A Timelessly Valuable Survey

Authors

  • Harry W. Greene

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      I have no financial, editorial, or advisory relationships with Cornell University Press, other than as an occasional outside reviewer of book proposals and manuscripts.


Cusco Amazónico: the Lives of Amphibians and Reptiles in an Amazonian Rainforest . Duellman, W.E. 2005 . Cornell University Press , Ithaca , NY . 448 pp . ( 433 + xv ). $74.95 (hardcover) . ISBN 0-8014-3997-3 .

This book is about the nitty-gritty details of a biologically rich place, and as such it epitomizes exploratory natural history, an endeavor whose challenges and central role in conservation are not always widely appreciated. Cusco Amazónico is a privately owned ecotourism lodge on a 10,000- ha preserve, adjacent to the Rio Madre de Dios in the lowlands of southeastern Peru. Duellman masterfully summarizes studies of its 151 species of frogs, caimans, turtles, lizards, amphibians, and snakes (with salamanders and caecilians, not yet recorded from the site, these animals are informally and collectively called “herps”). His stated goals were to (1) describe the physical environment and vegetation at a seasonal rainforest site in the southwestern Amazon Basin, (2) offer a thorough analysis of ecology of herps at that site, (3) provide identification keys in English and Spanish for all herps known from the Departamento de Madre de Dios, Peru, and (4) present detailed natural histories for all herps known from Cusco Amazónico. Below I justify my view that the second objective is worthwhile but unrealistic, but Duellman succeeds admirably in fulfilling the other goals. This is without doubt a milestone publication in tropical vertebrate biology.

Cusco Amazónico's 16 chapters are arranged in five parts and are followed by an epilogue, glossary, literature cited, and two indices. In addition to numerous graphs, line drawings, and maps, there are 12 color illustrations of habitats and 224 more of live herps. The photographs vary in quality from mediocre to excellent, but they all facilitate species identifications and provide readers with a feel for the tremendous diversity encompassed by this Neotropical herpetofauna. On a more subliminal level, from an emerald leaf-frog (Agalychnis craspedopus) that resembles lichen-encrusted, herbivore-damaged foliage to a 2.6-m-long bushmaster (Lachesis muta) “in cruising mode,” the color images evoke some of the reasons why field biologists pay especially careful attention to their surroundings.

Part 1 (“Beginnings”) encompasses an introduction and methodology. This book is based on 1081 person-days of fieldwork and 9484 observations of different individual animals, of which 4071 were collected as museum specimens. Duellman himself made eight trips to the site for a total of 223 days, and dozens of individuals from seven countries also contributed to the fieldwork. Data for the specimens are electronically accessible and linked to archived field notebooks, which also include observations on individual animals that were not collected. All the information underlying this book is thus available for independent assessment and further synthesis (W. E. Duellman, personal communication; consult http://www.nhm.ku.edu/herpetology).

Two chapters in part 2 (“The Environment”) describe in considerable detail the “Physical Environment” (location, topography, hydrology, soils, climate) and “Vegetation” (structure and composition, quantitative comparisons of floristic diversity, comparisons with other areas) at Cusco Amazónico. The latter chapter was made possible by access to electronic data bases at the Missouri Botanical Garden.

Part 3 (“Life in the Rainforest”) includes seven chapters. “The Herpetological Assemblage” briefly summarizes taxonomic composition of the fauna and discusses species discovery rates. “Abundance and Mass” provides summaries and raw data for these topics, which are rarely available in faunal surveys and will thus prove especially valuable for future applications. A chapter on “Seasonal Patterns” evaluates activity relative to annual variation in temperature, rainfall, lunar phases, and food resources. “Living in the Environment” considers ecological differences among species in activity, habitat, feeding biology, and mass. Not much was learned about certain elusive taxa, but sufficient quantitative data were obtained for many others (e.g., 45 prey types found in 181 specimens of 22 species of lizards) to delineate numerous interesting relationships. “New Generations” examines the herpetofauna with respect to breeding season, reproductive modes, and other life-history aspects. “Biogeography” summarizes Amazon Basin geology, analyzes regional similarities and differences among Amazonian herpetofaunas, and places the amphibians and reptiles of Madre de Dios in deep historical perspective. “ Human Impact” discusses habitat degradation, protected areas, protected species, ecotourism, and collecting.

The overall goal of part 3 is unrealistic because accumulating and then “thoroughly” exploring the ecological implications of such a large and diverse data set is probably beyond the abilities of any one biologist. Here Duellman explores a number of local patterns with little attempt at broader generalizations, although there are provocative, mostly site-specific, discussions of interactions between frogs and lizards, comparative spatial distributions, herpetological diversity in relation to plant diversity, and historical ecology. His findings thus provide abundant opportunities for comparisons with other assemblages, herpetological and otherwise. It probably will not be long before someone throws caution to the wind and examines the Cusco Amazónico herpetofauna in the light of Hubbell's (2001) neutral theory of biodiversity. At first glance, Figs. 6.1–6.6 look like “Hubbell-o-grams” (they are not) and Tables 6.2–6.4 provide the relevant raw data, although of course accurately estimating population densities for herps is far more problematic than mapping the trees on which they live.

The empirical core of this book, about 55% of its pages, is in parts 4 (“The Amphibians”) and 5 (“The Reptiles”). In these chapters Duellman provides bilingual keys to the major groups and to individual species and detailed accounts for the latter. There is a separate chapter on tadpoles in part 4. Each species account includes, insofar as relevant, information on original description and type locality, identification, characteristics, occurrence, reproduction, acoustic behavior, tadpoles, and food. Each account closes with a remarks section, which includes the few observations on antipredator mechanisms—a topic that is surprisingly underrepresented here, given that earlier tropical naturalists often focused on interspecific interactions (e.g., Alfred Russel Wallace [1867] discovered coralsnake mimicry). I also wish Duellman had more frequently underscored taxon-specific vulnerability, about which field biologists are uniquely prepared to comment. The stunningly beautiful Agalychnis craspedopus, for example, breeds in small pools on the upper surfaces of tree buttresses and fallen logs, an unusual behavior with conservation implications for certain forestry practices.

Parts 4 and 5 are at once a compendium of most of what is known about the 151 species and, especially in the context of the preliminary insights provided in part 3, an endless smorgasbord of questions for new research. Given the tantalizing reproductive and metamorphic diversity of tropical amphibians, might they encompass useful new models for addressing problems in evolutionary developmental biology? How do design rules for crypsis in snakes change across such extensive variation in body mass (from ∼1 g in some blindsnakes to >10 kg in anacondas)? What are the community-level implications of terrestrial predation by dwarf caimans (Paleosuchus trigonatus)? What are the ecological correlates of apparent rarity in this herpetofauna, and how might they relate to extinction risks? I can imagine challenging new graduate students, regardless of their taxonomic and conceptual interests, to formulate a dozen dissertation topics based solely on reading the species accounts and perusing the illustrations in Cusco Amazónico.

While I was drafting this review an ornithologist asked me to identify a snake he had photographed in the Chocó region of Ecuador. His image shows a large colubrid that clearly pertains to a widespread group of ecologically important serpents, but evidently no known Chironius is immaculate black dorsally and ventrally (Dixon et al. 1993). In the good old days he would have collected that animal, deposited the specimen in a museum, and a herpetologist could have assessed its scalation and other diagnostic attributes. Now only a taxonomically dedicated individual would endure the layers of bureaucracy required to have legally killed and preserved that snake, even for curation in the country of origin. If it had been collected, though, I could glean behavioral observations from field notes and examine its stomach contents, someone could evaluate its reproductive condition, and others might use a tissue sample to evaluate its genetic relationships. Future questions posed with the specimen in hand would have been limited only by our imaginations, and the resulting data—the species-focused natural history that inevitably forms the core of biology (Greene 2005)—could have informed conservation priorities and the field guides that inspire nature appreciation.

I offer that anecdote because I believe, with no condescension intended, that many biologists are unaware of the increasing frequency with which species go extinct even as formal descriptions await publication (e.g., Wake & Campbell 2001). If a spectacular new Chironius does indeed live in northwestern Ecuador, the likelihood of its discovery is rapidly diminishing in the face of environmental change. Writ larger, our ignorance of the real breadth of biodiversity is stunning. The consequences for conservation are likewise sobering: no publication comparable to Cusco Amazónico as yet exists for the Chocó, or indeed for most groups of organisms at any other rainforest sites worldwide (e.g., for an overview of Brazilian reptiles, see Rodrigues [2005]). Duellman closes this monograph with a futuristic parable about fieldwork in an age of portable DNA sequencers and satellite-accessible data bases, as three young researchers resample the site and find even greater herp diversity than was documented in the late twentieth century. Let us hope his own timely and valuable survey is a harbinger of more widespread support for such studies rather than the requiem for a lost biota. I urge those who can afford extra copies of Cusco Amazónico to take them to Latin America for students and libraries.

Footnotes

  • *

    I have no financial, editorial, or advisory relationships with Cornell University Press, other than as an occasional outside reviewer of book proposals and manuscripts.

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