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Overview
In addition to providing sixty-five full-color photographs of juveniles and adults along with forty-two colorfully detailed distribution maps, this volume features an introductory section explaining the physiography, climate, and habitats of the state, and offers illustrated taxonomic keys for all the species considered, including the oceanic behemoths that lay their eggs on Alabama's gulf beaches and the lumbering gopher tortoise that provides safe haven for countless other animals and arthropods in its underground burrows of the Coastal Plain. With fine line drawings to highlight various distinguishing attributes of the animals, this volume is the definitive guide to the state’s fascinating and diverse turtle populations—freshwater, marine, and terrestrial.
Although they are notoriously slow-moving, turtles still survive on Earth because of their remarkable adaptations—an exterior shell for body protection, long lives, high reproductive output, stamina, and a capacity for doing without. Turtles are cold-blooded reptiles that were here long before mammals, and they're still around, continuing to adapt to many different habitats and ecological niches, still interbreeding, evolving, and speciating. Turtles of Alabama is a fitting celebration of that phenomenal variety and strength.
Product Details
| ISBN-13: | 9780817388171 |
|---|---|
| Publisher: | University of Alabama Press |
| Publication date: | 10/15/2015 |
| Series: | Gosse Nature Guides , #5 |
| Sold by: | Barnes & Noble |
| Format: | eBook |
| Pages: | 304 |
| File size: | 60 MB |
| Note: | This product may take a few minutes to download. |
About the Author
Read an Excerpt
Turtles of Alabama
By Craig Guyer, Mark A. Bailey, Robert H. Mount
The University of Alabama Press
Copyright © 2015 the University of Alabama PressAll rights reserved.
ISBN: 978-0-8173-8817-1
CHAPTER 1
Species Accounts
The remainder of this book describes turtles as a major radiation of amniotes (terrestrial, egg-laying, or live-bearing vertebrates), each family of turtles found in Alabama, and each of the state's species within each family. Presentation of each family, genus, species, and subspecies is in the order of appearance within the keys provided rather than listed alphabetically. Important genetic variation supported by published analyses is discussed within each species account. Each species or subspecies account has distinct sections that we describe below.
KEYS
Keys are tools designed to aid in identification of organisms. These tools present paired descriptions, one of which will conform to an individual organism of interest and the other of which will not. At the end of each consistent description is a number indicating the next couplet to be considered. This process of making dichotomous choices is followed until a final description identifying the organism of interest is reached. We include taxonomic keys for the turtles of Alabama and take the unusual step of dispersing these keys throughout the accounts rather than including a single key. We do this to place information close to sections of text for which the keys are most useful. Keys to the families of turtles appear at the end of the description of the group Testudines. When necessary, keys to genera are placed at the end of the description of each family, keys to species appear at the end of descriptions of each genus, and keys to subspecies are placed at the end of the Taxonomy section of the appropriate species account.
NAMES
The generic, specific, subspecific, and common names applied are, in most cases, those listed in Crother (2012). However, we have taken the liberty to elevate Apalone mutica calvata to species status because all current evidence supports this status and only taxonomic inertia has prevented the action previously.
PHOTOGRAPHS
We have benefited from the talents of a large number of photographers. Where possible, we have selected images that show key features. When the location of the specimen photographed is known, we identify it.
DESCRIPTIONS
Our descriptions are intended to provide sufficient information to enable the reader to distinguish a particular taxon from all others occurring within the state. Each description is based on a composite of specimens representing variation within Alabama and surrounding states. But, because nature is variable, it should be kept in mind that occasional individuals belonging to the described taxon will not conform to the descriptions presented here.
ALABAMA DISTRIBUTION
In addition to a general statement describing the distribution of each taxon occurring within Alabama, a distribution map is included. For each map, we include diagonal hatching intended to delineate the presumed range at the state level. As these data are incomplete for most taxa, our estimated ranges should not be expected to be entirely accurate. Maps for species thought to occur statewide lack hatching. Known occurrences are presented as red dots on a Herpetofaunal Regions base map and readers may use these, along with the discussion in the text, as further clues to overall distribution. These red dots depict specific locations for (a) specimens the authors have examined, (b) photo-vouchered specimens submitted to the Alabama Herp Atlas Project (a web-based program of citizen science records stored at AUM), (c) occurrences documented in the databases of the Alabama Natural Heritage Program and/or ADCNR State Lands Division, Natural Heritage Section, and (d) literature records believed valid. Each record was georeferenced and plotted to the greatest possible precision using ArcGIS® software by Esri. Purple dots indicate specimens found displaying evidence of hybridization or intergradation with another species/subspecies. The state distribution maps also include insets showing the approximate distribution of each taxon within the continental United States or Gulf Coast. These are modified and customized from a number of previously published distribution maps, particularly those developed for Elliot et al. (2008).
HABITS
Here we provide information on habitat selection, seasonal patterns of activity and reproduction, mating strategies of males and females, major diet items, and habitat associations. In general, this section is designed to summarize where and when each species is likely to be active and what activities make the species detectable by humans. Additionally, we describe the timing and duration of each major growth stage in the life cycle of each turtle species.
CONSERVATION AND MANAGEMENT
In this section we describe the current conservation status of each species in Alabama. Alabama's turtles are generally threatened by habitat loss and fragmentation, loss of natural community integrity, and direct persecution. Because conservation issues are likely to increase in the future, we summarize management activities that might imperil each species as well as those activities that are likely to enhance populations. Similar data are provided for species that have conservation status within the state, and for these we provide information on key public properties that will play crucial roles in long-term maintenance of Alabama's imperiled turtles. In developing its 2005 State Wildlife Action Plan, or SWAP, (Alabama Department of Conservation and Natural Resources, Division of Wildlife and Freshwater Fisheries 2005), the State of Alabama used the findings from its 2002 Nongame Symposium, which assembled scientific experts to compile the best data on Alabama's wildlife, and used those data to identify those species most in need of conservation action. The Third Nongame Symposium's Amphibian and Reptile Subcommittee identified eleven turtles as being of immediate conservation need (Priority 1 or 2, on a scale of 1 to 5 as described in Mirarchi et al. 2004), and we summarize the subcommittee's recommendation in each species account.
TAXONOMY
We accept the concept that species are lineages that are discovered through careful analysis of variation in the characteristics of organisms. These discoveries arise from creation of phylogenetic trees built from character data. Under this species concept, any diagnosable terminal branch is sufficient to discover a new species. Additionally, we accept the concept that taxonomic groups at any level of classification should be monophyletic. In practice, ancestral species might survive through the branching process, generating some lineages that are difficult to diagnose (de Queiroz 1998). Such species present challenges for determining species boundaries, and the decisions that we make for the boundaries of Alabama's species undoubtedly will suffer from this challenge.
For turtles, color patterns, conformation of scutes, counts of scales, and shapes of appendages are external features that traditionally have been used to diagnose species, genera, and families. To these traditional characters we have added information from publications describing the mitochondrial and nuclear genomes. These characters have the advantage of allowing rapid development of data sets that are much larger than those based on morphology. The mitochondrial genome is inherited in offspring entirely from the female side of the family tree, while the nuclear genome captures information about gene flow associated with both parents. For this reason, phylogenetic trees based on the mitochondrial genome are not guaranteed to be concordant with those based on the nuclear genome. Nevertheless, published data on the mitochondrial genome often are assumed to carry phylogenetic information, in the absence of data to the contrary. Because these mitochondrial data are cheap to generate, are voluminous, and typically tell an evolutionary story that is consistent with the nuclear genome, we accept them as providing evidence of inter- and intraspecific evolution. These data are particularly important in phylogeographic studies, a field of biogeography that uses patterns of evolution within species that are discernible by analysis of molecular data. Such studies are becoming increasingly common for Alabama's turtles, and the intraspecific lineages generated by such studies likely allow the discovery of new lineages that were not evident from analysis of traditional morphological data. This creates an exciting environment for taxonomists because so many new lineages may be species available for discovery, and such discoveries tell us important stories about how Alabama's rich biodiversity was generated (e.g., Soltis et al. 2006). It also creates a stressful environment for authors of field guides, such as this one, because of the likelihood that the guide will be obsolete before it is published. Nevertheless, we attempt to describe all lineages supported by character data of any kind, and, therefore, that might indicate speciation events awaiting taxonomic recognition.
CHAPTER 2Turtles — Testudines
Turtles, as a group, are our oldest living amniotes, having been on the earth for at least 220 million years and having diverged from the common ancestor to all other lineages 280 million years ago. While varying considerably in size, shape, and color, all turtles are easily recognizable as such. Each species has a shell that consists of an upper portion, the carapace, which joins laterally with a lower portion, the plastron. A close inspection of the shell of most turtles will reveal an inner layer of bony plates created by modified ribs, vertebrae, and elements of the sternum, and an outer layer of horny epidermal scutes. These structures characterize all turtles possessing a hard shell. The shell becomes modified in two radiations of turtles that have soft shells. In these forms, the bony elements are greatly reduced, and the outer layer of the shell is composed of leathery skin rather than hard epidermal scutes.
Besides the shell, turtles have a number of other unique features. Primary among these is the use of specialized neck muscles to ventilate the lungs. The rib cage in most amniotes is designed to expand and contract, creating a pump mechanism to draw air into the lungs and then to force it out of the lungs. Because the ribs of turtles are solidly fused to the shell, neck muscles take over the role of lung ventilation by creating a bellows apparatus at the base of the neck. Associated with this change in anatomical structure, the shoulder girdle of turtles has moved from a position outside the rib cage, where it is positioned in all land vertebrates except turtles, to a position inside the rib cage. The sum total of changes that characterize living turtles has created a radiation that is immediately identifiable to all human cultures.
The life histories of turtles vary in details but are similar in basic aspects. All species are oviparous, laying eggs in leaf litter or, more frequently, in a cavity that the female digs in loose soil. Fertilization is internal, accomplished by means of a penis that is extruded from the vent of the male at the time of copulation and inserted into the cloaca of the female. Courtship activities prior to copulation vary, and the details of this behavior are known for relatively few species. In general, these courtship behaviors involve displays given by the male turtle to a female. Although not yet documented by careful study, females clearly use these courtship behaviors to select from among several competing males. In River Cooters (Pseudemys) and Painted Turtles (Chrysemys), the male gives a tactile cue by stroking the head of the female with elongate claws on his front limbs while swimming in front of her. In Gopher Tortoises, courtship is accompanied by visual cues (head-bobbing on the part of the male), tactile cues (biting of the female's head and anterior carapace by the male), and chemical cues (rubbing of exudates from subdentary glands by males and females onto their own and their partner's forelimbs). Occasionally, male Gopher Tortoises may pound the side of the female's shell with the front end of his plastron. Male Eastern Box Turtles bite and nip at the front of a female's carapace during courtship. Males of some Map Turtles (Graptemys) vibrate their head against the top and sides of a female's head; in other male Graptemys, claws are used in a manner similar to males of Pseudemys.
Because courtship activities of a male are designed to gain the attention of a female, female turtles appear to choose from available male turtles by maintaining or breaking off that attention. For example, in Slider Turtles (Trachemys), females frequently avoid interactions with courting males by diving underwater. If a male is selected, the female signals her choice by rapidly opening and closing the nictitating membrane, an opaque eyelid-like structure found in diving reptiles, which gives a white flash when closed. In Gopher Tortoises, females may ram courting males or may break off courtship by entering a burrow. If she selects a mate, then a female Gopher Tortoise signals this selection by walking backward while turning her back to the male.
Once selected by a female mate, the male turtle typically mounts the female from the rear, twisting his tail beneath hers. In several species of turtles, the male's plastron has a concavity that facilitates assumption of the copulatory position. This plastral concavity is especially pronounced in male Box Turtles, but is noticeable also in male Gopher Tortoises and Eastern Mud Turtles. Male turtles may hold on to the female's shell with all four feet, with just the hind feet, or with the feet and tail. The tails of male mud and musk turtles are adapted to hook under the female's carapace during copulation, locking male and female turtles together. In back of the knee of the hind leg of males of these genera are opposable patches of horny skin in which the tail of the female is grasped and pulled to one side.
In all species of Alabama turtles, a nest cavity is excavated by the female using her hind feet. In some cases the female expels fluid from the bladder during the process; this softens the soil and makes digging easier. Some nests are never completed, either because the soil is not soft enough for digging or because incomplete nests fool predators as to the location of real nests. For complete nests, a female deposits eggs and then covers them using only the hind feet and smoothing the top of the nest with her plastron. The female then leaves the nest, providing no further parental care.
The shell of turtle eggs is composed of protein with aggregations of calcium. Tortoises, soft-shelled turtles, and musk and mud turtles have hard shells because of increased calcium concentrations and complex organization of the calcium. The shells of these eggs are white in color and have hard surfaces, as in chicken eggs. The remainder of Alabama's turtle species produces eggs that are soft and leathery because the calcium is in low concentrations and is unorganized in structure. These shells often are tan in color.
Sexual dimorphism is evident in most species of turtles. The tail of a male is longer and thicker than that of a female. The vent of a male is usually well beyond the edge of the carapace when the tail is extended, whereas in a female the vent is under the carapace. In most turtle species, an adult female attains a greater size than an adult male. Size difference is especially pronounced in some species of Map Turtles in which the female may be 2.5 times larger than the male. In these species the females not only exceed the males in size, but, in most females, develop greatly enlarged heads, a change that does not occur in the males. However, there are unusual cases in Alabama's turtle fauna in which the male grows to a larger size than the female (Snapping Turtles [Chelydra and Macrochelys]), or are approximately equal in size (Gopher Tortoise).
Sexual dichromatism also can be pronounced in some turtles. In soft-shelled turtles, the juvenile carapace pattern is often pronounced and includes large dark spots or dark rings along the edge of the back half of the carapace. In some species, males retain this juvenile coloration while females become uniform in color. In Red-eared Sliders, the reddish bar on the side of the head is retained well into adulthood in most females, but becomes obscured by melanism in most adult males.
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Excerpted from Turtles of Alabama by Craig Guyer, Mark A. Bailey, Robert H. Mount. Copyright © 2015 the University of Alabama Press. Excerpted by permission of The University of Alabama Press.
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