BIOLOGICAL REPORT 97(1) AUGUST 1997 1111111111111111111111111111111 PB98-164833 SYNOPSIS OF THE BIOLOGICAL DATA ON THE GREEN TURTLE CHELONIA MYDAS (LINNAEUS 1758) Fish and Wildlife Service u.s. Department of the Interior .U.s. D~~~~~~~tCo~~~~inerce~ National Technical Information Service Springfield, Virginia 22161 BIOLOGICAL REPORT 97(1) AUGUST 1997 Synopsis of the Biological Data on the Green Thrtle Chelonia mydas (Linnaeos 1758) by Harold F. Hirth Department of Biology University of Utah Salt Lake City, Utah 84112 USA Fish and Wildlife Service U. S. Department of the Interior Washington, D. C. 20240 Preparation of this Synopsis This review of the green turtle, Chelonia mydas, has rnittee aided travel to libraries. Ms. Jeanette Stubbe gra­ been prepared following the FAO fisheries synopsis out­ ciously and conscientiously typed several versions ofthe line of Rosa (1965) and as applied to marine turtles by manuscript. Mr. Kerry Matz prepared the figures. Dr. Hirth (197Ib). John Roth, Chairman of the Biology Department, sup­ The main purposes ofthis synopsis are to bring together ported the author with some sabbatical leave time. the current and salient information on the biology of the It is a pleasure to acknowledge Dr. David W. Ehrenfeld, green turtle and to draw attention to some of the major Dr. Nicholas Mrosovsky, Dr. Mark Nielsen and Dr. Peter gaps in our knowledge of the species. Because of the C. H. Pritchard for their helpful comments after review­ nature of a synopsis, i.e., that of providing an entry into ing an earlier version of the manuscript. the literature, researchers should peruse the original pa­ The author thanks Drs. Leslie Dierauf and Richard pers for details of methodologies and conclusions. Byles, Ms. Susan MacMullin and Mr. Art Needleman of The author is indebted to Ms. Linda Bums, Interlibrary the Endangered Species Office, U. S. Fish and Wildlife Loan Supervisor, University of Utah, for helpful and Service, Albuquerque, New Mexico for help and for sup­ timely assistance in obtaining some rare publications. porting the publication of this synopsis. Assistance from the University of Utah Research Com- ii Abstract This document reviews the salient and current litera­ studies on a few nesting beaches have disclosed signifi­ ture on the biology of the green turtle, Chelonia mydas cant annual fluctuations in numbers of nesters. Under (Linnaeus, 1758) including taxonomy, distribution, physi­ natural conditions there is high predation on eggs and ology, morphology, ecology, demography, exploitation hatchlings and low predation on adults. Long life was and conservation. Fifteen figures and 17 tables supple­ probably the norm for those that survived neonatal mor­ ment the text. tality, before the advent ofhumans. A green turtle survi­ In general, green turtles are large sea turtles well adapted vorship curve is roughly concave, under natural condi­ to marine life. They are circumglobal, commonly occur­ tions. Green turtles are host to a large variety of para­ ring in warm, tropical seas. They occur in offshore wa­ sites, and fibropapillomatosis is a significant disease in ters or on the nesting beaches of at least 139 countries some widely scattered areas. Major food competitors on and territories. Most nesting sites are located between the seagrass pastures are dugongs, fishes and sea urchins. 30° Nand 30° S latitudes. The green turtle is a morpho­ As expected, studies have shown how many aspects of species, made-up of several distinct populations and the turtles' physiology are related to their feeding habits, metapopulations. The total range of a population-en­ reproductive cycles, prolonged swimming, diving and compassing the nesting beach, epipelagic habitat, feed­ migrations. References are provided on morphological ing grounds and migrations-can be very extensive. descriptions ofthe embryo, egg shell, skull, lung, kidney, Sex is determined by substrate temperatures during in­ ovary and oviduct. cubation with warmer temperatures producing females. Some major gaps in our knowledge ofgreen turtles are The diploid chromosome number is 56 and there are no speciation rates, natural sex ratios, ecologies ofhatchlings heteromorphic sex chromosomes. Hatchlings use visual and juveniles during the "lost years", biology of males, cues in crawling to the sea and then, in shallow water, survival rates of different size classes, and navigation they orient by swimming into the waves. Magnetic cues mechanisms. Obtaining information on some of these may be used for orientation in deep water. The cues used parameters can be aided by the development of reliable by navigating adult turtles in their long-distance gametic marking and tracking systems. migrations are unknown. Satellite telemetry may prove Because of many decades of overexploitation by hu­ useful in this regard. Recent mtDNA research supports a mans, most green turtle populations are endangered or natal homing hypothesis. Hatchlings and small juveniles threatened today. Degradation of nesting beaches and are chiefly carnivorous (or omnivorous) while subadults oceanic pollution are additional threats to green turtle and adults are chiefly herbivorous. Trophic level changes survival almost everywhere now. Conservation of any are associated with ontogenetic habitat shifts. one population will almost certainly involve regional co­ Much more is known about females than males because operation. All populations are important because they the former are easily studied on the nesting beaches. Green are the evolving units in nature and because they repre­ turtles are characterized by slow growth, delayed sexual sent genetic diversity. For conservation purposes, each maturity, high fecundity, iteroparity, and a relatively long green turtle nesting population should be viewed as an reproductive life (under natural conditions). Reproduc­ autonomous demographic entity. Preservation of the tive data, from many nesting sites, are provided in tabular turtles' critical habitats, education, and enforcement of form: sizes ofnesters, clutch sizes and number ofclutches existing protective regulations are among the management per season, egg and hatchling dimensions, remigration strategies discussed. intervals and hatching success. Long-range demographic iii Contents Page Preparation of this Synopsis ii Abstract , iii 1. IDENTITy 1 1.1 Nomenclature 1 1.1.1 Valid name 1 1.1.2 Synonymy 1 1.2 Taxonomy 2 1.2.1 Affinities 2 1.2.2 Taxonomic status 2 1.2.3 Subspecies 2 1.2.4 Standard common names 5 1.2.5 Definition of size categories 6 1.3 Morphology 6 1.3.1 External/internal morphology and coloration 6 1.3.2 Cytomorphology 11 1.3.3 Protein composition and specificity and general physiology 12 2. DISTRIBUTION 13 2.1 Total Area 13 2.2 Differential Distribution 14 2.2.1 Hatchlings 14 2.2.2 Juveniles, subadults, and adults 14 2.3 Determinants of Distributional Changes 25 2.4 Hybridization 25 3. BIONOMICS AND LIFE HISTORY 25 3.1· Reproduction 25 3.1.1 Sexuality 25 3.1.2 Maturity 26 3.1.3 Mating 26 3.1.4 Fertilization 29 3.1.5 Gonads 29 3.1.6 Nesting process 30 3.1.7 Eggs 30 3.2 Embryonic and Hatchling Phase 39 3.2.1 Embryonic phase 39 3.2.2 Hatchling phase 39 3.3 Juvenile, Subadult, and Adult Phase 43 3.3.1 Longevity 43 3.3.2 Hardiness 44 3.3.3 Competitors 45 3.3.4 Predators 46 3.3.5 Parasites, commensals and diseases 46 3.4 Nutrition and Growth 55 3.4.1 Feeding 55 3.4.2 Food 56 3.4.3 Growth rate 62 3.4.4 Metabolism 62 iv 3.5 Behavior 64 3.5.1 Migrations and local movements 64 3.5.2 Schooling 71 3.5.3 Responses to stimuli 71 4. POPULATION 72 4.1 Structure 72 4.1.1 Sex ratio 72 4.1.2 Age composition 72 4.1.3 Size composition 72 4.2 Abundance and Density 72 4.2.1 Average abundance and density 72 4.2.2 Changes in abundance and density 72 4.3 Natality and Recruitment 73 4.3.1 Reproduction rates 73 4.3.2 Factors affecting reproduction 73 4.3.3 Recruitment 75 4.4 Mortality 75 4.4.1 Mortality rates 75 4.4.2 Factors causing or affecting mortality 75 4.5 Dynamics ofPopulations 77 4.6 The Population in the Community and the Ecosystem 79 5. EXPLOITATION 79 5.1 Fishing Equipment and Methods 79 5.2 Fishing Areas 80 5.3 Fishing Seasons 80 5.4 Fishing Operations and Results 80 6. PROTECTION AND MANAGEMENT 82 6.1 Regulatory Measures 82 6.2 Management Strategies 84 7. MARICULTURE 87 8. REFERENCES 88 v 1. IDENTITY Chelonia lachrymata Cuvier, 1829: 13. Type-locality, not 1.1 Nomenclature stated. Holotype, possibly in Mus. Nat. Hist. Natur., Paris 1.1.1 Valid name (Roux, pers. comm.). Chelonia mydas (Linnaeus), 1758 1.1.2 Synonymy Chelonia maculosa Cuvier, 1829: 13. Type-locality, not stated; restricted to "Ascension Island" by Smith and Tay­ lor (1950: 17). Holotype, possibly in Mus. Nat. Hist. Testudo mydas Linnaeus, 1758: 197. Type-locality Natur. Paris (Roux, pers. corom.). "insulam Adscensionis". Chelonia bicarinata Lesson, 1834: 301. Type-locality, "1 Testudo macropus Walbaum, 1782: 112. Type-locality 'Ocean atlantique." Holotype, possibly in Mus. Nat. Hist. not stated. Holotype not designated. (illegitimate name). Natur., Paris (Roux, pers. corom.). Testudo viridis Schneider, 1783: 299. Type-locality un­ Chelonia marmorata Dumeril and Bibron, 1835: 546. known, restricted to Charleston, South Carolina by Smith Type-locality, ''lie de l'Ascension." Holotype, Mus. Nat. and Taylor (1950: 17). Holotype not designated. Hist. Natur. Paris 7878. Testudo japonica Thunberg, 1787: 178. Type-locality Euchelys macropus Girard, 1858: 448 (=Testudo mydas "Japan". Holotype not designated. Linnaeus 1758) by monotypy. Testudo marina vulgaris Lacepecte, 1788: 54 and Table. Chelonia formosa Girard, 1858: 456. Type-locality, (illegitimate name; substitute name for Testudo mydas "Feejee Islands". Holotype, U. S. Nat. Mus. 12386, Linnaeus, 1758).