Infertility, embryonic mortality and nest-site selection in leatherback and green sea turtles in Suriname

Abstract

Nest-site selection and causes of non-viability in eggs of leatherbacks Dermochelys coriacea and green turtles Chelonia mydas were investigated for two consecutive seasons on a beach used for nesting by both species in Suriname. Examination of nests and artificially incubated clutches after hatching showed that the main cause of an interspecies difference in hatching success was higher embryonic mortality in leatherbacks. Rupturing of eggs, used as an index of predation, was also greater in leatherback nests. Although infertility was slightly higher in leatherbacks, it was relatively low in both species. An interspecies difference in nest-site selection was found, with leatherbacks laying predominantly in open sand and green turtles in vegetated areas. Hatching success in the different areas was similar for green turtles, but only 12% of green turtle nests were occasionally washed over by sea swell compared to 40% of leatherback nests. Washover caused embryonic mortality in both species and is one of the causes of the increased embryonic mortality in leatherbacks. However, embryonic mortality was also higher in leatherback than in green turtle nests that were not washed over. Approximately half of the embryonic mortality occurred before days 22–24 of incubation in both species. Artificial incubation produced hatching successes similar to those in nests laid above spring high tide level. Predation was eliminated in styrofoam boxes and reduced in reburied clutches. Increased embryonic mortality during late development was found in the boxes. The implications for conservation of sea turtles are discussed.