As part of a study of nest-site selection and causes of non-viability in leatherback Dermochelys coriacea and green turtle Chelonia mydas eggs, artificial incubation of some clutches was undertaken. Hatch success was compared with natural nests on Krofajapasi beach, Wia-Wia Nature Reserve, Surinam.
The 12 km beach was patrolled at least once a week through the nesting seasons of April-August 1981 and March-August 1982. The number of nests of each species in each of three distinct vegetation zones (sand, <5% vegetation cover; border, 5-45% cover; and vegetation, 45-100% cover) were counted. Eggs incubated in one of three ways were studied:
1) natural nests (1981 - 41 green and 9 leatherback nests; 1982 - 39 green and 36 leatherback nests monitored);
2) eggs relocated from below spring high-tide level (prone to flooding) and reburied in a central sand plot (1982 - 13 leatherback clutches translocated, 50 eggs from each clutch reburied in hand-dug chambers);
3) incubated above ground in styrofoam boxes (1982 – 8 green turtle clutches, each of around 88 eggs placed per box; 11 leatherback clutches, 45 from each clutch per box).
Eggs and eggshells were examined after hatching. Ruptured eggs were used as an index of predation.
For leatherback and green turtles, artificial incubation produced hatching success similar to nests laid above the spring high tide level:
Natural nests - leatherback 52.4% (±4.0; n= 46) green 80.3% (±2.9; n=39);
Boxes - leatherback 59.9% (±7.0; n= 11) green 72.9% (±3.4; n=8);
Reburied - leatherback - 68.7% (±4.9; n=13).
Infertility rates were also similar:
Natural nests - leatherback 6.1% (± 2-3; n=30 eggs); green 1.6% (± 0.6; n=35);
Boxes - leatherback 7.0% (2.5 n=11); green 0.9% (+ 0.5 n=8);
Reburied clutches – leatherback 2.5% (± 1.4) n=13.
The main cause of difference in hatching success between species was higher embryonic mortality in leatherbacks. Predation was zero in styrofoam boxes and reduced in reburied clutches (6.3% ±2.8; n=14), compared to natural nests: leatherback 19.3% (±2.6; n=40); green 11.5% (±1.1; n=70).
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