THE ECOLOGY AND MIGRATIONS OF SEA TURTLES, 7. THE WEST CARIBBEAN GREEN TURTLE COLONY ARCHIE CARR, MARJORIE HARRIS CARR, AND ANNE BARKAU MEYLAN BULLETIN OF THE AMERICAN MUSEUM OF NATURAL HISTORY VOLUME 162 : ARTICLE 1 NEW YORK : 1978 S1~~~~~~~~~~~~~~~~~~~~~~~~ 4~~~~~~4 I 4 ~~~~~ O ~~~~~~~~j~~~~~~~44'4j~~~~~~~~~~~~~~~~~~~~~~4.4~H4r4q47;'k~~~~~~~~47~~~~~4'~~ ~~~~~~~Zi~ ~ ~ p474 ~~~~~~~ 4q -'~~~14'4' ~~~~S4 '44,I~~~~' ~~~'4 444 P 4 _e_'7' 4.444 '444'44*~~ ~ '~y~i'~~'4~ ~ '4445 47 "4 4~~47'44774 4r727 544-1;3;*~* >-t j "444'4Z,IP 4~4 "4*~~~~~~~i~~~2" s4-4~44 " '44 4~ "A'A '4~~~~~~~i4744z47f q '' { , 4447 "44~~~~~~~~~~~~~~'445~~ ~ ~ ~ ~ ~ ~ b3"4 44 .$44. 4 t Xi~~~~~~~~'4,4{4 *4 444 ' '4', 04½i'~~~44' 444444 4 4744 4V~~~~~~~~~~~~~~~~~~~~~~'i~Z4~~~A" 4 A'7'~ 7 4 ~ 4444,44444454.74,n 74.'44. 4''4" "'44i44t4441p4;4'4:''V W ''44~~44~4 ~~4444'~~~#,'4~~ '4474 ~ ~ ,44'44'44444~~~4#~47~~74474447'4S 4- 4" 4 ~ >" ,f444754441~ 4444447 "4~4"t' 444~7444444''"4 ~74 4 .4744744~~~',4744~4! 7~44447477'474474,~4k4 474A44:y4'4g 4' 444744444"~.444'' " 4"" fk 'r P4',~~~ ~ ~ ~ ~ ~ ~ ~ 4'~.4 444, 474 44. 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THE WEST CARIBBEAN GREEN TURTLE COLONY ARCHIE CARR Research Associate, Department of Herpetology The American Museum of Natural History Graduate Research Professor, Department of Zoology University of Florida MARJORIE HARRIS CARR President, Florida Defenders of the Environment Gainesville, Florida ANNE BARKAU MEYLAN Department of Zoology University of Florida BULLETIN OF THE AMERICAN MUSEUM OF NATURAL HISTORY VOLUME 162 : ARTICLE 1 NEW YORK: 1978 BULLETIN OF THE AMERICAN MUSEUM OF NATURAL HISTORY Volume 162, article 1, pages 1-46, figures 1-19, tables 1-13 Issued December 4, 1978 Price: $2.90 a copy ISSN 0003-0090 Copyright © The American Museum of Natural History 1978 CONTENTS Abstract. .................... 5 Introduction . ...................S5 Background and Early Results ............ ........5 The Tagging Technique. .................... 10 The Region ...................... ................... 10 Acknowledgments. ............... ...... 15 Migration-The International Tag Recoveries ...... .................. ... 16 Nesting and Renesting .................. .................. ... 22 Remigration. .................. ... 28 Reproductive Homing .................. .................. ... 35 Size of the West Caribbean Population ......... .................. ... 37 Applications of the Research and Outlook for the Future .................. 42 Literature Cited ..................... .................. ... 43 ABSTRACT The present report is a summary and preliminary (3) Remigration: Of 1412 turtles that have re- analysis of data on the green turtle, Chelonia mydas, turned to Tortuguero after previous appearances that has been collected during a 22-year tagging there, only six came back the following season. program at Tortuguero, Costa Rica, 52 miles north Interval percentages for the three predominant re- of the Caribbean city of Puerto Limon. It is the first migration periods are: two years, 21 percent; three general account of Tortuguero results since 1960. years, 49 percent; four years, 18 percent. A unique From 1955 through the 1976 season, approximately contribution of the report is an extensive record of 12,000 female green turtles have been tagged on the remigratory cycle-shifts, and tables showing com- nesting beach. Of these, 2522 have been seen in position of the nesting colonies of 1962-1972 with subsequent years; 1412 of them as return migrants respect to past and future remigration-interval fre- and 1110 on distant forage grounds or in migration. quencies. No turtle tagged at Tortuguero has ever been re- (4) Reproductive homing: A distinction is made ported from any other nesting shore. between philopatry, or regional retum, and site fix- The paper is concerned mainly with the migratory ity-the tendency to nest repeatedly on the same and behavioral ecology of the colony and with inter- beach section within the home region. These two seasonal changes in the nesting population. Results surely involve different cues; and the responses me- are presented in five sections, as follows: diating open-sea orientation must be different from (1) Migratory geography and speed of travel: Of both. 1110 long-distance, postseasonal recoveries of Tor- (5) Size of the West Caribbean population: A tuguero tags 957 have come from the Miskito Cays calculation of the number of sexually mature green and adjacent parts of Miskito Bank off the Nic- turtles in the western Caribbean is made. An equa- araguan coast. Smaller numbers of recoveries cluster tion that takes into consideration the different pro- in Colombia, Panama, and Mexico. Analysis of portions of two-, three-, and four-year remigratory monthly recovery frequencies in Nicaragua, and of periods is used to convert nesting arrivals into total periods of time elapsed between tagging and recap- female population. Since the latter varies from year ture, reinforce the assumption that Miskito Bank is a to year, the average for the last six years is used in resident foraging range and not merely a travel sta- the calculation, and the resulting figure is doubled, tion. Migratory travel speeds based on tag recoveries on the assumption that there is a 1:1 sex ratio. The are compared with those recorded in the literature. resulting total of mature green turtles in the popula- (2) Nesting and renesting: The average number of tion is 62,532. nestings by a Tortuguero turtle during a season at the In the final section, the future outlook for the breeding shore is 2.8; the recorded maximum is population is assessed and the need for further re- seven, although eight probably occur occasionally. search in its shifting habitats, particularly the inter- There is evidence that one-time nestings are a regu- nesting habitat, is pointed out. The critical im- lar occurrence. The average renesting interval is 12.1 portance of developing an excluder device to keep days. Remigrant turtles were found to nest more sea turtles out of shrimp trawls is discussed. often than recruits. INTRODUCTION The chief aim of the research has been to fill BACKGROUND AND EARLY RESULTS some of the remaining gaps in the life cycle of one species, the green turtle, Chelonia mydas, The life cycles of the five genera of sea with special reference to the population of the turtles are fundamentally similar. Figure 2 is a western Caribbean Sea (fig. 1). The research diagram of the developmental and seasonal program began in 1955 at Tortuguero, on the changes that occur in the ecology of Chelonia. Caribbean coast of Costa Rica, and has been With minor modifications, especially those re- resumed each season since that year. garding the adult foraging habitat, the diagram 5 NF. -______ Al"0.7 FIG. 1. Two views of a Tortuguero green turtle on the beach. A. Frontal view, showing the low transverse silhouette and shallow nuchal arch. B. Side view of the same turtle. 1978 CARR, CARR AND MEYLAN: GREEN TURTLE COLONY 7 is also applicable to the life cycles of the other distance travel, often across open ocean, be- genera. Feeding and mating take place in the tween circumscribed, racial breeding and feed- water, eggs are laid on shore, and copulation ing grounds. occurs mainly at the nesting ground. There is When sea turtle research was first under- growing evidence that all sea turtles are to taken at the University of Florida 22 years ago, some degree migratory. Tag recoveries indicate Chelonia was the only marine turtle of which that the leatherback, Dermochelys, may travel the reproductive ecology had received substan- farther away from the rookery than any other tial attention in the western Pacific. Primarily species (Pritchard, 1971, 1976), and circumstan- because of its economic importance-especially tial evidence supports this. However, log- that of the eggs in the diet of various seaside gerheads and ridleys likewise travel, or wander, Moslem peoples-British colonial governments through extensive foraging habitat. The her- had encouraged investigations of green turtle bivorous green turtle appears to be the only one nesting colonies, and some of these (Moor- in which the migrations involve periodic long- house, 1933; Banks, 1937) made significant, though fragmentary, contributions to the natural history of Chelonia. Extensive studies in Ceylon were summarized by P. E. P. De- raniyagala (1939). In Borneo, Tom Harrisson (1951, 1954, 1956) renewed an investigation that had been begun earlier by Banks (1937) in the Turtle Islands of Sarawak and set up a program of tagging and management there. John R. Hendrickson, then of the University of Malaya, continued studies of the Sarawak nest- ing colonies, and his results appeared in a valu- able paper in 1958. Publications involving Atlantic sea turtles were, until recently, restricted to a few regional lists, descriptive accounts, and fisheries reports (Garman, 1880, 1888; Hornell, 1927; Cadenat, 1954). Loveridge and Williams (1957) and Vil- liers (1958) summarized the known distribution of the West African species. Lewis (1940) de- scribed changes brought about by man in Car- ibbean green turtle populations; and Ingle and Smith (1949) compiled literature on the Atlantic green turtle and turtle industry in a work later revised and expanded by Rebel (1974). In his NESTING BEACH history of the economic role of Chelonia, Par- FIG. 2. Seasonal and ontogenetic changes in the sons (1962) contributed a helpful reconstruction ecologic geography and habitat of Chelonia. The of the primitive zoogeography of the genus. "lost year"-actually a period from seven to about In an FAO monograph published in 1971, 14 months in duration-is almost certainly passed in Harold Hirth summarized world literature on a pelagic habitat, probably drifting sea weeds. On the green turtle through 1970. That paper, reappearing the juveniles turn up in various inshore along with books on sea turtles for the general estuarine or reef-system habitats, often on a regular schedule of arrival and departure times.