrations, balance populations, and establish corridors for latitudinal migration in the event of global climate change.

Behind this analysis, however, is an unstated preoccupation with the habitats of the great game areas of East Africa. These are the sources of many popular zoo animals and also of the biological expertise of many zoo staff and directors. However, these areas are far less significant in floral and faunal diversity than the rainforests of the world. There, the overwhelming diversity is in the small animals. By deciding to focus on zoo breeding programs as the vehicle for species conservation, Tudge turns his back on the majority of tropical forest species.

Advances in health and husbandry

The section on breeding animals in zoos is a masterly short review of the skill and sheer genius that zoo nutritionists, veterinarians, ethologists, curators, and keepers have applied to enhance the health and husbandry of animals in their care. This is an area of great progress over the past 40 years and almost exponential recent progress. Tudge's treatment of breeding programs establishes the feasibility of creating zoo populations in which genetic and behavioral health can be maintained over the long term, albeit for a space- and resource-limited number of species. It also contains a lucid analysis of the criteria that can be used to determine which species we should save. The bottom line is a conclusion that I will return to later: "in the fullness of time, if they truly cooperated and committed themselves to captive breeding, zoos worldwide could probably maintain viable populations of all the 2,000 species of land vertebrates that are now thought to be seriously endangered."

Tudge starts his chapter on the theory of conservation breeding with an account of the theory of genetics, which introduces problems of inbreeding and maintaining genetic diversity. Many of these arise from the difficulties of managing small populations. It is here that theory has advanced greatly in recent years. There is now no doubt that inbreeding has deleterious effects. In fact, the primary evidence came from zoo studies (actually from studies by my own staff). Tudge would have done well to stress the fact that zoos are an important resource for all kinds of biological research--a fact that needs repeated emphasis in these days when zoos are under attack from the animal rights movement.

In general, however, Tudge's treatment here is thorough, the errors minor, and the exposition clear and readily understandable. In this respect, this book is ahead of the recent crop of books on the importance of modern zoos and their role as species-saving arks. My only criticism is perhaps a matter of personal taste: I don't think it is necessary, or even desirable, to go all the way back to Mendel's experiments with peas, detailed at great length, to explain the mechanics of inheritance.

The book then presents a series of case histories of zoo breeding programs. From the Arabian Oryx to the Golden Lion Tamarin, we have saved some masterpieces of evolution. This detailed record of triumphs of dedication and skill is splendidly told. It is something to dip into over and over when the effects of human greed and stupidity seem overwhelmingly disastrous.

Tudge links this discussion to an extensive and well-documented treatment of what its practitioners misleadingly call "artificial reproduction." The use of techniques such as artificial insemination, in vitro fertilization, embryo transplantation, and the cryopreservation of germ cells and embryos have allowed us to extend our species-saving efforts. They even promise to enable us to augment the genetic variability of wild populations, by implanting genetically enriched embryos in wild females, rather than introducing males or females to the wild population. (This is one of the few areas of science in which research based on humans is benefiting animals!)

Once the feasibility of breeding genetically healthy animals in zoos is established, the final problem is to ensure that they are behaviorally healthy. If zoos can provide animals with opportunities to engage in wild behaviors, these behaviors may be retained over a period of centuries, so that preserved species can ultimately be reintroduced into the wild. Moreover, if this is done, the moral argument against captivity loses much of its impact.

Fittingly, Tudge includes a whole chapter on habitat enrichment in zoos, explaining many of the advances that have been made in that area. At the moment, the successes of habitat enrichment are more likely to result from pragmatism than theory. As an ethologist I feel that we are only just skimming the surface of understanding the responses of wild animals to the components of their habitats. If there is one overriding conclusion to be drawn from classical ethology, it is that animals do not respond to all they are capable of perceiving. Our own intuitions about their responses are more frequently wrong than right. Zoos provide a valuable research resource for studying this vital area of behavior.

The zoo of the future

In general, then, this book is successful in showing that endangered animals can be sustained in existence in zoos. However, the book's subtitle is totally misleading. The mass extinctions that threaten life on Earth at the end of this century and the beginning of the next simply cannot be stopped by ex situ breeding programs in zoos and elsewhere. We are talking about much more than the loss of 2,000 land vertebrates. At the most, zoos can save only a tiny fraction, less than hundredths of one percent, of threatened species of animals, let alone plants. This is a fact that Tudge himself repeatedly acknowledges. The only way that mass extinctions can be stopped is by saving habitats.

Along with many other tropical biologists, I believe that zoos have a more important function than saving a handful of charismatic megavertebrates. They are, potentially if not often actually, a powerful vehicle for biological education. Here people can be moved by the wonder and glory of real living things to act to save ecosystems, rather than species. Species-saving is valuable for a handful of irreplaceable masterpieces, but we must save the gallery, not some of the paintings. Education, not breeding, must be the principal task.

The question with which the book opens--Why conserve animals?--reveals an outmoded view of zoos. It implicitly excludes the complementary half of the living world, inseparable from animal life: the world of plants. There is no point saving animals if the organisms on which they depend are gone forever.

Moreover, the role of zoos in conservation need not be limited by the idea that the public is interested only in lions, elephants, and giraffes, as the author implies. Millions of Americans are passionately interested in birds of all shapes, sizes, and colors. The rainforests are the winter feeding grounds of our migrant birds, and though there are no pandas there, the threatened destruction of these species' winter habitat may galvanize bird-lovers as much as did the publication of Rachel Carson's Silent Spring. People can also get excited about the extinction of fishes, reptiles, or insects. More tropical fishes are sold annually in the United States than there are people in Britain. Invertebrate houses are popular at zoos that have them. Butterfly exhibits have blossomed all over the United Kingdom. Many people have already passed beyond concern for the cute and cuddly. It is not just defeatist but unrealistic to suggest that conservation policies have to be based on the attractions of the relatively simple savanna faunas of East Africa.

Tudge is right when he contends that the future of life on earth depends on attitudes. I differ from Tudge in thinking that attitude changing, not captive breeding, should be a zoo's primary concern. By giving people in urban societies direct experience of living plants and animals and by providing a rational basis for appreciating the complexity of life, zoos can serve as a catalyst for creating attitudes of concern and respect for the living world.

The information revolution will change the face of zoos in the near future. Visitors will be able to stand next to a rainforest exhibit and use hand-held CD-ROM players to investigate its myriad complexities and connections to a great range of subjects. Looking at the facial markings of a cheetah, they can access movies of Kabuki actors making up their faces with similar markings or football players dabbing shadow lines under their eyes. Virtual reality programs promise to allow zoo visitors to experience forms of animal behavior, such as predation or mating, that cannot be easily observed in zoos. These emerging technologies will both enhance and integrate our understanding of our place in the living world.

At the same time, an even more profound change of character is needed in our bioexhibits. In a world that is increasingly emphasizing interconnections in every branch of knowledge, the Victorian fragmentation of bioexhibits into zoos, botanical gardens, aquariums, natural history museums, and even art exhibits must be ended. If we are really to inspire concern for all of life, in its wondrous interconnectedness, zoological parks should evolve into holistic biological parks. By reuniting the sundered sphere of life and proclaiming every aspect of its glory, these bioexhibits could instill in us a biological literacy that is as important to our enlightenment as were the classics and theology in medieval times.

Michael H. Robinson is the director of the National Zoological Park in Washington, D.C.
COPYRIGHT 1993 National Academy of Sciences
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Author:Robinson, Michael H.
Publication:Issues in Science and Technology
Article Type:Book Review
Date:Mar 22, 1993
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