Biology of Gila Monsters and Beaded Lizards . 2005 . The University of California Press , Berkeley , California . 247 pp . $49.95 (hardcover) . ISBN 0-520-24357-9 .
Considering the vast array of species on this planet, only a small fraction get a well-written comprehensive book dedicated to them. The Gila monster and beaded lizards, however, receive an encore presentation. Bogert and Martín del Campo (1956) set the bar high with their impressive tribute to helodermatid taxonomy, anatomy, ecology, and human dimensions. Nevertheless, complete works become incomplete over time and new discoveries revise our understanding of species. Thus, Dan Beck took on the challenge of rediscovering the Gila monster and beaded lizard.
The Gila monster, Heloderma suspectum, and the beaded lizard, H. horridum, are the lone extant representatives of a genus deserving of attention. These lizards are the biggest in North America and are the only venomous lizards in the world. History of the American Southwest is dotted with legends about these animals, especially fantastic exaggerations regarding their venom. Early scientific efforts dispelled the folklore, but made bold conclusions based on limited data, resulting in a dogma of questionable accuracy. Nevertheless, the last 20 years have produced a vast array of data-based studies that are shedding light on the truth.
Biology of the Gila Monsters and Beaded lizards opens with a forward by Harry Greene of Cornell University. The choice of Greene is especially appropriate because Beck clearly has been influenced by Greene's (2000)Snakes: The Evolution of Mystery in Nature. As Greene does in his work, Beck carefully addresses the biology of these unique lizards with a thorough presentation of what is scientifically known about them and then combines it with a human touch of quotes and anecdotal stories that personalize the book, giving the animals (and the author) a tangible reality, especially to those who have not had the pleasure of encountering one of these animals in the wild.
Beck does a masterful job in basing the book on data that have been collected, not speculation and anecdotal information. Although the text is not free of speculation, it is clear when the author is presenting conclusions based on data verses those based more on his suspicion. Although an author of such a book has the opportunity to selectively “review” the literature, the data presented are complete and the author does not bias his conclusions based on his personal findings compared with those of others. I am included in that list of others who have worked with these amazing creatures. When I first presented some of my results to Professor Beck, he responded by stating that my results do not agree with what he has seen with his geographically distinct populations. He followed by stating he looked forward to my expansion, and in some ways revision, of what we “know” about helodermatids. This open-mindedness is clear throughout the text.
The first chapter provides the human dimension of helodermatids in an overview of the origin of the names (Latin, English, and, appropriately because of their distribution, Spanish), folklore, and the “evolution” of scientific study of helodermatids. Such a chapter is usually saved for the tail end of such a book, but it fits appropriately at the front because this organization effectively demonstrates the “evolution” of the human–helodermatid relationship. In addition, this opening chapter recognizes the efforts of numerous scientists and the value of the collective product.
Chapter 2 addresses the evolution and distribution of helodermatids, covering both the extant and fossil records. The high-quality tables, figures, and plates make this section a strength. Relatively unique and especially valuable are the plates that provide not simply a single representative of each taxon, but collages of photos for numerous populations that effectively demonstrate the variation (and similarities) within populations.
The next chapter is a thorough, but seemingly misplaced discussion of helodermatid venom and envenomation. The discussion of the venom delivery apparatus is one of only a few places in the book where anatomy is discussed. Although additional information regarding helodermatid anatomy would be valuable, this limitation is more a result of a limited database than the author's failure to compile the existing literature.
The ensuing chapters are the strength of the book and the justification for the need to follow-up on Bogert and Martín del Campo (1956). These chapters compile recent literature on the ecology, physiology, and behavior of helodermatids. The greatest amount of data exist for the thermobiology of the species, and the author reviews the literature effectively, including numerous graphs from a variety of studies by the author and others. A common thread among the studies is that helodermatids do not tightly control their body temperature and are active at a wide range of temperatures. They avoid activity when it is hot, and thus, although they live in what is considered an extremely hot environment, their activity patterns lead to relatively low active body temperatures compared with that of most lizards.
Energetically, helodermatids also seem paradoxical. They employ an active foraging strategy to locate vertebrate nests, yet use 10% or less of their maintenance budget on activity. Nevertheless, these estimates are a result of very low activity levels of particular populations, and the author acknowledges that data from other investigators studying different populations suggest much greater activity and likely much higher energy budgets for activity.
The author uses a similar comprehensive and graphic presentation to describe habitat use, activity patterns, feeding ecology, and reproduction. The book concludes with discussions on conservation issues and future directions. Overall, the author effectively presents the current state of knowledge regarding Gila monsters and beaded lizards. The amount of data that have been collected on these species in the last two decades is impressive and well deserving of compilation. The result of Beck's work is a well-written, well-organized, and complete text that makes a major step in the maturation of helodermatid information from folklore to speculative anecdotes to data-based conclusions. Although many questions remain unanswered, thanks to Beck (as both an author and a field biologist), there now exists an updated comprehensive resource on the biology of helodermatid lizards—unique and scientifically fascinating creatures.