|Eng-Heng Chan, Ph.D.|
|Professor, Centre for Turtle Research and Conservation
University College of Science and Technology Malaysia
|Effects of Incubation Temperature on the Sex Ratios of River Terrapin (Batagur baska) Eggs|
|Location: Setiu River, Terengganu, Malaysia|
|Species: River terrapin (Batagur baska)|
Abstract: This project is part of a comprehensive research and conservation program on the river terrapins of the Setiu River in Terengganu, Malaysia. It will address the specific and decades-old concern of temperature-dependant sex determination in the conservation of the species. The specific objectives of the project are:
The use of non-lethal methods in sexing of the terrapins will be crucial to the success of the overall program. Dr. Gerald Kuchling, who has successfully developed endoscopic sexing of small turtles will be a major collaborator in the project and is committed to provide the necessary training. The project will therefore have the added advantage of creating the opportunity to train Malaysian researchers in the non-lethal endoscopic sexing of river terrapins. The results of the project will provide the much-needed guidelines in the management of egg protection and incubation in river terrapin conservation programs carried out in Malaysia.
Project Report: December 2006
Viable wild populations of the critically endangered river terrapin, Batagur baska, are believed to occur mostly in Malaysia. Here, conservation programs involving egg protection in hatcheries, head-starting and release of head-started terrapins in five river systems have been in place since the 1970's. However, these efforts have not manifested in population recovery. One of the concerns is that artificial incubation of eggs may have resulted in the possibility of the production and subsequent release of either all-male or all-female terrapins, or even inter-sexed terrapins into the wild.
A major constraint to the study of temperature-dependant sex determination in critically endangered turtles in the past was the lack of a non-lethal method to assess the sex of small turtles. The recent development of endoscopy and its successful application for large-scale sexing of captive-raised juvenile Erymnochelys madagascariensis, by Dr. Gerald Kuchling, has now provided opportunities to address the decades-old concern of releasing sex-biased or inter-sexed river terrapins into the natural environment. The inclusion of Dr. Gerald Kuchling, who pioneered the use of endoscopy in sex-determination of turtles, as a major collaborator in this project helped ensure its success and provided the opportunity to train Malaysian researchers in the non-lethal endoscopic sexing of river terrapins.
Perak Head-Starting Facility in Bota Kanan:
Of 15 four-year old sub-adults, (537 - 858 g) sexed, 3 were male and 12 were female terrapins. An additional 6 eight-month old hatchlings (83-225 g) examined yielded 4 male and 2 female terrapins.
Terengganu Head-Starting Facility in Bukit Paloh:
The general conclusion on the sex-ratio of the rivers terrapins incubated in the head-starting facilities of Malaysia is that in some years, 100% female hatchlings were produced and in other years, both females and males were produced. The sex-ratio output probably related to ambient temperatures prevailing in different years.
The findings are now directly applied to the ex-situ incubation of river terrapin eggs in the Setiu River terrapin conservation project in order to produce a mixed ratio of male to female river terrapins. They will also be incorporated into a report to be submitted to the Department of Wildlife and National Parks Malaysia. The report will specifically propose the modification of current ex-situ incubation methods in order to ensure that river terrapins of both sexes are produced for the various head-starting facilities managed by the department.
Modifications to existing ex-situ egg incubation methods will ensure the production of both male and female river terrapins for restocking purposes. In the long-term, wild terrapins will have enhanced chances of survival as the presence of both male and female individuals will result in adequate mating chances and ensure the production of fertilized egg clutches.
I feel that I have been personally enriched in the process of conducting this project. Firstly, it has helped me establish working relations with Dr. Gerald Kuchling who pioneered the application of endoscopy in non-lethal sex determination of turtles. I then entered the project in a Research and Development Exhibition in Malaysia and was awarded a consolation prize. Last year, the project brought me to South Africa for the first time, to present a paper entitled "Sex Ratios of River Terrapins (Batagur baska) in the Head-Starting Facilities of Malaysia" at the 5th World Congress of Herpetology. Later in the same year, Cleveland Metroparks Zoo invited me to San Diego to attend the 2005 Turtle Survival Alliance General Meeting to present a talk on the River Terrapin Project, followed by a visit to the Cleveland Metroparks Zoo where I also gave a seminar on the River Terrapin Project. Hence this is one project that has not just fulfilled its major and specific objectives, but has helped in the personal development of its executant as well.
Project web page: http://www.kustem.edu.my/ctrec/