Archaeological Bone Assemblages Trace Changes in Turtle and Tortoise Diversity in Continental Southeast Asia
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Abstract
Among tropical regions, continental Southeast Asia is a major hotspot of biodiversity. However, due to rapid urban expansion and severe deforestation, this area is recognized as one of the top global conservation priorities. As in other tropical regions, the prevailing idea is that the decline of local biodiversity in this region is a direct result of the overwhelming environmental changes that have occurred over the last 80 years. However, paleoecological data indicate that tropical forests have been exploited by human populations since at least the Late Pleistocene, and forest clearance for farming began several thousand years ago. To gain a complete overview of the long-term evolution of vertebrate fauna in continental Southeast Asia, it is necessary to investigate the past. This task is currently out of reach, mainly due to the lack of paleontological and historical studies regarding small animals, including emblematic taxa like turtles. Indeed, although some evidence suggests that the biodiversity of turtles in continental Southeast Asia may have changed over the last millennia, the paucity of historical records and archaeological assemblages studies currently precludes further assessment of the potential effect of past environmental changes, including potential human disturbances. The present study consists of a paleontological analysis of turtle bone assemblages collected from four prehistoric sites in Thailand and Cambodia. The aim is to test the hypothesis of changes in turtle biodiversity over the last 10,000 years. Our results indicate that turtle assemblages in most areas have experienced only limited changes across the Holocene, except for Laang Spean in Cambodia. However, a few rare taxa may represent extirpated or extinct species of Testudinidae in continental Southeast Asia at an unknown time during the Holocene. We also observed significant changes in the geographic distribution of some genera, such as Batagur , Cyclemys , and Amyda . The fact that turtle fauna has been rather resilient and unchanged for several millennia shows that past human impact in most investigated areas had limited effects on these taxa. The strong modifications observed in Cambodia could, however, serve as a warning about the potential fate of turtle biodiversity in this region if further loss of natural environments occurs.
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The majority of Mainland Southeast Asia, the so-called Indo-Burma region, is considered a biodiversity hotspot (Myers et al., 2000). This region hosts a great diversity of freshwater turtles and tortoises (Turtle Taxonomy Working Group, 2021), many of which are threatened, but little is known about the evolution of this diversity and of the distribution of species over the past millennia. Indeed, it is important to understand whether the decline of modern turtle populations is the result of increased human impact during the last century or if it started well before that. In this context, the idea of re-evaluating zooarcheological assemblages to estimate past turtle diversity is quite pertinent. Using this method, it was shown that turtle diversity in the central plain of Thailand was higher during the Neolithic and Iron Age (Claude et …
The majority of Mainland Southeast Asia, the so-called Indo-Burma region, is considered a biodiversity hotspot (Myers et al., 2000). This region hosts a great diversity of freshwater turtles and tortoises (Turtle Taxonomy Working Group, 2021), many of which are threatened, but little is known about the evolution of this diversity and of the distribution of species over the past millennia. Indeed, it is important to understand whether the decline of modern turtle populations is the result of increased human impact during the last century or if it started well before that. In this context, the idea of re-evaluating zooarcheological assemblages to estimate past turtle diversity is quite pertinent. Using this method, it was shown that turtle diversity in the central plain of Thailand was higher during the Neolithic and Iron Age (Claude et al., 2019).
Here, Bochaton et al. (2025) re-evaluate turtle bone assemblages from four archeological sites in Thailand and Cambodia dated from the Late Pleistocene to the Iron Age. Taxonomical identifications are clearly justified, and supplementary plates documents the shell bone morphology of several Southeast Asian species, which will prove useful for future work of comparative anatomy. The results are somewhat counter-intuitive because they mostly show a certain stability of the composition of turtle communities in the region, with only some shrinkages in distribution and possibly the (local?) extinction of one or several species of Testudinidae.
The authors also discuss the limits of this method. Indeed, bone accumulations in archeological sites are the result of human action and so are not unbiased images of past diversities. For example, the tortoise Indotestudo elongata is by far the most abundant turtle species in the four studies sites and was obviously favored by human populations at the time (Bochaton et al., 2023). However, the sampling of the much less common freshwater turtles appears to be fairly exhaustive as it matches that of modern environments in the region, which strengthens Bochaton et al. (2025)'s conclusions.
This is an important study that calls for more.
References
Bochaton, C., Chantasri, S., Maneechote, M., Claude, J., Griggo, C., Naksri, W., Forestier, H., Sophady, H., Auertrakulvit, P., Bowonsachoti, J., Zeitoun, V. (2023). Zooarchaeological investigation of the Hoabinhian exploitation of reptiles and amphibians in Thailand and Cambodia with a focus on the Yellow-headed Tortoise (Indotestudo elongata (Blyth, 1854)). Peer Community Journal, 3, e94. https://doi.org/10.24072/pcjournal.328
Bochaton, C., Naksri, W., Chantasri, S., Maneechote, M., Mithong, S., Heng, S., Forestier, H., Auetrakulvit, P., Zeitoun, V., Bowonsachoti, J., Claude, J. (2025). Archaeological Bone Assemblages Trace Changes in Turtle and Tortoise Diversity in Continental Southeast Asia. bioRxiv, 645446, ver. 3 peer-reviewed by PCI Paleo. https://doi.org/10.1101/2025.03.27.645446
Claude, J., Auetrakulvit, P., Naksri, W., Bochaton, C., Zeitoun, V., Tong, H. (2019). The recent fossil turtle record of the central plain of Thailand reveals local extinctions. Annales de Paléontologie, 105(4), 305–315. https://doi.org/10.1016/j.annpal.2019.04.005
Myers, N., Mittermeier, R. A., Mittermeier, C. G., Da Fonseca, G. A. B., Kent, J. (2000). Biodiversity hotspots for conservation priorities. Nature, 403(6772), 853–858. https://doi.org/10.1038/35002501
Turtle Taxonomy Working Group [Rhodin, A. G. J., Iverson, J. B., Bour, R., Fritz, U., Georges, A., Shaffer, H. B., van Dijk, P. P.]. (2021). Turtles of the World: Annotated Checklist and Atlas of Taxonomy, Synonymy, Distribution, and Conservation Status (9th Ed.). Chelonian Research Monographs 8:1–472. https://doi.org/10.3854/crm.8.checklist.atlas.v9.2021
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