REPORT ON THE 1997 GllliEN TUllTLE PROGllAM AT TORTUGUERO, COSTA RICA Submitted to Caribbean Conservation Corporation by Sebastian Troeng Research Coordinator Caribbean Conservation Corporation 4424 NW 13th St. Suite A-I Gainesville, FL 32609 Ph: (352)373-6441 Fu: (352) 375-2449 Email: <[email protected]> Homepage: <http://www.cccturtle.org> TABLE OF CONTENTS 3.3Tagging 12 3.3.1Effort 12 3,3.2 Turtle encounter efficiency 12 TABLE OF CONTENTS 3.3.3 Tag Application and Data Collection 12 3.3.4 Tag Loss 15 LIST OF FIGURES iii 3.3.5 Biometric Data Collection 16 3.3.6 Precision of Measuremellls 19 LIST OF TABLES iii 3.4 Dead Turtles 19 3.5 Environmental Awareness Activities 19 ACKNOWLEDGEMENTS iv 4. DISCUSSION 20 I. INTRODUCTION 4.1 Preparations 20 4.2 Track Surveys 21 2. METHODS 1 4.2, I 18-mile Track Surveys 21 1 2.1 Preparations 4.2.2 Track Surveysfrom Boca del Rio Tortuguero to Mile 5 Marker 21 1 2.2 Track Surveys 4.2.3 Track Surveys North of Boca del Rio Tortuguero and South of Boca del Rio 2] 2.2.1 18-mile TrackSurveys 1 Parismina 2 2.2.2 TrackSurveysfrom Boca del Rio TortuguerotoMile 5 Marker 4.2,4 Seasonal Distribution of Nesting Activity 21 2 2.2.3 TrackSurveys North of Boca del Rio Tortugueroand South of Boca del Rio 4.2.5 Spatial Distribution of Nesting Activity 21 Parismina 4.2.6 J/Jegal Harvest 22 2 2.2.4 Seasonal Distribution of Nesting Activity 4.3Tagging 23 2 2.2.5 Spatial Distribution of Nesting Activity 4.3.I Effort 23 2 2.2.6 J/Jegal Harvest 4,3,2 Turtle encoulller efficiency 23 2 2.3 Tagging 4.3.3 Tag Application and Data Collection 23 2 2.3.1 Effort 4,3,4 Tag Loss 24 3 2.3.2 Turtle encoulller efficiency 4.3.5 Biometric Data Collection 24 3 2.3.3 TagApplication and Data Collection 4.3,6 Precision of Measurements 25 4 2.3.4 TagLoss 4.4 Dead Turtles 25 2.3.5 Biometric Data Collection 4 4.5 Environmental Awareness Activities 25 2.3.6 Precision of MeasuremenlS 5 2.4 Dead Turtles 5 s. REFERENCES 26 2.5 Environmental Awareness Activities 5 6. RECOMMENDATIONS 27 3. RESULTS 5 6.1 Preparations 27 5 3.1 Preparations 6.2 Track Surveys 27 5 3.2 Track Surveys 6.3 Tagging 27 5 3.2.1 18-mile TrackSurveys 6.4 Dead Turtles 28 5 3.2.2 TrackSurveysfrom Boca del Rio Tortugueroto Mile 5 Marker 6.5 Environmental Awareness Activities 28 3.2.3 TrackSurveys North of Boca del Rio Tortugueroand South of Boca del Rio 6 Parismina APPENDICES 3.2.4 Seasonal Distribution of Nesting Activity 6 3,2.5 Spatial Distribution of Nesting Activity 6 3.2.6 J/Jegal Harvest 6 " LIST OF FIGURES ACKNOWLEDGEMENTS Figure I. Seasonal distribution of green turtle nestingactivityITommile3 marker to mile 7 17 marker as determined ITomtrack surveys(n-30). The 1997 Green Tunle Program was made possible by the cumulative effons of a group of dedicated people. A grand thanks is due all those tbat contributed to making the program a Figure 2. Seasonal distribution of green tunle encounters ITom Boca del Rio Tonuguero 8 success. to mile 5 marker (n=2,416). The Ministry of Environment and Energy (EI Ministerio del Ambiente y Energia) issued the Figure 3. Spatial distribution of nesting activity ITom 5 miles nortb of Boca del Rio 9 researcb permit for tbe 1997 Green Turtle Program (Resolucion No. 137-97-0FAU). Tortuguero to 5 miles soutb of Boca del Rio Parismina as determined ITom track surveys (6 July-26 September). All data presented in this report were collected by the enthusiastic and hardworking research assistants, with support ITom program participants (Appendix I). Their long hours of work Figure 4. Spatial distribution of green turtle nests and false crawls fi'om Boca del Rio 10 and higb quality performance are gratefully acknowledged. Tortuguero to the mile 5 marker (12 track surveys, 8 July-I 8 September). Freddy Piedra Pocbel, CCC station manager, and Grethel Monge, tbe visitor centre Figure 5. megal harvest of green turtles ITom the nesting beach as determined ITom track II administradora, efficiently organized the logistics of the program in Tortuguero. The surveys (6 July-26 September): a) Boca del Rio Tortuguero to mile 5 marker, b) Mile 5 boatdriving, day and night, by Enrique Martinez and Carlos Ortega, and tbe cooking of marker to Laguna Jalov&, and c) Boca del Rio Parismina to S miles south of Boca del delicious food by Zelmira BenJys-Williams and Gloria BenJys, throughout the season, were Rio Parismina. much appreciated. Figure 6. Spatial distribution of nesting activity ITom 5 miles north of Boca del Rio 13 The villagers ofTortuguero contributed in many ways to the program and their hospitality Tonuguero to 5 miles soutb of Boca del Rio Parismina as determined ITom track was encouraging. I would especially like to thank Thomas Alonso Rankin Gonzalez for surveys: a) 6 July-26 August, and b) 27 August-26 September. conducting the 18-mile track surveys, for solving problems and for stimulating turtle discussions. Many thanks to Carlos Olivas, the students of Tortuguero school, and the Figure 7. Ratio (RIll) between tbe proportion of green turtle encounters and tbe 14 ecological group T.A.A.F.F., for mucb fun. Their enthusiasm gives great hope for the future proportion of nesting activity (in section) p~ 1/8 mile. ofTortuguero. The tourguides ofTonuguero and tbe tourist lodges contributed with information on tagged turtles, and with criticism throughout the program. Their assistance Figure 8. Green tunle lengtb-frequency distribution (SCLmax): a) remigrants (n=23), 17 was constructive and useful. and b) recruits (n=135). Roxana Silman and Raill Gomez Gonzalez at the CCC office in San Jose, and David Godfrey Figure 9. Green tunle clutch size-ITequency distribution: a) remigrants (n=22), and b) 18 and Lucinda Taft at tbe CCC office in Gainesville provided support whenever needed. Cathi recruits (n=131). Campbell provided initial training and thorough guidance to the RC and the RAs. Cynthia Lagueux provided guidance on the finer points of the research protocol. LIST OF TABLES The staff of Tonuguero National Park (ACTo) responded quickly to our various requests, in Table 1. Illegal harvest of green turtles from tbe nesting beach. 6 particular with regards to security on tbe beacb. The green turtle population of T ortuguero will benefit greatly ITom continued and expanded cooperation between CCC and ACTo. Table 2. Tunle encounter efficiency (%). 12 Dr. Anne Meylan and Seilora Elvira Carrillo kindly provided information on the origin of long Table 3. Within-season tag loss, first-to-Iast encounter: a) by RA present at the time of 16 distance tag recoveries. tagging, and b) by montb of tagging. Dr. Karen Bjomdai, Dr. Alan Bolten, Cynthia Lagueux and Dr. Anne Meylan provided many Table 4. Biometric data. 19 useful comments on the draft report. Table 5. Precision of measurements. 19 iii IV I. INTRODUcnON 2.2.2 Track Surveysfrom Boca del Rio Tortugucro to Mile 5 Marker Track surveys were conducted weekly ITom Boca del Rio Tortuguero to the mile 5 marker. Green turtle (Chelollia mydas) tagging and monitoring in Tonuguero was initiated in 1955 These track surveys were always conducted by the RC, sometimes accompanied by RAs or participants. The track surveys began at Sam at Boca del Rio Tortuguero, and finished at the (CarT et 01. 1978) and has since been conducted every nesting season. The 1997 Green Turtle mile 5 marker at 8am (with the exception of29 July when the track survey did not end until Program extended from I July to 20 September. The program was organised by the Caribbean 12am due to high nesting activity the previous night). The number of nests and false crawls Conservation Corporation (CCC) and implemented by a group of research assistants (RAs) from the previous night only were recorded for each 1/8 mile section. Tracks were recorded and panicipants headed by the research coordinator (RC). The objectivesof the 1997 Green separately for each species. Evidence of illegal harvest of turtles or eggs, such as the dragmark Turtle Program were: a) to quantiJy the nesting activity along the Tortuguero nesting beach of a flipped-over turtle. dug up nests, and stick probing marks around nests, were also with emphasis on the section ITom Boca del Rio Tonuguero to the mile 5 marker, b) to recorded. quantifY biometric parameters of the nesting green turtle population such as carapace length and clutch size. c) to quantifY the level of illegal harvest of green turtles and eggs ITom the 2.2.3 Track Surveys North of Boca del Rio TortuJ:llero and South of Boca del Rio nesting beach, and d) to promote environmental awareness, in order to further local Parismino understanding of and support for, the conservation of the Tonuguero marine turtle Track surveys were conducted, a total of three times, for 5 miles of beach north of Boca del populations. Rio Tortuguero and for 5 miles of beach south of Boca del Rio Parismina. These track 2. METHODS surveys were conducted by teams of three RAs. The number ofnests and false crawls from the previous night only were recorded. Tracks were recorded separately for each species. Evidence of illegal harvest of turtles or eggs, was also recorded. 2.1 Preparations Prior to the start of the program, the positions of the mile markers from Boca del Rio 2.2.4 Seasonal Distribution of Nestillg Activity Tortuguero to the mile 5 marker were checked by RAs using a 3OO-foot fiberglass measuring Seasonal distribution of nesting activity was determined from the results of the I S-mile track tape.