Eng, Heng Chan

Liew, H. C.

Universiti Putra Malaysia Institutional Repository

UPM Research Report 1998: Volume 2IN SITU INCUBATION OF SEA TURTLE EGGS ATCHAGAR HUTANG, PULAU REDANGEng Heng Chan and H.C. LiewFaculty of Applied Science and TechnologyUniversiti Putra Malaysia Terengganu, Mengabang Telipot,21030 Kuala Terengganu, MalaysiaKeywords: sea turtle, egg incubation, conservation, bi-ology.IntroductionIn many of the sea turtle conservation programmes in Malay-sia, eggs are incubated and protected in beach hatcheries.There are arguments against this approach as hatch successmay be compromised and the hatchlings produced are sex-biased since the hatcheries are usually fully exposed to solarradiation and subjected to high incubation temperatures.This study was therefore designed to introduce in situ incu-bation and to demonstrate that this technique is viable andprovides an alternative to sea turtle egg incubation and pro-tection programmes in the country. It also seeks to investi-gate the factors that may account for hatch failure undernatural conditions. The study highlights the complimentaryrole which universities can perform in sea turtle conserva-tion.Materials and MethodsEgg clutches deposited in the months of AprillMay to 31August of 1993 to 1998 in Chagar Hutang beach, PulauRedang were purchased from licensed egg collectors atRMl10.00 and RM120.00 per clutch for green and hawksbillturtles respectively for incubation. The nests were markedand left in their natural (in situ) nests to incubate to full-term.The entire beach was guarded round the clock to ward offnatural predators and potential human poachers. The nestswere inspected several times per day for signs of predation orhatchling emergence and activity. Emerging hatchlings werenot restrained but allowed to crawl naturally to the sea. Afew days after hatchling emergence, each nest was excavatedto determine number of hatchlings emerged (from number ofempty hatched shells), number of dead and live hatchlings inthe nest, and number of unhatched eggs. Mortality factorssuch as damage by nesting turtles, depredation by monitorlizards, ants, crabs and plant roots were also recorded foreach nest. Emergence success was computed based on thenumber of healthy live hatchlings produced from each nest.Data from individual nests were summed to provide data onyearly output of hatchlings.Results and DiscussionThe number of egg clutches incubated per year from 1993 to1998 ranged from 202 to 401. At RMlO1.00 per clutch, thefunds disbursed for egg purchase have ranged fromRM22,220 to RM44,210 per year. The egg clutches incu-228bated represented 51 to 95% of the clutches deposited inChagar Hutang during the period of egg purchase. Our rec-ords indicate that in recent years (1997-98), egg collectorshave become more willing to sell their eggs to the project forincubation, as opposed to removing them for sale in the mar-kets. The egg clutches purchased translated to a range of18,700 to 38,122 eggs incubated per year. This represented33,36,46, 75, 68 and 71% of the total number of eggs incu-bated for the whole of Pulau Redang from 1993 to 1998 re-spectively. These figures indicate that our in situ egg incu-bation programme is assuming an increasingly important rolein turtle conservation in the island. This is not surprising asChagar Hutang is the major nesting beach in Redang, and ac-counts for 41 to 58% of the total egg production. The Fish-eries Department protects eggs deposited in Mak Kepitwhich accounts for 20 to 30% of the island's egg production.The combined efforts of UPMT and the Fisheries Depart-ment protect only 37 to 61% of total egg production inRedang each year. This level of protection is inadequate forpopulation sustainability. Turtle conservationists recom-mend that at least 70% of the eggs be protected in order thatnesting populations can be maintained at their current levels.Emergence success attained have ranged from 78 to 82%.The differential rates obtained from year to year are a reflec-tion of the varying effects of mortality factors. These ratescompare favourably with those reported for green turtleselsewhere (Whitmore and Dutton, 1985; Fowler, 1979).Hatch rates from hatcheries usually average about 70%.Predators of eggs and hatchlings in Chagar Hutang includedmonitor lizards (up to 11% of nests affected), ghost crabs(22%), hermit crabs 2%), and ants 22%). Other mortalityfactors were the nesting activities of turtles (up to 2% ofnests affected) and plant root invasion (33%). Althoughthese factors lowered emergence success, their effects did notappear to pose serious threats to the success of in situ nests.ConclusionsThis stu~y demonstrates that in situ incubation of turtle eggsc.anbe highly su:cessful and is superior to the common prac-tice of hatchery Incubation. Although natural mortality fac-tors are present, their effects do not pose threats to the suc-cess of in situ nests. Universities can play an important rolein turtle conservation and help to increase the level of eggprotection achieved in government programmes. However,~e nec~ssity of disbursing funds for the purchase of eggs forl~cubatIon renders turtle conservation is an expensive exer-cise. Local authorities should be urged to rethink the dec-ades-long practice of licensing egg collection.ReferencesFowler, L.E. 1979. Hatching success and nest predation in the greensea turtle, Chelonia mydas, at Tortuguero, Costa Rica. Ecology.605: 946-955.Whi~ore, C.P. and Dutton, P.H. 1985. Infertility, embryonic rnor-~ty ~d nest-site selection in leatherback and green sea turtlesID Sunname. Biological Conservation. 34: 251-272.Supported ITy IRPA Grant 01-02-04-0173

In situ incubation of sea turtle eggs at Chagar Hutang, Pulau Redang

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In situ incubation of sea turtle eggs at Chagar Hutang, Pulau Redang

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