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Marine Turtle Newsletter 58:9-10, © 2001

Hatching Success of Wave-Tossed Loggerhead Turtle Eggs

Gilbert S. Grant and Beverly B. Green
Topsail Turtle Project, Post Office Box 2663, Surf City, North Carolina 28445 USA

Sea turtle eggs are sensitive to turning shortly after laying. For this reason, nests that must be relocated should be moved within 12 hours of laying or after two weeks of incubation time has elapsed (Limpus et al., 1979). During early development reptile embryos become attached to the inner surface of the egg shell. During relocation, great care must be exercised to minimize turning of the eggs or the tiny embryo will be dislodged. High mortality in relocated eggs is thought to be caused by rotation (e.g., Bustard, 1972). We report here the hatching success of loggerhead sea turtle (Caretta caretta) eggs unearthed by heavy surf after an estimated four weeks of incubation.

At about 1500 hr on 2 September 1991, Russell Proctum and his daughter watched as a retreating wave exposed nearly 100 loggerhead turtle eggs from a nest at North Topsail Beach, Onslow County, North Carolina. Eggs that were rolling in the surf were hastily picked up and transferred to higher ground. Proctum estimated 10-15 eggs were lost with the outflowing wave. A total of 75 eggs were retrieved and buried on higher ground. At about 1730 hr, Grant arrived at the beach and relocated the eggs a second time to a more stable part of the beach (the temporary burial site chosen by the Proctums was in a low lying over-wash area subject to heavy human traffic). The new nest cavity was excavated to the dimensions of a natural nest and all 75 eggs were placed in it within 30 minutes. The date the eggs were originally laid is not precisely known. One egg reburied on 2 September was yellowish in color which suggested it was infertile or the embryo had died at an early age.

The relocated nest site was visually checked daily by Green. On 19 October 1991, two hatchlings emerged; on 21 October, a third hatchling emerged and made its way to the ocean. On 30 October we exhumed the nest to examine its contents. Two live hatchlings were encountered in the nest and were released after dark. Three eggs had no discernible embryo, 61 had dead embryos <3 cm in length, five had dead embryos >3 cm in length, and one egg held a dead pipped turtle (total = 75 eggs). All unhatched eggs appeared more desiccated (wrinkled and dented) than usual. Ocean salt adhering to the shells may have osmotically pulled water out of the eggs. Low nest humidity will also desiccate eggs (McGehee, 1990), but eggs in nests nearby in sand of similar moisture content did not appear to be desiccated.

Assuming (1) an incubation period of about 70-80 days for eggs laid this late in the season, and (2) that the pulse of mortality was directly related to disturbance caused by wave action on 2 September, then the eggs were probably laid during early August and the 61 dead embryos <3 cm in length were approximately 20-30 days old. Another late-season clutch laid on 13 August 1991 required 76 days for incubation (Jean Beasley, pers. comm.). The rolling in the surf, salt exposure, and subsequent handling most likely contributed to the high mortality. Despite the observed low hatch rate, 6.6% (5/75) of the eggs resulted in hatchlings that successfully entered the sea. This study points out the value of salvaging turtle eggs found recently exposed to the elements.

Acknowledgments. I thank Russell Proctum for his role in this study and Jean Beasley for reviewing the manuscript.

Bustard, R. 1972. Sea Turtles: Natural History and Conservation. Taplinger Publ. Co., New York. 222 p.

Limpus, C. J., V. Baker, and J. D. Miller. 1979. Movement-induced mortality of loggerhead eggs. Herpetologica 35(4):335-338.

McGehee, M. A. 1990. Effects of moisture on eggs and hatchlings of loggerhead sea turtles (Caretta caretta). Herpetologica 46(3):251-258.