How Can Monitoring of Hatching Success Inform Sea Turtle Management?

Andrea de Haro1, Sebastian Troëng2, Emma Harrison1
1 Caribbean Conservation Corporation, Apdo. Postal 246-2050, San Pedro, Costa Rica
2 Conservation International, 1919 M Street NW, Washington, DC 20036, USA

As at many sea turtle rookeries, natural green turtle hatching success data have been collected at Tortuguero, Costa Rica on an annual basis since 1998. We analyzed these data to determine if management strategies such as nest relocation and/or focused beach patrols by park rangers along specific sectors of the beach will help increase hatching success. To determine which variables influence green turtle hatchling production at Tortuguero, we analyzed hatchling production data from a sample of 1,416 green turtle nests laid 1998-2005 using a GAM model. The number of hatched eggs was the response variable and year, Julian date, beach zone, distance to the vegetation, distance to the high tide line, mile were used as potential cofactors. Only year, Julian date and beach zone had significant effects. It seems nests laid early during the nesting season produced fewer hatched eggs than nests laid later in the year. The model accounted for only 7% of the observed variance. As neither distance to the vegetation, high tide line or mile had significant effects, we conclude nest relocation is inappropriate as a conservation strategy for Tortuguero green turtle nests. However, graphically plotting of poaching rates along the northern five miles of nesting beach suggest rates are highest around Tortuguero village. Increased patrols by park rangers or local turtle spotters along this 800 m section of beach may help reduce illegal take of green turtle eggs.

Our analyses demonstrate that monitoring of hatching success can provide insights which allow for informed management. This may be preferrable to management decisions based on default practices or results from other nesting beaches.

Abstract of paper presented at 27th International Symposium, 2007