Iguanas: Biology and Conservation

Allison C. Alberts
Ronald L. Carter
William K. Hayes
Emília P. Martins
Copyright Date: 2004
Edition: 1
Pages: 372
  • Cite this Item
  • Book Info
    Book Description:

    In what is certain to be the key reference on iguanas for years to come, some of the world's leading experts offer a clear and accessible account of the latest research on the evolution, behavioral ecology, and conservation of these highly visible and increasingly endangered creatures, much loved by professional herpetologists and hobbyists alike. The book begins with an introduction by noted iguana biologist Dr. Gordon Burghardt that examines the state of iguana research—past, present, and future—with an emphasis on social behavior. Three major sections follow, each opening with a synthesis by the volume editors, who survey the current status and likely future direction of investigations in the pertinent area. The first section focuses on different aspects of the taxonomic and morphological diversity of iguanas and includes a complete checklist of species. In the second section, contributors address the behavior and ecology of iguanas and provide compelling evidence that both may be far more complex than previously appreciated. The third and final section, highlighting the threats facing iguana populations today, describes the broad array of innovative conservation strategies that will be needed to help ensure their survival. Illustrated throughout with photographs, distribution maps, tables, and figures, this volume will be the definitive resource for anyone—professional or curious amateur—interested in iguanas.

    eISBN: 978-0-520-93011-7
    Subjects: Biological Sciences

Table of Contents

  1. Front Matter
    (pp. i-iv)
  2. Table of Contents
    (pp. v-vi)
  3. List of Figures
    (pp. vii-x)
  4. List of Tables
    (pp. xi-xiv)
    (pp. xv-xvi)
    (pp. 1-12)
    Gordon M. Burghardt

    The 1997 symposium in Seattle on which the present volume is based was held exactly fifteen years after the publication ofIguanas of the World: Their Behavior, Ecology, and Conservation,which A. Stanley Rand and I edited (Burghardt and Rand, 1982). It was based on a symposium we organized that took place in 1979 at the combined Society for the Study of Amphibians and Reptiles/Herpetologists League (SSAR/HL) meetings in Knoxville, Tennessee. Of the people attending and presenting at that conference, I am the only one who also presented in Seattle. Most of the other attendees have moved on to other...

  7. Part I Diversity
    • Introduction
      (pp. 15-18)
      Ronald L. Carter and William K. Hayes

      The study of diversity and adaptive relationships between structure and function are traditional themes in biology that have been rejuvenated recently by developments in molecular biology, morphometric analysis, and bioinformatics. Using methods of comparative biology, the study of unique and shared features proves to be heuristic and provides predictive tools in evolutionary biology. Understanding diversity at its various levels is a major challenge because we must identify it, measure it, catalog it, and name it, if taxonomically relevant. We must also seek to understand its underlying causes, limitations, and evolutionary history.

      Diversity is a dominant feature of life, whose extent...

      (pp. 19-44)
      Bradford D. Hollingsworth

      In this chapter, I provide an overview of the evolutionary diversity of iguanas to help synthesize the large volume of currently available knowledge and review the controversies that still exist. The family Iguanidae, as constituted by Frost and Etheridge (1989), was first formed as an informal taxonomic group of iguanian lizards referred to as “iguanines” (Savage, 1958; Etheridge, 1964). The current constitution of the family is based on the work of Etheridge (1964), who diagnosed the group by their unique caudal vertebrae. Since this early work, “iguanines” have been shown to be a natural group through characteristics of their skeletal...

    • 3 Genetic Contributions to Caribbean Iguana Conservation
      (pp. 45-57)
      Catherine L. Malone and Scott K. Davis

      Iguanas of the genusCycluraoccur only on islands in the West Indies. Throughout its distribution, this genus exhibits a high degree of endemism, with a single species or subspecies restricted to individual or small groups of islands (figure 3.1). Traditionally, species and subspecies have been described on the basis of morphology, and in many cases, a limited number of specimens were examined to establish taxa. Currently, there are eight described species and thirteen extant subspecies (Schwartz and Carey, 1977). Populations ofCycluraare being directly impacted throughout their ranges as a result of predation by both humans and feral...

    • 4 Genetic Structure of the Turks and Caicos Rock Iguana and Its Implications for Species Conservation
      (pp. 58-70)
      Mark E. Welch, Glenn P. Gerber and Scott K. Davis

      Many species of iguanas are composed of multiple isolated populations inhabiting islands or patchily distributed habitat (Burghardt and Rand, 1982). Species with this type of distribution often have genetic structures that reflect geographic relationships among populations (Avise, 2000). Broadly speaking, these structures may provide an indication of the degree of evolutionary independence among populations, and when combined with geohistorical information, the relative effects of vicariance and dispersal may be inferred.

      High rates of migration among isolated populations may serve to maintain genetic homogeneity across a species range. When isolation is complete, populations may diverge without restriction. If migration among populations...

    • 5 Tracing the Evolution of the Galápagos Iguanas: A MOLECULAR APPROACH
      (pp. 71-83)
      Kornelia Rassmann, Melanie Markmann, Fritz Trillmich and Diethard Tautz

      Molecular evolution is the process of molecular change in a lineage or taxon group over time. It comprises the modification of particular protein and DNA molecules in these lineages, as well as changes in their genome or the structure of their gene pools. Molecular evolutionary studies attempt, on the one hand, to characterize the processes and mechanisms that lead to molecular change. On the other hand, the knowledge gained from such work provides the background for the second area of interest in molecular evolution, the reconstruction of the evolutionary and natural history of organisms from molecular data. This chapter falls...

    • 6 Sodium and Potassium Secretion by Iguana Salt Glands: ACCLIMATION OR ADAPTATION?
      (pp. 84-94)
      Lisa C. Hazard

      The marine iguana(Amblyrhynchus cristatus)is well known for its unusual diet and foraging mode. Feeding on subtidal/intertidal algae, it incurs a high load of salts (primarily sodium chloride, with some potassium) from its food (Dunson, 1969; Shoemaker and Nagy, 1984). To cope with this high-salt diet, the marine iguana uses large cranial salt glands that excrete most of the sodium, potassium, and chloride ingested; forceful expulsion of the secreted fluid is the cause of the dramatic snorting and sneezing observed in these animals (Schmidt-Nielsen and Fange, 1958). Other lizards also possess these extrarenal osmoregulatory organs (reviews in Peaker and...

  8. Part II Behavior and Ecology
    • Introduction
      (pp. 97-100)
      Emília P. Martins

      Iguanas have long fascinated behavioral ecologists because they offer an exception to almost every generalization. The implicit hope is that by explaining the exceptions, we might also be able to understand the rule. Whereas most lizards are insectivorous, iguanas feed mostly on plants. Whereas most lizards are territorial, iguanas often live together in groups. Much of lizard behavior and ecology can be explained by understanding the phylogenetic history of the groups. For example, most lizards are probably territorial simply because their ancestors were territorial and there has not been sufficient selective pressure to change that behavior. In contrast, iguanas are...

    • 7 Behavior and Ecology of Rock Iguanas, I: EVIDENCE FOR AN APPEASEMENT DISPLAY
      (pp. 101-108)
      Emília P. Martins and Kathryn E. Lacy

      Most lizard species are either territorial or solitary, with social interactions being primarily aggressive (Martins, 1994). Iguanas are unusual in that several species congregate in groups (e.g., marine iguanas: Boersma, 1982; green iguanas: Rodda, 1992). Although these groups are sometimes temporary aggregations in areas where resources are abundant, iguanas can recognize and behave differently toward individuals of different dominance rank (e.g., Alberts et al., 1994) and may thus also be able to form social groups in which individuals recognize and behave differently toward members of their own group. A social lifestyle imposes special requirements on a communication system, including the...

    • 8 Behavior and Ecology of Rock Iguanas, II: POPULATION DIFFERENCES
      (pp. 109-118)
      Ahrash N. Bissell and Emília P. Martins

      Population differences in morphology and behavior may reflect evolutionary changes that can ultimately lead to further divergence and speciation (Mayr, 1970). Although differences in morphology, behavior, and genetics have been found within several lizard species, these differences are usually far less than the differences found among species (e.g., Wiens, 1997; Martins et al., 1998). Recent studies, however, have shown that genetic (Welch, 1997; Welch et al., this volume) and behavioral (Martins and Lamont, 1998) differences among populations ofCycluraiguanas can be substantial. In this chapter, we present new and more thorough data on population differences inC. carinatabehavior,...

    • 9 Sexually Dimorphic Antipredator Behavior in Juvenile Green Iguanas: KIN SELECTION IN THE FORM OF FRATERNAL CARE?
      (pp. 119-126)
      Jesús A. Rivas and Luis E. Levín

      The benefits of sociality have been widely discussed. Because the probability of detecting an approaching predator increases with the number of guarding eyes, it has been proposed that animals gain protection against predators by living in groups (Brown and Brown, 1987; Da Silva and Therhune, 1988; Yáber and Herrera, 1994). Other benefits to sociality include decreased likelihood of predation through the selfish-herd effect (Hamilton, 1971), active deterrence of predators (Gross and MacMillan, 1981), and confusion of predators through a perceptual bottleneck that leads to lower capture efficiencies (Krakauer, 1995).

      Studies of antipredator behavior in gregarious reptiles have not been thorough...

    • 10 Determinants of Lek Mating Success in Male Galápagos Marine Iguanas: BEHAVIOR, BODY SIZE, CONDITION, ORNAMENTATION, ECTOPARASITE LOAD, AND FEMALE CHOICE
      (pp. 127-147)
      William K. Hayes, Ronald L. Carter, Martin Wikelski and Jeffrey A. Sonnentag

      Marine iguanas(Amblyrhynchus cristatus)live in large aggregations along the rocky coastlines of the Galápagos Islands. They are unique among reptiles in that they forage almost exclusively on macrophytic algae in the intertidal and subtidal zones (Trillmich and Trillmich, 1986; Wikelski et al., 1993; Wikelski and Hau, 1995). They exhibit a lek mating system in which males cluster during the mating season and defend small, symbolic territories devoid of material resources other than sperm (Wikelski et al., 1996, 2001). These leks (clusters of territorial males) occur in the supratidal zone of the rocky coastline, where females also aggregate, presumably to...

    • 11 Environmental Scaling of Body Size in Island Populations of Galápagos Marine Iguanas
      (pp. 148-157)
      Martin Wikelski and Chris Carbone

      If we want to understand the striking patterns in body sizes seen in populations and communities of animals, we need to understand the key factors that influence body size (Blackburn et al., 1993; Brown et al., 1993; Melton, 1993; Cates and Gittleman, 1997; Kozlowski and Weiner, 1997; West et al., 1997; Perrin, 1998; Carbone et al., 1999). This is a challenging task, however, because size is linked to many other traits and is subject to a wide variety of selection pressures (Cluttonbrock and Harvey, 1983; Schmidt-Nielsen, 1984). Several approaches have been proposed to quantify body sizes within and across species....

    • 12 Environmental Influences on Body Size of Two Species of Herbivorous Desert Lizards
      (pp. 158-175)
      Christopher R. Tracy

      The implications of body size for the ecology and life history of animals have deservedly seen a great deal of study (e.g., Peters, 1983; Schmidt-Nielsen, 1984; Calder, 1996). Body size influences nearly every aspect of the functioning of an organism and is arguably the most important factor influencing the life history strategy of many organisms (Miles and Dunham, 1992). Recent comparative studies have shown that phylogeny explains much of the interspecific variation in body size of lizards (Dunham and Miles, 1985; Dunham et al., 1988; Miles and Dunham, 1992; Promislow et al., 1992; Petren and Case, 1997). However, local adaptation...

    • 13 Factors Affecting Long-Term Growth of the Allen Cays Rock Iguana in the Bahamas
      (pp. 176-192)
      John B. Iverson, Geoffrey R. Smith and Lynne Pieper

      The large, herbivorous rock iguanas of the genusCycluraoccur naturally only in the West Indies, in a relict distribution from the Greater Antilles to the Bahamas. At least two species have been extirpated by humans, and the remaining eight species are considered vulnerable to extinction, endangered, or critically endangered (Alberts, 2000). Unfortunately, most aspects of their life history have not been well studied (reviewed in Alberts, 2000) because of their remote locations, their generally small and often highly disturbed populations, and the difficulties associated with studying such large, long-lived lizards.

      Among the least studied aspects of their biology are...

  9. Part III Conservation
    • Introduction
      (pp. 195-198)
      Allison C. Alberts

      Although only sixty of the more than three thousand species of extant lizards attain an adult body mass greater than 1 kg, large lizards represent over two-thirds of lizard species classified as critically endangered (Hilton-Taylor, 2000). There are several reasons why large lizards have been more adversely affected by humans than have small lizards. Small lizards generally have modest-sized home ranges and are able to adapt to the presence of human intervention. In contrast to large lizards, which often require sizeable tracts of undisturbed habitat to survive, many anoles, geckos, fence lizards, and lacertids flourish in urban and suburban environments....

    • 14 Translocation Strategies as a Conservation Tool for West Indian Iguanas: EVALUATIONS AND RECOMMENDATIONS
      (pp. 199-209)
      Charles R. Knapp and Richard D. Hudson

      West indian iguanas of the genusCycluraare among the most endangered lizards in the world (Alberts, 2000). Three species are listed as endangered by the U.S. Fish and Wildlife Service, and the remainder are listed as threatened. Based on IUCN—the World Conservation Union threat criteria, all but four taxa are categorized as either Endangered or Critically Endangered (Hudson, 1996; Hudson and Alberts, this volume). Most species are endangered because much of their tropical dry forest habitat has been eliminated by human development or radically degraded by introduced mammalian species. Many domesticated animals brought by early settlers have become...

    • 15 Testing the Utility of Headstarting as a Conservation Strategy for West Indian Iguanas
      (pp. 210-219)
      Allison C. Alberts, Jeffrey M. Lemm, Tandora D. Grant and Lori A. Jackintell

      Studies on reptiles indicate that larger individuals often survive the neonatal period better than smaller ones because they are more successful at avoiding predation and competing for food (Ferguson et al., 1982; Haskell et al., 1996). This has led to proposals for headstarting programs, in which animals are raised in captivity until they reach a larger and less vulnerable body size, as a conservation strategy for increasing survivorship of reintroduced or translocated individuals. Headstarting programs have not been without criticism, however. In sea turtles, headstarting does not appear to address the fundamental causes of population decline and may impact marine...

    • 16 Survival and Reproduction of Repatriated Jamaican Iguanas: HEADSTARTING AS A VIABLE CONSERVATION STRATEGY
      (pp. 220-231)
      Byron S. Wilson, Allison C. Alberts, Karen S. Graham, Richard D. Hudson, Rhema Kerr Bjorkland, Delano S. Lewis, Nancy P. Lung, Richard Nelson, Nadin Thompson, John L. Kunna and Peter Vogel

      The use of captive-bred or captive-held animals to establish or augment wild populations of endangered species has become a popular yet controversial conservation technique (Griffith et al., 1989; Burke, 1991; Dodd and Seigel, 1991; Reinert, 1991). Such relocation, repatriation, and translocation (RRT) projects have been criticized on the grounds of faulty theory, misguided application, poor implementation, lack of adequate postrelease monitoring, and worse—abuse by profit-driven consultants and development interests (Dodd and Seigel, 1991; Reinert, 1991). Indeed, the myriad problems plaguing RRT efforts demand that they be undertaken only after exhaustive review and lengthy planning; and then, only when such...

    • 17 Conservation of an Endangered Bahamian Rock Iguana, I: POPULATION ASSESSMENTS, HABITAT RESTORATION, AND BEHAVIORAL ECOLOGY
      (pp. 232-257)
      William K. Hayes, Ronald L. Carter, Samuel Cyril, Jr. and Benjamin Thornton

      The bahamian endemicCyclura rileyiis one of the most threatened of the West Indian rock iguanas. Two of its three recognized subspecies,C. r. cristataandC. r. rileyi,are critically endangered, and the third,C. r. nuchalis,is endangered (Alberts, 2000). Although they formerly occupied large islands, today these lizards are confined to small, remote, uninhabited cays of three island groups in the Bahamas (the Exumas, San Salvador Island, and the Crooked and Acklins Islands; figure 17.1). The island groups, each harboring its own subspecies, are on separate banks and therefore were not connected during the most recent ice age when...

    • 18 Conservation of an Endangered Bahamian Rock Iguana, II: MORPHOLOGICAL VARIATION AND CONSERVATION PRIORITIES
      (pp. 258-273)
      Ronald L. Carter and William K. Hayes

      Given the precarious status of two of the three subspecies of the San Salvador iguana(Cyclura rileyi)in the wild (Hayes et al., this volume), consideration should be given to treating these three subspecies as separate management units. The phenetic analysis by Schwartz and Carey (1977) provided the current taxonomy ofCyclura,which recognizes the subspecies ofC. rileyi.Their conclusions were derived largely from assessment of morphological characters, primarily scale counts. More recently, Hollingsworth (1998) and Malone et al. (2000) proposed interspecific relationships based on modern phylogenetic analyses of morphological and mitochondrial DNA (mtDNA) variation, respectively, and both studies...

    • 19 The Role of Zoos in the Conservation of West Indian Iguanas
      (pp. 274-289)
      Richard D. Hudson and Allison C. Alberts

      The iguanas of the west indies are grouped into two genera,Cyclura and Iguana,comprising eighteen taxa that together represent the most highly endangered group of lizards in the world (table 19.1). Although well known, the plight of these imperiled lizards has historically received little attention from zoos worldwide. Although rhinoceros iguanas have been a viable staple of many zoo reptile collections and are responsible for the level of husbandry experience that currently exists for this group, few resources have been devoted to properly managing them in captivity. Faring poorly in traditional zoo settings, these large herbivores require spacious outdoor...

    • 20 Ecotourism and its Potential Impact on Iguana Conservation in the Caribbean
      (pp. 290-302)
      Charles R. Knapp

      Historically, tourists have flocked to a wide variety of Caribbean destinations to enjoy the sun, sea, and sand. Recently, however, Caribbean countries anxious to tap into the growing ecotourism market have attempted to lure travelers to their national parks, which support a vast diversity of wildlife. Thus, ecotourism has become the focus of a growing tourism industry in some Caribbean countries and is being incorporated as an alternative option within the popular traditional markets of others.

      Although several definitions for ecotourism exist (Scace, 1993), the definition used here is “low impact nature tourism which contributes to the maintenance of species...

    (pp. 303-338)
  11. List of Contributors
    (pp. 339-342)
  12. INDEX
    (pp. 343-356)
  13. Back Matter
    (pp. 357-357)