“CONSERVATION OF LEATHERBACK TURTLES IN THE MEXICAN … · 2020. 1. 21. · Conservation of leatherbacks in Mexico Season 08-09 1 BACKGROUND The leatherback turtle (Dermochelys

“CONSERVATION OF LEATHERBACK TURTLES IN THE MEXICAN PACIFIC”

FINAL TECHNICAL REPORT

EXECUTIVE SUMMARY FOR NESTING SEASON 2008-2009 Submitted by Kutzari, Asociacion para el Estudio y Conservación de

las Tortugas Marinas AC

To National Fish and Wildlife Foundation in compliance with Grant Agreement # 2008-0064-006

The views and conclusions contained in this document are those of the authors and should not be interpreted as representing the opinions or policies of the National Fish and Wildlife Foundation. Mention of trade names or commercial products does not

constitute their endorsement by the National Fish and Wildlife Foundation.

General Coordination Proyecto Laúd: Laura Sarti

Programa Nacional para la Conservación de las Tortugas Marinas, CONANP

Report compilation and information analysis:

Ana Rebeca Barragán Programa Nacional para la Conservación de las Tortugas Marinas, CONANP

Marlem Zenteno Kutzari, Asociación para el Estudio y Conservación de las Tortugas Marinas, A.C.

Administration: Patricia Solís Kutzari, Asociación para el Estudio y Conservación de las Tortugas Marinas, A.C.

Field work was performed by: Mexiquillo: Gustavo Hernández Molina1, Jorge Carlos Salas Jiménez2, José Raymundo Gil López2, Verónica

Vega2, Comité para la protección a las tortugas marinas “El Salado” y Comité para la protección a las tortugas marinas “La Manzanilla II”

Tierra Colorada: Enrique Ocampo Olvera3, Víctor Manuel Vargas Ortega3, Guadalupe Chávez2, Crisóforo Noyola Bernal6, Felipe Bernal Campos6, Oscar González6

Cahuitán: Marlem Zenteno2, Mario Astorga2, Amaranta Ramirez2, Ronald Echeverria2 y Comité de Protección Comunitario de Cahuitán

Barra de la Cruz: Alejandro Tavera Rivera4, Quiauxóchitl Inés Gómez Padrón2 y Comité de Protección Comunitario de Playa Grande

Volunteers Adriana Angulo, María del Rosario Juárez Hernández, Areli Alejandra Muñoz Cervantes 1 Dirección Regional Occidente y Pacífico Centro, CONANP 2 Kutzari Asociación para el Estudio y Conservación de las Tortugas Marinas, A.C. 3 Dirección Regional Frontera Sur, Istmo y Pacífico Sur, CONANP 4 Centro Mexicano de la Tortuga, CONANP. 5 Dirección de Especies Prioritarias para la Conservación CONANP. 6 Community participants from the “Temporal Employment Program”. This report should be cited: Barragán, A., M. Zenteno and L. Sarti. 2010. Conservation of leatherback turtles in the Mexican Pacific. Executive Summary for nesting season 2008-2009. Final Technical Report. Kutzari AC / Programa Nacional para la Conservación de las Tortugas Marinas, CONANP. 10 pp



TABLE OF CONTENTS BACKGROUND............................................................................................................................................... 1 METHODS ....................................................................................................................................................... 4 RESULTS.......................................................................................................................................................... 5

A) MONITORING ACTIVITIES, IDENTIFICATION OF FEMALES AND POPULATION ESTIMATE ............................... 5 B) PROTECTION ACTIVITIES ............................................................................................................................ 6 C) OTHER SEA TURTLE SPECIES....................................................................................................................... 7 D) MORTALITY AND STRANDINGS .................................................................................................................. 7

DISCUSSION ................................................................................................................................................... 8 LITERATURE CITED.................................................................................................................................... 9



Conservation of leatherbacks in Mexico Season 08-09

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BACKGROUND The leatherback turtle (Dermochelys coriacea) is the largest of all living sea turtles. It has been considered an endangered species worldwide since the early 80’s and it was recently listed as Critically Endangered in IUCN Red List (Sarti, 2000). René Márquez wrote the first report of leatherbacks nesting in the Mexican Pacific in 1976, and mentioned that the beach of San Juan Chacahua in Oaxaca (15° 57’N 97° 41’W - 15° 56’N 97° 33’W) was the most important nesting site in Mexico, with 2,000 females nesting each season. He also listed Maruata, Colola (Michoacán), Piedra de Tlacoyunque (Guerrero) and Escobilla (Oaxaca) as important nesting beaches for the leatherback. In 1981, Márquez referred to Tierra Colorada (Guerrero) and Mexiquillo (Michoacán) as major nesting sites for this species, calculating around 3,000 to 5,000 females nesting per season in each of these beaches (Márquez et al., 1981). Pritchard conducted the first aerial survey along the Pacific coast of Mexico in 1981, which allowed him to estimate the size of the leatherback nesting population in the region (Pritchard, 1982). As he admits, it was impossible to directly count the nests due to the high density; nevertheless estimations suggested that the area between Maruata (18° 15’30”N 103° 05’23”W) and the Tehuantepec Isthmus (16°10’N 95°00’W) hosted a nesting population of 75,000 females. He concluded that this was the largest leatherback nesting population in the world, which represented 65.2% of the global estimate of 115,000 females. Pritchard also observed remains of dead females on some beaches, which indicated that illegal slaughtering was common. Pritchard’s aerial survey and population estimate for the Mexican Pacific leatherbacks, done in 1981, was the only study of its kind up to 1995. For more than a decade the only information available were local unpublished data for certain areas and certain years, gathered by independent working groups from Mexiquillo, Tierra Colorada, Barra de la Cruz and San Juan Chacahua. North of the country, Márquez provided some isolated information about leatherbacks nesting in Todos Santos, Baja California (Márquez and Carrasco, 1993). The beach of Mexiquillo has the oldest uninterrupted conservation program for the leatherback in Mexico, which has generated over two decades of biological information for this species. During this period the researchers from the National University of Mexico (UNAM) documented annual fluctuations in the number of leatherback nests, recording from 3,000 to 5,000 nests per year from 1982 to 1989. In the 1993-1994 nesting season the first sharp decline in the number of nests recorded in Mexiquillo caused great concern (Fig. 1). Although conservation projects in other Pacific beaches like Tierra Colorada, Chacahua and Barra de la Cruz were either younger or not continuous, the same sharp decline in nesting numbers was noticed in the 1993-1994 season. Sarti et al. (1994) suggested that this decline in the nesting numbers could be attributed to: a) a true decrease in the number of leatherbacks in the Mexican population, due to intensive egg harvest and killing of adult females both on beaches and in open waters, b) natural fluctuations of the reproductive biology of this species, c) movement of the females to other nesting areas.




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Historical abundance of leatherback nests in the Mexican Pacific

Chacahua Barra de la Cruz Tierra Colorada Cahuitán Mexiquillo

Figure 1. Recorded decline of leatherback turtle nestings at index beaches of the Mexican Pacific (Sarti et al., 2007). The concern caused by the low leatherback nesting numbers in 1993-1994 motivated several researchers from different institutions to join forces and in 1995 a new coordinated conservation effort took shape as “Proyecto Laúd” (Leatherback Project). Proyecto Laúd identified the major nesting sites as index beaches used for evaluating the population size: Mexiquillo, Tierra Colorada, Cahuitán and Barra de la Cruz. Proyecto Laúd, currently under the auspice of CONANP (National Commission for Natural Protected Areas), compiles the data generated by government and non-government institutions working at important leatherback beaches in a single database. The project also standardizes the field methods throughout the nesting range and monitors the fluctuations of the leatherback nesting numbers in the Mexican Pacific. The ongoing monitoring efforts of Proyecto Laúd have shown that the Mexican Pacific leatherback population continues to decline, although the trend is not as steep as in the early 90’s (Fig. 2). This situation grants for the continuation of full protection efforts in the major nesting beaches of the Mexican Pacific.




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Barra de la Cruz, Oax. Tierra Colorada, Gro. Cahuitán, Oax. Mexiquillo, Mich.

Figure 2. Leatherback nesting trend for the last decade at index beaches of the Mexican Pacific (Proyecto Laúd, unpublished information). The objectives of the project during 2008-2009 nesting season were:

1. To estimate the nesting population size of the leatherback turtle along the Mexican pacific during 2008-2009 nesting season

2. To protect at least 90% of the total number of clutches laid in the four index beaches (Fig. 3).

3. To have al least 50% of hatching success, recruiting healthy hatchlings to the population

4. To promote the participation of members of the local communities in protection activities.




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Figure 3. Distribution range of the leatherback turtle in the Mexican Pacific (Sarti et al., 2007).

METHODS In order to accomplish these objectives, teams of field technicians worked at the index beaches for the full nesting season (October 2008 to May 2009). The teams patrolled the beaches each night from 20:00 to 05:00 hrs, looking for nesting females. All the females were checked for tags. Previously untagged females were equipped with two kinds of tags: one metal tag (Monel or Inconel) placed in the right hind flipper and one PIT (Passive Integrated Transponder, AVID brand) injected in the right shoulder, using standard procedures (Balazs, 2000). Notes were made on the presence of old tag scars, pink spot, epifauna and general body condition. The standard curve carapace length (CCL) and width (CCW) were obtained from each female with a plastic measuring tape. If the female built a nest and didn’t lay eggs, that activity was annotated as “failed oviposition”; the presence of a clutch could only be verified by direct observation of the laying process or direct evidence of it (e.g. eggs, egg shells). The number of nesting emergences per night was verified with an early morning track count over the whole length of each beach, in case some of such events weren’t encountered during the night. Difference was made between nests (tracks with a bodypit) and non-nesting emergences (tracks without a bodypit). Other observations were made during the track counts, such as dead turtles, predated or poached nests or nests lost to natural attrition.




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Since poaching and predation conditions in all the index beaches make in situ incubation unsafe, the clutches were collected as they were laid and relocated to protected fenced areas as soon as possible, usually within 1-2 hours. The hatchlings were released upon emergence, in different areas of the beach each time, in order to avoid predator concentrations. After hatchling emergence, the nests were opened and all contents were excavated to evaluate hatch success (%H = egg shells / number of eggs). Recruitment was evaluated as total number of released hatchlings/number of eggs.

RESULTS

a) Monitoring activities, identification of females and population estimate The field activities started on late October and ended in mid-May, the exact date varied among index beaches. Because of safety concerns, in Mexiquillo the team only did two patrols per night throughout the nesting season, scheduled around the high tide and trying not to relocate the clutches past 4 – 5 hrs after lay. The rest of the beaches patrolled using standard procedures. The beach with the largest number of leatherback nests was Tierra Colorada. The results of number of nestings, oviposition success and estimated number of clutches are shown in Table 1.

Mexiquillo Tierra Colorada Cahuitán Barra de la Cruz

Total Index Beaches

Total number of Nests 69 192 42 110 413 Observed nestings 52 170 39 106 367 Confirmed clutches 46 154 38 100 338 Oviposition Success 88.5% 90.6% 97.4% 94.3% 92.1% Total Estimated Clutches 61 174 41 104 380

Table 1. Results of monitoring activities in four index beaches of the Mexican Pacific during leatherback season 2008-2009 From the tagging activities, we identified 85 leatherback females nesting in the four index beaches, from which a large part were neophytes and for 11 there was no confirmation of presence of old tags or tags scars (mostly from Mexiquillo), as shown in Table 2. The average clutch frequency was 6.7, and the average clutch interval was 10.4 days.

Females Mexiquillo Tierra Colorada Cahuitán Barra de la

Cruz Total Index

Beaches Neophytes 0 18 9 23 50 Remigrants 2 12 1 9 24 Unknown 7 3 0 1 11 Total 9 33 10 33 85

Table 2. Results of tagging activities in four index beaches of the Mexican Pacific during leatherback season 2008-2009




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Proyecto Laúd has been consistently doing saturation tagging of leatherback females with two kinds of tags since 1996 in the four index beaches. After this time, it is most likely that the females found without tags or signs of prior tagging are true neophytes; the large proportion of neophytes identified during this nesting season (more than 50%) is encouraging given the depleted condition of the population. If the index beaches held 45% of the total nesting in the Mexican Pacific (Sarti et al., 2007), we estimate that about 846 clutches were laid by 126 females in the whole coast (considering 92.1% total oviposition success and a clutch frequency of 6.7). We emphasize that this is a gross estimate which does not consider the distribution details and error corrections that would come from aerial survey data.

b) Protection activities The field teams protected about 85% of the leatherback clutches estimated in the four index beaches (Table 3). Although the goal of protecting 90% globally couldn’t be reached, two of the nesting beaches protected a higher percentage.

Mexiquillo Tierra Colorada Cahuitán Barra de

la Cruz

Total Index

Beaches Total nests in season 69 192 42 110 413 Total estimated clutches 61 174 41 104 380 Protected clutches 43 148 38 95 321 Protected eggs 2,724 9,967 2,320 6,533 21,544 Released hatchlings 1,162 5,610 1,174 3,088 11,034 % protection full season 70.5% 85.1% 92.7% 91.3% 84.9% % avg hatching success (E1) 46.5% 57.3% 50.5% 46.1% 50.1% % hatchlings released 46.7% 57.1% 49.3% 46.1% 49.8%

Table 3. Results of protection activities in four index beaches of the Mexican Pacific during leatherback season 2008-2009 Mexiquillo had security concerns related to past assaults and drug traffic in the region; the fact that the teams couldn’t patrol the beach consistently all night long contributed to the low protection rate reported. In the case of Tierra Colorada, the length (26 km) and the dynamics of the beach, in which some areas are covered by the high tide in certain months, difficult the patrolling. All index beaches had surveillance from PROFEPA (Federal Environmental Protection Enforcement Agency) and the Mexican Navy, which greatly contributed to the reduction of poaching in the patrolled areas. Also, the field teams worked in close collaboration with the local communities, which formed Protection Committees for assisting the project in the collection of clutches and protection of females. The members of these local protection committees received training in management techniques and were constantly assisted by the field staff.




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c) Other sea turtle species All the index beaches have olive ridleys (Lepidochelys olivacea) and Pacific green turtles (Chelonia mydas) nesting during the leatherback season. These clutches were also protected; the results are shown in Table 4. L. olivacea C. mydas

Total

Estimated Clutches

Protected Clutches

Protected Eggs

Hatchlings Released

Total Estimated Clutches

Protected Clutches

Protected Eggs

Hatchlings Released

Mexiquillo 1,040 1,286 112,591 76,347 58 44 2,763 1,915 Tierra Colorada 571 437 40,476 31,462 6 6 374 331 Cahuitán 931 709 65,637 54,261 37 29 1,779 1,436 Barra de la Cruz 424 244 23,119 19,320 21 18 1,280 1,113 Total 2,966 2,676 241,823 181,390 122 97 6,196 4,795

Table 4. Results of protection activities for the other sea turtle species nesting in four index beaches of the Mexican Pacific during season 2008-2009

d) Mortality and Strandings No leatherbacks were reported dead in any of the index beaches. Observations of stranded carcasses or other kinds of mortality were done for the other species during the patrols and daily track counts, which are summarized in Table 5.

Female Male Unknown Total L. olivacea 12 2 2 16

E. imbricata 0 0 1 1 Mexiquillo C. mydas 1 0 7 8

L. olivacea 6 3 3 12 E. imbricata 0 1 1 2 Tierra Colorada

C. mydas 2 0 0 2 L. olivacea 18 1 1 20

E. imbricata 0 0 0 0 Cahuitán C. mydas 1 0 1 2

L. olivacea 11 2 4 17 E. imbricata 1 0 0 1 Barra de la Cruz

C. mydas 3 2 1 6 L. olivacea 47 8 6 61

E. imbricata 1 1 2 4 TOTAL C. mydas 7 2 8 17

Table 5. Results of mortality observations for the other sea turtle species at four index beaches of the Mexican Pacific during season 2008-2009 The causes of mortality varied among index beaches. In Mexiquillo most of the remains were from turtles slaughtered by poachers for eggs or meat; in Tierra Colorada the turtles were long dead before stranding on the beach, with signs of interaction with fishing gear, and fishing boats were reported very close to the beach. In Cahuitán the major cause of




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mortality was predation of nesting females by dogs, and in Barra de la Cruz all the remains were from turtles with signs of interaction with fishing gear, like marks of monophylament lines or propeller strikes on the carapace. Historic records of Pacific hawksbill (Eretmochelys imbricata) nesting in the project’s index beaches are extremely scarce; only 3 in 20 years. Nevertheless, carcasses of juvenile or adult hawksbills appear stranded in those beaches every year. It is possible that in the vicinity of the leatherback beaches are areas that might be of importance to the Pacific hawksbill, another critically endangered population, which we don’t know about.

DISCUSSION The socioeconomic and logistic conditions of the major leatherback nesting beaches in the Mexican Pacific still don’t allow to have 100% nest protection; nevertheless, important advances are being made on this respect. This season we protected 85% of the leatherback clutches in the index beaches, which is among the highest global protection rate obtained by the project to date. It is vital to keep ensuring the participation of the law enforcement government agencies (Profepa and Secretaria de Marina), which are the ones entitled to prosecute environmental offenders. It is also of major importance to involve a larger number of community members in conservation activities, not only for the turtles themselves but for their critical habitat; the local communities are just starting to understand the need to protect the nesting beach and the ocean in front of it, not only the leatherbacks as individuals, but there is still a great need of education in the areas adjacent to the nesting beaches. The nesting population of leatherbacks in Mexico is not recovering in spite of more than a decade of coordinated protection efforts. As shown in Figure 3, the trend in the number of nests recorded at the index beaches seems to be stabilizing for the last few years, but is still declining. Also, there are large fluctuations over the years, which are common in depleted populations. We consider that the large proportion of neophytes recorded during this nesting season is a product of the early conservation efforts done in some of the beaches, but we don’t have information on the survival rates of each life stage for this population. Mortality at sea for the Mexican Pacific leatherback hasn’t been accurately described, and there is a great need for this information. Mexico is taking the first steps towards this evaluation and the reduction of threats at sea, with some awareness workshops with fishers in the Pacific and discussion forums including fisheries authorities and researchers. We expect that the protection measures for females, eggs and hatchlings at the index beaches, with proper management techniques to avoid biases in sex ratios or health problems for hatchlings, will increase the recruitment of this population in a way that will revert the declining trend after 15 to 20 years of the beginning of the activities of Proyecto Laud in 1997. More than a decade away from this start, there is clearly a long way to go before these expectations are met, although some encouraging signs are seen. One of the most significant advances has been the incorporation of a larger number of community




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organizations to the conservation efforts for the leatherback turtle. It is clear that the awareness of the local people is greater now than at the start of the project, and many communities express concern for the decline of the population and are willing to collaborate. The conservation of the Mexican Pacific leatherback is a long-time endeavor and commitment for the organizations part of Proyecto Laúd. For now, the best strategy is an integral one, with full protection at the major nesting beaches, and research to detect and reduce threats at sea.

LITERATURE CITED 1. Balazs, G. 1999. Factors to consider in the tagging of sea turtles. In: Eckert, K., Bjorndal,

K., Abreu-Grobois, A. and Donnelly, M. (Eds.) Research and management techniques for the conservation of sea turtles. IUCN/SSC Marine Turtle Specialist Group Publication No. 4. 101-109

2. Márquez, R. 1976. Reservas naturales para la conservación de las tortugas marinas de México. Instituto Nacional de la Pesca. INP/SI:i83, 22 pp.

3. Márquez, R., Villanueva, A., and Peñaflores, C. 1981. Anidación de la tortuga laúd Dermochelys coriacea schlegelli en el Pacifico mexicano. Ciencia Pesquera 1(1):45–52 INP, México.

4. Márquez, R. and Carrasco, M. 1993. Resumen de playas de anidación de tortugas marinas, reservas naturales y actividades de conservación. INP/CRIP-Manzanillo. 21 pp.

5. Pritchard, P.C.H. 1982. Nesting of the leatherback turtle, Dermochelys coriacea in Pacific Mexico, with a new estimate of the world population status. Copeia 1982(4):741–747.

6. Sarti, L., López, C., García, N., and Karam, S. 1994. Resultado de las actividades de protección de las tortugas golfina Lepidochelys olivacea y laúd Dermochelys coriacea en el Playón de Mexiquillo, Mich. Temporada 1993–94. In: Silva, F. (Comp.). Memorias del XI Encuentro Interuniversitario sobre Tortugas Marinas en Me´xico. San Patricio-Melaque, Jalisco, México. 12–18 Junio, 1994.

7. Sarti, L., 2000. Dermochelys coriacea. En: IUCN Red List of Threatened Species. www.redlist.org, Descargado 11 de Junio de 2004.

8. Sarti, L., A.R. Barragán, D. García, N. García, P. Huerta and F. Vargas. 2007. Conservation and biology of the leatherback turtle in the Mexican Pacific. Chelonian Conservation and Biology 6(1): 70-78




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APPENDIX I: FOTOGRAPHS OF FIELD ACTIVITIES

Community members excavate nests at Mexiquillo Nest relocation at Tierra Colorada

Protected hatchery in Cahuitán Protected hatchery in Barra de la Cruz

Clutch relocation in Cahuitán Hatchlings being released



Documents

“CONSERVATION OF LEATHERBACK TURTLES IN THE MEXICAN … · 2020. 1. 21. · Conservation of leatherbacks in Mexico Season 08-09 1 BACKGROUND The leatherback turtle (Dermochelys