Hugh Govan^1,2

Members of ADECORO monitor turtle nesting and nest predation. Daily patrols are carried out at first light and data are collected regarding species (from track morphology), nest location and any nest destruction events (mainly by dogs and humans). Further details are provided in Drake (1993) and Govan and ADECORO (1996).

Four species of turtle are thought to nest on the Pacific coast of Costa Rica (Cornelius 1995). These are the olive ridley (Lepidochelys olivacea), Pacific green (Chelonia mydas agassizi), leatherback (Dermochelys coriacea) and hawksbill (Eretmochelys imbricata) turtles. At Río Oro, a minimum of 2,860 nests were laid in 1994 and species identification was possible in 2,423 cases (Table 1). In 1996, a total of 3,162 were laid. Most nesting is by olive ridley turtles, with relatively low numbers of green turtles and leatherback turtles. Hawksbill turtles are reported to occur by local inhabitants but none were positively identified at Rio Oro in 1994 or 1996.

Although nesting is recorded in all months of the year, each of the species recorded have a seasonal peak of activity (Table 1). Nesting levels show marked spatial variation and in some 100m stretches, densities reach an equivalent of 840 nests/km/year.

Table 1. Breakdown of marine turtle nests recorded in 1994,

with an indication of the peak of nesting for each species.

The Pacific coast of Costa Rica hosts some of the most spectacular mass nesting phenomena in the world during which hundreds of thousands of olive ridley turtles participate in "arribadas" on the beaches of Nancite and Ostional (Cornelius 1986, 1995). However, hatching success of these nests can be very low (<10%). The hatching success rate at solitary or medium intensity nesting beaches, such as Río Oro, can be much higher (Castro 1986; this study). These observations may lend some support to the hypothesis that it is the solitary or medium intensity nesting beaches that maintain population levels of olive ridley turtles (Castro 1986), possibly increasing the biological importance of nesting beaches such as Rio Oro.

Table 2 shows the monthly total of nests destroyed by dogs in both 1994 and 1996. In June 1996, ADECORO started community-based management of the beach which involved both the participation of community members in controlling movements of their animals, and the removal of feral dogs which was carried out in conjunction with local authorities. A marked reduction can be seen in predation levels subsequent to the commencement of this initiative. It is almost certain that the reduction of dog predation is the result of a combination of the activities of the beach patrols and general increasing awareness in the community. This increased awareness is likely to have contributed to the decrease in the activities of human egg collectors. The number of nests collected by humans fell from 344(12%) in 1994 to 122 (4%) in 1996.

Table 2. Turtle nests destroyed by dogs in 1994 (of 2,860 nests) and 1996 (of 3,162 nests)

(*=subsequent to dog control programme)

Recently, a more serious threat has come to light in the form of proposed plans for a hotel and tourism development of the coastal strip. Developments are proposed to be implemented within a year. It is recommended that a degree of legal protection should be given to the coastal strip at Río Oro and this area should be managed by, or in very close collaboration with, the local community through a local association such as ADECORO. The coastal strip could then serve as a buffer zone between developments and the nesting beach. Developments affecting the nesting beach should take into account both the vulnerability of the resource and the need of the local community for sustainable alternative livelihoods. The community could then benefit from their management actions through a variety of sustainable activities, particularly eco-tourism. ADECORO is currently negotiating with the Ministry of the Environment and other interested parties in order to achieve these aims.

Acknowledgements: We would like to thank the following organisations for financial support: The Chelonia Institute, US Fish and Wildlife Service through the Aquatic Resources Conservation Group, Secretaria de Estado para la Cooperación Internacional y para Iberoamérica, Ministerio de Asuntos Exteriores de España (SECIPI) through the Asociación para el Estudio y Defensa de los Ecosistemas Marinos (AEDMAR). We also wish to acknowledge the invaluable work of Tierras Unidas Vecinales para el Ambiente (TUVA) and numerous local participants and foreign volunteers.