Book Reviews

Tortoises of the World. Giants to Dwarfs

G. R. Zug and D. A. Reese. 2024. Johns Hopkins University Press. ISBN 9781421448350. 228 p. $49.95 (hardcover).—

Everybody likes turtles. And everybody loves tortoises. Add to that the fact that turtles and tortoises (Testudines) are among the most threatened major clades of vertebrates on Earth, and that Testudinidae (tortoises) has the highest proportion of its species threatened or endangered (Turtle Taxonomy Working Group, 2025), and it’s clear that a volume dedicated to the biology of the tortoises is certainly timely. George Zug, one of the leading herpetologists of our time, and Devin Reese, an equally accomplished science writer and natural historian, have teamed up to produce a volume that should appeal to anyone with a more than casual interest in the group.

The book follows a relatively tried and true formula for taxon-focused monographs, with the first six chapters dedicated to the basic body plan, physiology, reproductive behavior, and ecology of the world’s approximately 47 extant and eight recently extinct species of tortoises. This is followed by a longish Chapter 7, organized by major geographic regions of the world, which contains a paragraph on nearly every species (except a few recently extinct Mascarene Islands giants, which are treated as a group). The last part of the book includes chapters covering tortoise evolution, human interactions, and conservation.

Among the first six chapters, much of the information on basic body plans (Chapter 2), physiology and behavior (Chapter 3), and to a lesser extent reproduction (Chapter 4) is a review of Testudines, and sometimes all reptiles, rather than tortoises specifically. While there is nothing wrong with the information presented, it can lead to confusion when attempting to distinguish between the authors’ description of a more inclusive group (e.g., all turtles), vs. characters or features that are unique to tortoises. There were some minor annoyances that I noted: “Natural selection for characteristics related to reproduction has led to sexual dimorphism in tortoises” (p. 58) should, in my view, attribute such variation to sexual rather than natural selection. The data on carapace shapes (Table 2.1), egg size and shape (Table 4.1), and clutch size as a function of carapace length (Table 4.2) are interesting, but why not provide that information for all species for which it is available rather than just a few? On the plus side, all of these chapters are sprinkled with fascinating facts—Common Ravens account for 70–91% of the mortality of young Mojave Desert Tortoises (Gopherus agassizii); female sexual maturity is reached at 70% of adult body size in all turtles (something I did not know); tortoises are ecological “keystone species” given their propensity to burrow, make wallows, and modify vegetation; Spur-thighed Tortoises (Testudo graeca) are picky herbivores that only ate a quarter of the plants available to them in a field study in Algeria. I was intrigued by the description of a study that found that excluding Mojave Desert Tortoises led to an increase in rare plant diversity, but was somewhat confused when, in the same section, we were told that “By reducing the density of their preferred plant species, foraging by tortoises allows other plants species to gain a foothold” (p. 103). Perhaps both are correct, but a little more detail would help explain this seemingly paradoxical finding.

For me, the book really hit its stride in the final three chapters. Chapter 8, Ancestry and Evolution, provides a succinct, broadly accessible account of the early evolution of turtles. The literature on early stem Testudines is complicated and often inaccessible to non-specialists, and the authors do a great job of introducing the key players in early turtle evolution. However, I doubt they really meant it when they said tortoises “arose from a lineage of geoemydid turtles” (p. 145), implying that Geoemydidae is paraphyletic with respect to Testudinidae, while providing no evidence for this novel hypothesis (the two lineages have been recognized as reciprocally monophyletic sister taxa in all recent studies; Thomson et al., 2021). I really appreciated the continent-by-continent account of the fossil history of tortoises through time, emphasizing the unique nature of each continent-level radiation over the last 65 million years.

Chapters 9, Tortoise Decimation by Humans, covers current threats ranging from disease and roads to the seemingly insatiable pet trade, as well as traditional medicine and climate change. Their summary is simultaneously fascinating and disturbing. They report that in 2016, the US was the top importer of turtles (presumably including tortoises) in the world, with China and Hong Kong close behind. Shame on all of us! While this section of the book paints a bleak outlook for the future of tortoises, Chapter 10 on Tortoise Conservation highlights successes. These include laws (e.g., Endangered Species Act of the USA), international agreements like the Convention on International Trade of Endangered Species of Wild Fauna and Flora (CITES), and various acts aimed at preserving biodiversity, including tortoises, in Africa, Southeast Asia, and China. The section on conservation actions provides detailed information on 11 tortoise species that is well researched, positive in its outlook, and provides workable models for many other species that suffer from overexploitation and habitat loss. This was a wonderful, optimistic way to end the book.

I have three gripes that warrant consideration. First, there is not a single phylogeny in the volume—not one depicting the placement of turtles within amniotes, or tortoises within Testudines, or how ancient stem species are related to crown Testudines. That information is well established in the recent scientific literature, including the general papers that they cite in the “Further Readings” at the end of the volume, and a tree or two would have been a welcome, clarifying addition to the text descriptions. Second, and more importantly, there are no in-text citations to the literature. The authors tell us that their goal is to “avoid the disruption that occurs with in-text citations” (p. ix); therefore, they prefer to leave the text non-annotated and provide a downloadable list of references for each section. While this may be suitable for some readers, I found myself constantly wanting to learn more about some nugget of information, and this format made it very difficult to find the relevant sources. Third, when I opened the book, the first ten pages fell out of the binding. I hope this defect was unique to my copy, but the publisher should check with their binder about quality control.

These gripes aside, I thought this was a great volume. In many ways, it reminded me of George Gaylord Simpson’s (1976) classic volume on penguins (Penguins: Past and Present, Here and There). Like Simpson’s monograph, this is an informative, expert-driven book on an iconic group of organisms that deserves our attention. Buy it and read it. You’ll learn a lot about tortoise biology and conservation.

H. Bradley Shaffer, Department of Ecology and Evolutionary Biology, and La Kretz Center for California Conservation Science, University of California Los Angeles, Los Angeles, California 90095; Email: brad.shaffer@ucla.edu.

California Amphibians and Reptiles

Robert W. Hansen and Jackson D. Shedd. 2025. Princeton University Press. ISBN 9780691249070. 520 p. $35.00 (paperback).—

It is rare to find a book that is a challenge to review because it merits such high praise across the board. This long-awaited field guide to California’s amphibians and reptiles in The Princeton Field Guide series sets a new standard for the genre—it is thorough, accurate, innovatively and beautifully produced, and user friendly at all levels of interest and expertise. In fact, the more you know about the California herpetofauna, the better you will appreciate it.

Hansen and Shedd have made an impressive effort to assemble the components of this guide. The information content is exceptional, some of it appearing here for the first time. They have truly mined all the expertise available—over 300 individuals are credited with assisting in various ways, and more than 60 taxonomic and regional experts contributed to the currency and accuracy of the range maps. Virtually all the photographs, paintings, and figures are new. Utility extends even to the color scheme of the maps, chosen to facilitate accessibility by those with color-vision deficiency.

The volume follows a fairly standard format for regional guides, with 20 pages of useful introductory material (including a concise illustrated review of the diverse biotic communities in the state), 200 pages of species accounts (including established exotics and potential residents), 164 pages of high-quality photos and 30 pages of excellent renderings of amphibian larvae, 61 pages of range maps, a section on the rationale for taxonomic decisions (with more than 90 citations, two-thirds from the last 15 years), a glossary, sections on resources and snakebite, and finally an index by both common and scientific names listing accounts, illustrations, and range maps for each.

The species accounts are concise and accurate, mostly 1–1.5 pages each, with a lot of useful natural history information included. The identification sections are unusually thorough, often describing ontogenetic, sexual, and geographic variation in appearance and size, and are frank about the difficulties in identifying some species, such as many of the slender salamanders (Batrachoseps spp.) without (or even with) precise locality information. The sections on distinguishing similar species are often quite detailed and complemented with detailed information on the areas where confusion is likely to occur. Every aspect of these accounts reflects a high level of familiarity that is rare in any work of this scope.

The most innovative aspect of the book is the color plates, which are either photographs (both authors) or expertly executed paintings of larvae by Shedd. All photo subjects face right, and all larvae face left. Every photo is sharp and nicely printed, but what makes this guide unique is that several individuals are depicted, with the county of origin for each noted. The species plates illustrate both ontogenetic and geographic variation. It is hard not to be impressed by three full pages (17 animals) of color and pattern variation in Gilbert’s Skinks (Plestiodon gilberti) or 14 geographic and ontogenetic variants of Banded Geckos (Coleonyx variegatus). Most herpetologists have never seen a Tehachapi Slender Salamander (Batrachoseps stebbinsi) or an Inyo Mountains Salamander (B. campi), let alone six photos of the major differences in color and patterning for each species. Two as-yet undescribed species of Batrachoseps and two new Hydromantes salamanders are also well illustrated. The plates feature ten Mountain Kingsnakes (Lampropeltis zonata), 14 California Kingsnakes (L. californiae), and 11 Gopher Snakes (Pituophis catenifer ssp.). You get the idea—anyone can learn about geographic color and pattern variation from these illustrations.

In my view, the most impressive feature of the book comes from a close examination of the distribution maps (although I wish many were produced in larger format). Of the 122 maps, 65 depict the ranges of single species, 35 show two, 11 show three, nine show four, and one each depict ranges of five and seven species. The information content of the maps alone is worth owning the book. Critically, many maps show where each species is not known to occur with accuracy down to the limits of the printing. Like many of my colleagues, I reviewed draft maps for areas where I had decades of experience. I detected only two small errors that made it through to publication: California Newts (Taricha torosa) are present in the Salsipuedes Creek drainage north of the Santa Ynez Mountains in western Santa Barabara County; and Western Spadefoots (Spea hammondii) do not occur on the coastal slope of the Santa Ynez range in western Santa Barbara County.

If there is one thing I wish had been done differently, it is to scrap the evident goal (likely of a design consultant) to maintain most of the maps as full state figures. Much smaller areas are shown in 14 cases, but a north–south division of the state, either at San Francisco (nine maps) or Monterey bays (36 maps), would have allowed those maps to be printed at 30–50% larger sizes, with a concomitant increase in utility. These maps are perhaps the most important information in an already uniquely valuable contribution to western North American herpetology, so they deserve to be more accessible without pulling out your reading glasses. Older users may want to paste an envelope on the inside rear cover for a magnifying glass.

The suggested format for Ichthyology & Herpetology book reviews includes several categories (deliverables, rank, accuracy, writing, value, and market), all of which I would rate as outstanding. This book is so far superior to anything else for the region that it will likely go unsurpassed for a long time (although the authors are now working on a guide to the entire western USA). The book is priced fairly and will take a beating in use. I recommend it to anyone anywhere as an example of what is possible when authors seek to set a new standard of field guide excellence.

Samuel S. Sweet, Department of Ecology, Evolution, and Marine Biology, University of California, Santa Barbara, California 93106-2014; Email: goannafan@ucsb.edu.