78 CuEI-oNten CousenvertoN axl BIot-ocv, Volmne 2, Ntunber I - 1996 Moll. D. 1991. The ecology of sea beach nesting in slider turtles (Truc'herl.\'.r sc'r'iptct venustct) from Caribbean Costa Rica. Chelon. o, ee6 n, .,1'Jill,i;X'fJ:J:fi loun,rn,ion Conserv. Biol . l(2): 107- I 16. Moll. E.O. 1978. Drumming along the Perak. Nat. Hist. 87:36-43. Occurrence and Diet of Juvenile MoRluER. J.A. 1982. Factors influencing beach selection by Loggerhead Sea Turtl es, Caretta caretta, in nesting sea turtles. In: Biorndal, K. (Ed.). Biology and Conser- vation of Sea Turtles. Washington D.C.: Smithsonian Institution the Northwestern Gulf of Mexico Press. pp. 45-5 I . MullEn. G.B., AND WRGNER, G.P. 1991. Novelty in evolution: PaunlA T. Plorxtnl restructuring the concept. Ann. Rev. Ecol. Syst. 22:229-256. AND 1980. rnigrations of the I Oeeano, M.E.., Bnoors, R.J. Nesting Depu rtment o,f Bictsc'iertc'e urrcl B iotet'ltnol og\,, snapping tr-rrtle (Chelydro serpentina). Herpetologica 36: 158- D rexe I (J nit,e rs i'l, 32ucl uncl C lte stnut St re et s, P lti I crcl e I p lt i u, t62. Penns\lvmicr 191 04 USA IFu.r: 2 I 5-895- ] 273l Ossr, F.J. 1986. Turtles, Tortises and Terrapins. New York: Saint Martin's Press 231 pp. , Subadult loggerheads (Ca rettct carettcr) are the most PnlnnrNo, F.V.., O'CoNNoR, M.P., AND Sporlla, J.R. 1990. Metabo- common sea turtles in the northwestern Gr,rlf of Mexico lism of leatherback turtles, gigantothermy, and thermoregula- (Hildebrand, where feed tion of dinosaurs. Nature (London) 344:858-860. 1983), occurring nearshore they PnrrcHnnn, P.C.H. 1979. Encyclopedia of Turtles. Neptune, N.J.: primarily on benthic invertebrates (Plotkin et al., 1993). T.F.H. Publications, 895 pp. Adult loggerheads also occur in the northwestern Gulf PnrrcHnno, P.C.H., RNo Tnneseu, P. 1984. The Turtles of Venezu- but appear to be less abundant than subadults, dcl not ela. Soc. Stud. Amphib. Rept. Contr. Herpetol. No. 2,,403 pp. re-qlllarly nest on any beach in this region (Dodd, 1988; of Rersz, R.R., AND LnuntN, M. 1991. Owenettct and the origin Shaver, 199 I ), and presLlmably migrate to rookeiries in (London) turtles. Nature 349:324-326. the eastern Gulf of Mexico or the western Atlantic Ocean, RuoprN, A.G.J. I 985. Cornparative chondro-osseous developtnent includin-e the Caribbean Sea (Meylan, 1982; Dodd, 1988 ). and growth of marine turtles. Copeia 1985:152-77 l. A few documented reports of post-hatchling and jr.rvenile RHoptN, A.G.J., MtttpRMEtER, R.A., AND HRLL, P.M. 1993. Distri- the northwestern of Mexico. bution, osteology, and natural history of the Asian giant soflshell loggerheads exist from Gulf turtle, Pelochelys bibroni, in Papua New Guinea. Chelon. most of which come from individuals stranded on the Conserv. Biol. l(l ): l9-30. Texas coast within the size range (< 40 cm curved RoslttsoN, G.D., AND DuNsoN, W.A. 1916. Water and sodium carapace length) once referre d to as the "lost year," but balance in the estuarine diamondback terrapin (Molaclemts). J. more recently termed "pelagic sta-ee" (Carr, 1986, 1987 ). Comp. Physiol. I 05 :129-152. Pelagic stage lo-egerheads are known inhabitants of SeroEL, M.E. 1975. Osmoregulation in the turtle Triony-r sltini.feru,s driftlines and convergence zones where they find refuge fi'om brackish and freshwater. Copeia l9l5:124- 128. and food in Srl rgossltm and other items that accumulate TERL, J., RNo TERL, M. I 969. Life and Death of the Salt Marsh. New in these surface circulation features (Fletemeyer, I978. York: Ballantine Books,274 pp. Den Harto-{, Venunu, G.J. 1995. Econornics, volcanoes', and Phanerozorc revo- Carr and Meylan, 1980; Van Nierop and lutions. Paleobiol. 2l : 125- 152. 1984; Carr, 1986; Richardson and McGillivary, 199 I ; Wnlrcen, W.F. 1913. The locomotor apparatus of Testudines. In: Witherington, 1993). Pelagic stage loggerheads are rare Gans, C., and Parsons, T.S. (Eds.). Biology of the Reptilia. Vol. in US waters (Carr, 1986), but recent strandings in Texas 4. New York: Academic Press, pp. l- 100. suggest they may be more common than previously Woop, R.C. 1912. A fossil pelomedusid turtle from Puerto Rico. believed (Plotkin, 1989). Breviora392:l-13. Between 1981 and 1993 I examined I 0 j uvenile of Bctntuc'helys congolertsis, a Wooo. R.C. 1975. Redescription loggerheads that were stranded on the south Texas coast fossil pelomedisid turtle f}om the Paleocene of Africa. Rev. (Mustang Island, North and South Padre Islands). I mear- ZooL Africa 89: 128-141. sured curved carapace length (CCL) and noted the Wooo, R.C. 1976. Stupenclenlvs g,eogrulthicus, the world's largest -eeu- eral condition of each turtle. I performed necropsies ou turtle. Breviora 436: l-3 I . Woon, R.C. 1917. Evolution of emydine turtles Grctptenn's and seven dead specimens, collected and preserved digestive Malaclenl\:s (Reptilia, Testudines, Ernydidae). J. Herpetol. tract contents in I07o buffered formalin, and identified I l:415-421 . food items to the lowest taxon possible. Three live turtles ZnNcEnL, R. 1953. The vertebrate fauna of the Selma Formation of were generally in poor physical condition and were held Alabarna. Part 3. The turtles of the farnily Protostegidae. Part 4. in captivity, rehabilitated, and then released. The results The turtles of the family Toxochelyidae. Fieldiana Geol. Mem. of these studies are presented in Table I . 3:61-211 . The size of the loggerheads I examined ranged from ZnNcEnL, R. 1980. Patterns of phylogenetic differentiation in the 10.8 32.5 (r 20.7 cffi, SD 8.7). These toxochelid and cheloniid sea turtles. Amer. Zool.20:585-596. to cm CCL = -- size ZnNcEnL, R., AND Slonx, R.E. I 960. A new specimen of juvenile loggerheads are within the pelagic stage Desmatochelt's loyt,i Williston, a primitive cheloniid sea turtle range which Carr ( 1986) reported missing from US f rom the Cretaceous of South Dakota. Fieldiana Geol . 14(3):1 -40. waters and which are abundant in the eastern North Atlantic Ocean near Madeira and the Azores (Bolten et Receit'ecl: 2 November I 994. Ac'c'eptecl: 2 May 1995. al., 1993). Carr's ( 1986) dispersal scenario for neonate NorEs AND FrEr-n Rpponrs t9 loggerheads originating from US Atlantic ocean rooker- March are located in French Guiana and Braztl (Dodd, ies, based on dominant surface circulation patterns of the 1988). The intermediate sized loggerheads (turtles 3-6) North Atlantic Ocean, accounts for the apparent absence were hatched either during the year they were stranded or of pelagic stage loggerheads in US waters. Accordin_e to in the year prior to stranding. Their origin is probably a Carr's ( 1986) hypothesis (recently supported in parr by rookery from the Florida Gulf coast, the Caribbean, or Bolten et al ., 1993), neonate loggerheads cross the Atlan- South America. The lar._eest log..eerheads (turtles 7-10) tic Ocean, travel the circuit of the North Atlantic Gyre, were hatched at least one or more years prior to stranding and eventually return to US waters where they are re- and could have ori-einated from any loggerhead rookery !-rLlited into nearshore benthic habitats. The origin of the in the eastern Gulf of Mexico, western Atlantic Ocean, or Iuvenile loggerheads I examined is unknown, but it is Caribbean Sea. :resumed that they originated from rookeries located Di-qestive tracts of the 9 srnallest lo.-egerheads exam- : l:ervhere, because there are virtually no loggerhead ined contained Sargassun'r, pela-eic crustaceans and mol- :re sting sites in the northwestern Gulf of Mexico (see h"rsks, flotsam, and anthropogenic plastic debris (Table :nap of loggerhead nesting locations in Dodd, 1988). 1), indicating they had been feeding in upper surface Based on oceanographic features of the Gulf of waters. This is consistent with previous observations of \lexico, there are several plausible scenarios that may pelagic stage loggerheads (see Dodd, 1988, for review). :.rplain origin(s) of and route(s) travelled by juvenile Digestive tract contents of the largest loggerhead I exam- 1q'rg-gerheads to Texas Gulf beaches (see Carr, 1986, and ined (turtle 10, 32.5 cm CCL) were different from the Collard, 1987,, for review). The first hypothesis is that others, &S it had been foraging on benthic sea pen ireonate loggerheads from Florida Gulf coast rookeries (Vi rgularia presbt'tes). Subadult and adult log_eerheads :ravel westward and eventually reach the western Gulf of (5 I to 105 cm CCL) in the northwesrern Gulf of Mexico \lexico. An alternative hypothesis is that neonate log- are nearshore benthic foragers that feed predominantly lerheads frorn US Atlantic coast rookeries travel in the on sea pen in 6 to 12 m water deprh (Plorkin et al., 1993). \orth Atlantic Gyre and return to US Atlantic waters, Further evidence that turtle 10 was post-pelagic stage e ntering the Gulf of Mexico via the Yucatan current. and already resident in the benthic community were Lastly, it is possible that these loggerheads originated numerolls turtle barnacles ( Chelortibiu testutlinurict) at- from a rookery outside the US (i.e., the Caribbean. tached to its carapace. Turtle barnacles are common ce ntral America, or South America [Dodd, 1988]) and commensals of subadult and adult loggerhead turtles cntered the Gulf of Mexico via the Yucatan current. The from this region but are rarely seen attached to pelagic t\\'o srnallest loggerheads (Table I ., turtles I and 2) were stage tr"rrtles (pers. obserr,.). It is unknown when logger- probably from South American rookeries because their heads leave the pelagic stage or what prompts this shift size indicates that they were only a few weeks post- in habitat and resource use.