The Northwestern Gulf of Mexico

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. Turtle l0 is one of the hatching (Dodd, 1988), and the only known areas where smallest loggerheads ever recorded foraging in a benthic 1o-egerhead hatchlings are produced from January through habitat and probably represents the lower end of the size range at which loggerheads are recruited from pela_eic to Table l. Date and location of stranding, curved carapace length nearshore benthic feeding grounds. tCCL, in cnr),, and digestive tract contents of juvenile loggerhead The number of pela,-eic sta-ee lo._9.-gerheads found tLtrtles (Carettu c'urettrr) stranded on the south Texas coist (MJ = stranded on Texas Gulf beaches sLl-e-gests they may be \4ustang Island, NPI = North Padre Islancl, Spl = South padre Island). Pelagic vs. benthic stage s deternrirred by dietary analysis. more abundant in US waters than prel;iously believed and that the Gulf of Mexico may be irnporranr develop- Turtle Date Locartion CCL Digestive tracr conter-rts nrental habitat. Alternatir,'el\,. the temporal distribr.rtion Pelu.qic Stuge of the lo-e-gerhead strandings slr-9-eests their occurrence "grolrp" I l7 Apr 1988 MI I0.8 Sru,qrr,r.sunt. Jutrtltirrrr (purple lnitv be a rare event. Six of the specimens I sea snaiI). jellyfish. ballot.rn. e\anrined hacl stranded in the sallte _qeo.-qraphic area latex rr-rbber. aluntinLlnt loil. clurins a discrete tinre periocl (April, 1988) and may have hard plastic 2 27 Apr 1988 MI I t.2 not exanrined beelt tl'alt\ported irt the sanre water ffrass before coming 3 l0 Jun I 988 MI r4.8 not exarnined ashol'e. Uttu\Llal or fluctLlatin._q oceanic conditions may -l 1987 SPr 16.0 Su r g us.\ f uttt. bird eathers. coltcentrate pela_eic sta_qe loggerheads in the northwest- woody vegetation

5 17 Apr 1988 NPI r 6.0 Su r g et.s,\ J r I t i uttt . urt n u . j styrofbam : :l,:i: I .':', l';; :." -il :, I; : ?,3::' J: LT[l i? il 5l: 6 23 Apr 1988 NPI 16.5 Surgu,sslun,stornatopod anrl decapod larvae. barnacle cirri. bird feathers. woocly vegetatiorr ,\ckttov'ledgmenls. - Fundin-e and institutional sup- 7 9 Apr 1988 MI 26.6 not examinecl port w'ere provided in part by the University of Texas 8 8 Apr 1988 NPI 30.0 Sarga,s,rrln,jellvfish. stvrotoanr Marine Science Institute, the National Marine Fisheries 9 5 Apr 1993 NPI 32.4 Sargus.tunt, plastic bar_u pieces Service - Galveston Laboratory, Sigrna Xi - The Scien- Benthic Stage tific Research Society, and Sea Turtles, Inc. I also wish l0 27 Apr (sea 1992 MI 32.5 Vir.qulctriu presbt'te.r pen ) to thank Tony Amos and Donna Shaver for their help 80 CHnloNrAN CoNSERVATToN AND BtoLoGv, Volume 2, Nuntber I - 1996 collecting stranded turtles and James R. Spotila and C t rc t o n i'lm C o'l 8 o-8 2 Dave Penick for their comments on an earlier version of ;;'u:;: l, iff '-?::;fi ,1ff ffi [ I this manuscript. First Record of Heosemys spinosd from the Literature Cited Philippines, with Biogeographic Notes

IxnnalqBu, Dnsl'2 BolrEN, A.8., MRRtrNs, H.R., BIoRNDAL, K.A., AND GonnoN, J. 1993. Size distribution of pelagic-stage loggerhead sea turtles I (Caretta carettn) in the waters around the Azores and Madeira. Centre .for Herpetologv, Madrcrs Crocodile Bank Trust, Arquipelago I I A:49-54. Post Bctg 4, Mantallapurcun 603104 India; )Present Cnnn, A.F., Jn. 1986. New perspectives on the pelagic stage of sea Acldress: Musemn o.f Contparative Zoologt, Hqrvsrd turtle development. NOAA Tech. Mem. U.S. Dept. Commerce Universin,, Carnbridge, Mcrssachusetts 02 I 38 U SA NMFS.SEFC- 190. CnRR, A.F., JR. 1981. Impact of nondegradable marine debris on Heosentys spinosa, the spiny turtle, is a widespread the ecology and survival outlook of sea turtles. Mar. Poll. Bull. southeast Asian batagurid, distributed from Tenasserim in I 8:352-356. southern Myanmar, south to the tip of the Malay Peninsula, CenR, A.F., JR., AND MEvuN, A.B. 1980. Evidence of passive and also on the islands of Sumatra, Borneo, and Natuna migration of green turtle hatchlings in sargassum. Copeia (Smith l93l; Pritchard, 1979; Iverson, 1992). It is appar- 1980:366-368. , absent from Indo-China, and not previously known Corrnnp, S.B . 1987. Review of oceanographic features relating to ently neonate sea turtle distribution and dispersal in the pelagic from the Philippines. environment: Kemp's ridley (Lepidochelys kempi) in the Gulf Two specimells of H. spinosa collected in the Philip- of Mexico. Final Report Nat. Mar. Fish. Serv., Southeast Fish. pines have now been identified in the collection of the Center, Panama City Lab.,7l pp. Herpetology Division, Philippines National Museum (PNM). Doon, C.K., JR. 1988. Synopsis of the biological data on the These include an adult male (Fig. 1) (identifiable from the (Linnaeus loggerhead sea turtle Caretta caretto 1758). U.S. deep plastral concavity and everted cliteropenis) and an Fish Wildl. Serv., Biol. R"p. 88(14). adult female (showing a flat plastron and a wide postanal FrsrEl,rEvER. J.R. 1918. Underwater tracking evidence of neonate gap). They were collected on Mindanao Island by ornitholo- loggerhead sea turtles seeking shelter in drifting sargassuln. gists Robert Kennedy and Pedro Gonzales. This comprises Copei a 197 8( I ): 148- 149. HrLnp,enAND,, H.H. 1983. Random notes on sea turtles in the the first record of H. spinosa for the Philippines. western Gulf of Mexico. In: Owens, D.W. et al. (Eds.). Western Measurements taken with vernier calipers to the nearest Gulf of Mexico Sea Turtle Workshop Proceedings. College 0. 1 mm of the larger adult male, PNM 2233, followed by the Station, Texas: Sea Grant, Texas A&M University, TAMU- smaller adult female, PNM 2232,and descriptions of the two sG-86-402. turtles are given below. Mnvrnru, A.B . 1982. Sea turtle rnigrations - evidence from tag Straight carapace lengths 193.6 and 179.3 mm; straight returns. In: Biorndal, K.A. (Ed.). Biology and Conservation of carapace widths 161.3 and 141.5 mm; greatest plastron Sea Turtles. Washington, DC: Smithsonian Institution Press" mm; median plastron lengths I 64.1 pp.9l-100. lengths 181.2 and Il9.l plastron lobes 85.3 and 85.3 mm; Prorrcrru, P.T. 1989. Feeding ecology of the loggerhead sea turtle and 167.0 mm; anterior in the northwestern Gulf of Mexico. M.S. Thesis, Texas A&M posterior plastron lobes 107.5 and 9l .l mm; head widths University. 31.3 and 30.4 mm; tail lengths (vent to tip) 21.4 and 27.0 PlorulN, P.T., WrcrsrEN, M.K.' AND Avtos, A.F. 1993. Feeding mm; plastral concavity depths 8.8 and 0.02 mm. Lengths of ecology of the loggerhead sea turtle Cctrettct carettct in the vertebral scutes, anterior to posteri or. 43.3, 34.9, 32.0, 32.9,, northwestern Gulf of Mexico. Mar. Biol. I l5:l -5. 35.7 and 37 .l ,33.0,30.2,30.2,33.9 mm. Lengths of plastral RrcsnnnsoN, J.1., AND McGrr-lrvARy, P. l99l . Post-hatchling log- seams, anterior to posterior: 25.7 ,12.3,39.4, 38 .3,34.0, 14.8 gerhead turtles eat insects in Sargassum community. Mar. and 18.9, 16.4,40.8,39.8, 36.8, 16.3 mm. Turtl. Newsl. 55:2-5, Shell moderately elevated, with a flattened vertebral SHnvEn, D.J. 1991. Feeding ecology of wild and head-started vertebral keel, lacking lateral keels. Kemp's ridleys sea turtles in south Texas waters. J. Herp. region. A distinct but The anterior margin of the carapace is nnserrated, the poste- 2s(3 ):327 -334. VnN NrERoR, I\4.M., AND DeN Hnnroc, J.C. 1984. A study on the rior margin weakly serrated. Nuchal small and triangular. gut contents of five juvenile loggerhead turtles, Carettct carettct Vertebral I constricted anteriorly. All vertebrals broader (Linnaeus) (Reptilia, Cheloniidae), from the south-eastern part than long, and as broad as the costals. Plastron large, the of the north Atlantic Ocean, with ernphasis on coelenterate greatest length approximately as long as the carapace, identiflcation , ZooL Meded. 59(4):35-54. emarginated anteriorly and notched posteriorly. The longest WrrHEnrNcroN, B.E. 1994. Some "lost-year" turtles found. In: median suture in the plastron is between the abdominals, the Schroeder, 8.A., and Witherington, B.E. (Compilers). Proc. shortest between the anals. Both anterior and posterior lobes Thirteenth Ann. Symp. on Sea Turtle Biology and Conserva- plastron tion. NOAA Tech. Memo. NMFS-SEFC-341,pp. 194-195.. of the plastron are llarrower than the median length, the posterior lobe wider than the bridge. Both specimens Received: 10 April 1995 . Acceptecl: l9 August 1995. have 2J annuli on costal III. Head small, upper jaw weakly