Implementation of a new monitoring protocol at Tortuguero, Costa Rica

Sebastian Troëng
Caribbean Conservation Corporation, Apartado Postal 246-2050, San Pedro, Costa Rica

A new monitoring protocol was implemented in Tortuguero, Costa Rica, during the 1998 green turtle Chelonia mydas nesting season. Compared to previous years, the protocol included several new activities at the expense of decreased effort of nightly tagging.

Results from track surveys indicate that the number of green turtle nests in 1998 was one of the highest since weekly track surveys were initiated in 1971. During night patrols, a total of 1,225 green turtles were tagged, 286 green turtles with tags from previous years were encountered, and 3 green turtles (Panama 2, Mexico 1) tagged at other sites were seen. Green turtles with evidence of old tag holes or notches in at least one flipper represented 10% of newly tagged turtles. The probability of within-season inconel tag loss was estimated at 0.019.

Fibropapilloma incidence amounted to 2.1% with none of the affected turtles showing evidence of prior tagging. Carapace length (CCLmin) ± ST.D. for nesting green turtles was 103.6 ± 5.4cm and mean clutch size ± ST.D. was 108.6±20.9 eggs.

Hatching success for 196 marked nests was 62.8%, and emerging success for 193 marked nests was 60.0%. Of marked nests, 15.3% were disturbed by nesting turtles, 6.7% were illegally harvested by humans, 1.5% were depredated by natural predators, and 1.0% were depredated by dogs.

Rainfall varied from 80.9 mm per month (September) to 430.6 mm (June). Sand temperature was higher for the month with the least rainfall (September).

A total of 16,972 tourists paid US$5-US$25 per person to go on guided turtle walks at Tortuguero, during June- October. It is anticipated that these results will aid in management and increase interest in green turtle conservation on regional, national and local levels.

The monitoring program in Tortuguero was coordinated by Caribbean Conservation Corporation and implemented under a research permit from the Ministry of Environment and Energy of Costa Rica. The protocol for monitoring was developed by staff and Scientific Advisory Committee of Caribbean Conservation Corporation. Data was collected by the many research assistants and program participants whom are thanked for their hard work and long hours on the beach.

Abstract of paper presented at 19th International Symposium, 1999