Gulf of Mexico Origin, Waters, and Biota: Volume I, Biodiversity

76. Reptiles (Vertebrata: Reptilia) of the Gulf of Mexico

SixfamiliesofreptileshavespecieslivingintheGulfofMexico (GMx). The 2 families of sea turtles, 5 species, are truly marineanimalsandspendtheirentirelives,withtheexceptionofegglaying ,inmarinewater,oftendistantfromshore. Two emydid turtles and 2 snakes also occur regularly in the Gulf, but peripherally, in near-shore and estuarine habitats. The American crocodile is also an estuarine species, but owing to centuries of human predation, it has only a single viable Gulf population in southern Florida, although survivingspottilyelsewhereintheCaribbeanandSouthAmer ica . In addition, the generally freshwater alligator, Alligator mississippiensis, commonly ranges into upper estuaries of the GMx but is not included here as a marine species. Although 5 sea turtles occur in the Gulf, 2 species, the loggerheadseaturtle(Carettacaretta)andtheKemp’sridley sea turtle (Lepidochelys kempii), are the most common taxa along the north shore. Green sea turtles (Chelonia mydas) occur broadly from north-central Florida coast southward into the West Indies. Hawksbills (Eretmochelys imbricata) regularly live on and around coral reefs, hence they occur mainly in southern Florida, Cuba, and southern Mexico. Leatherbacks (Dermochelys coriacea) are pelagic animals, spending most of their lives in the open ocean; individuals wander into the Gulf occasionally. The leatherback feeds throughout the water column on assorted “jellyfish,” with salps apparently a major item. The other species are bottomfeeders ,mainlyintheshallower(<50m)portionofthe continental shelf; ridleys and loggerheads on crustaceans and larger mollusks, hawksbills on sponges and other sedentary invertebrates, and greens on seagrasses and algae. All sea turtles must return to the beaches to reproduce, returning on multiple-year cycles to their birth (hatching) beach. Since the arrival of man, all have experienced major human predation, and all havegreatly reduced populations and are now legally considered threatened or endangered. This status makes it illegal to handle or possess even pieces of their skeleton when encountered on the beach. Assorted conservationactivitiesandregulationshaveslowedpopulationdeclinesand ,inthecaseofKemp’sridley,havebrought it back from the edge of extinction. For a sea turtle, it is as close to a Gulf of Mexico endemic as possible, with its singlemajornestingbeach(RanchoNuevo)ontheTamaulipas coast and adults confined to Gulf waters. The saltwater crocodile (Crocodylus acutus) is also a threatened species. Its elimination from mangroves and the waterways of other coastal forest can probably be attributed to harvest for the leather trade and the human 1317 76 Reptiles (Vertebrata: Reptilia) of the Gulf of Mexico George R. Zug  Reptilia. After Musick 2002. 1318 ~ Reptiles (Vertebrata: Reptilia) dents throughout the coastal southeastern United States and, thus, occur in marsh and swamp habitats adjacent to the Gulf. Further, populations of cottonmouths persist on coastal islands where the only source of fresh water is rainwater. Such populations occasionally occur on islands in association with bird rookeries where the snakes apparently feed seasonally on the fish dropped by adult birds as they feed their nestlings. Abbreviations Abbreviations for Habitat-Biology: est = estuaries; msp = mangrove swamps; ner = neritic; plg = pelagic; smr = salt marshes; THR = threatened or endangered; tst = tidal creeks/streams. The classification and nomenclature used herein follows that of the Catalogue of American Amphibians and Reptiles, similar to that used by Smith (1954) in the original Bulletin 89. Genera and species are listed alphabetically within families. References 1. Bolton, A. B., and B. E. Witherington, editors. 2003. Loggerhead Sea Turtles. Smithsonian Books, Washington, D.C. 319 pp. 2. Dodd, C. J. Jr. 1988. Synopsis of the biological data on the propensity to remove any large, competing predator. It preys on assorted vertebrates, fish apparently the major prey in most localities. Like sea turtles, it is an egg layer and must lay its eggs in sand or, if lacking, a self-made heap of vegetation and soil. Unlike sea turtles, males and females regularly haul ashore to bask. Of the 4 smaller species of reptiles, 2 (saltwater terrapin , Malaclemys terrapin, and saltmarsh water snake, Nerodia clarki) are obligate residents of seaside habitats, even though the water snake is poorly adapted physiologically for living in saltwater. This snake spends much of its time out of water but beneath cover, nocturnally foraging for fish. It is a live-bearer. In contrast, the terrapin spends much of its time in water, even hibernating there in more northerly areas. Terrapins have a catholic diet centered on invertebrates, with bivalve mollusks high on their list of preferences. They are egg layers and require nesting sites in friable soil well above the high-tide line. The final 2 reptiles, cooters (Pseudemys, several species ) and cottonmouths (Agkistrodon piscivorus), are freshwater taxa with only occasional incursions into marine habitats. Cooters are typically turtles of large bodies of water, and whether accidentally or intentionally, they are found occasionally feeding on marine vegetation in saltwater flats adjacent to river mouths. Cottonmouths are fish-eaters and streamside and lakeside resiReptilia . After Musick 2002. Reptilia. After Musick 2002. Reptilia. After Musick 2002. Reptilia. After Musick 2002. Zug ~ 1319 10. Iverson, J. B. 1992. A Revised Checklist with Distributional Maps of the Turtles of World. Privately printed, Richmond, Indiana. 363 pp. 11. Pritchard, P. C. H. 1980. Dermochelys coriacea. Catalogue of American Amphibians and Reptiles 238: 1–4. 12. Ruckdeschel, C., C. R. Shoop, and G. R. Zug. 2000. Sea turtles of the Georgia coast. Occasional Publications of the Cumberland Island Museum 1: i–x, 1–100. 13. Smith, F. G. W. 1954. Taxonomy and distribution of sea turtles. Pp. 513–515 in P. S. Galtsoff, ed. Gulf of Mexico, Its Origin, Waters, and Marine Life. Fishery Bulletin 89. Fishery Bulletin of the Fish and Wildlife Service, Vol. 55, Washington, D.C. 14. Spotila, J. R. 2004. Sea Turtles. A Complete Guide to Their Biology, Behavior, and Conservation. Johns Hopkins University Press, Baltimore. 227 pp. 15. Wilson, R. V., and G. R. Zug. 1991. Lepidochelys kempii. Catalogue of American Amphibians and Reptiles 509: 1–8. 16. Witzell, W. N. 1983. Synopsis of biological data on the hawksbill turtle Eretmochelys imbricata (Linnaeus, 1766). FAO Fisheries Synopsis 137: i–iii, 1–78. loggerhead sea turtle Caretta caretta (Linnaeus, 1758). U.S. Fish and Wildlife Service, Biological Report 97: i–viii, 1–110. 3. Dodd, C. J. Jr. 1990. Caretta caretta. Catalogue of American Amphibians and Reptiles 483: 1–7. 4. Ernst, C. H., and R. B. Bury. 1982. Malaclemys, M. terrapin. Catalogue of American Amphibians and Reptiles 299: 1–17. 5. Ernst, C. H., and E. M. Ernst. 2004. Snakes of United States and Canada. Smithsonian Books, Washington, D.C. 668 pp. 6. Ernst, C. H., J. E. Lovich, and R. W. Barbour. 1994. Turtles of the United States and Canada. Smithsonian Institution Press, Washington, D.C. 578 pp. 7. Ernst, C. H., F. D. Ross, and C. A. Ross. 1999. Crocodylus acutus (Cuvier). Catalogue of American Amphibians and Reptiles 700: 1–17. 8. Hirth, H. F. 1980. Chelonia mydas. Catalogue of American Amphibians and Reptiles 249: 1–4. 9. Hirth, H. F. 1997. Synopsis of the biological data on the green turtle Chelonia mydas (Linnaeus 1758). U.S. Fish and Wildlife Service, Biological Report 97: i–v, 1–120. Submitted: April 2006 Accepted: April 2006 1320 ~ Reptiles (Vertebrata: Reptilia) Taxonomic summary for reptiles of the Gulf of Mexico. Orders Total Species Number endemic species Number nonindigenous species Testudines 6 0 0 Squamata 2 0 0 Crocodilia 1 0 0 Totals 9 0 0 Checklist of reptiles (Vertebrata: Reptilia) from the Gulf of Mexico. Taxon HabitatBiology Depth (m) Overall geographic range GMx range References/ Endnotes Order: Testudines Family: Cheloniidae Caretta caretta (Linnaeus, 1758) ner, THR 0–20 Worldwide entire 1, 2, 3, 7, 10, 14 Chelonia mydas (Linnaeus, 1758) ner, THR 0–20 Pantropic se, sw 7, 8, 9, 10, 12, 14 Eretmochelys imbricata (Linnaeus, 1766) ner, THR 0–20 Pantropic entire 7, 10, 12, 14, 16 Lepidochelys kempii (Garman, 1880) ner, THR 0–20 GMx and N Atlantic entire 7, 10, 12, 14, 15 Family: Dermochelyidae Dermochelys coriacea (Vandelli, 1761) plg, THR 0–50 Pantropic entire 7, 10, 11, 12, 14 Family: Emydidae Malaclemys terrapin (Schoepf, 1793) est, tst 0–5 GMx and W Atlantic USA se, ne, nw 5, 7 Order: Squamata Family: Natricidae Nerodia clarki (Baird & Girard, 1853) msp, smr 0–2 E Florida to Central Texas ene, nne, nnw 4 Family: Viperidae Agkistrodon piscivorus (Bonnaterre, 1790) msp, smr 0–2 SE North America ene, nne, nnw 4 Order: Crocodilia Family: Crocodylidae Crocodylus acutus (Cuvier, 1807) msp, THR, tst 0–3 Trop. E Pacific, Caribbean ese, ene 6 ...