Using eDNA techniques to find the endangered big-headed turtle (Platysternon megacephalum)

Ivan P. Y. LAM, Yik-Hei SUNG, Jonathan J. FONG*

*Corresponding author for this work

Research output: Journal PublicationsJournal Article (refereed)peer-review

9 Citations (Scopus)


We evaluate the efficacy of environmental DNA (eDNA) techniques to locate wild populations and estimate the population size of the endangered big-headed turtle (Platysternon megacephalum) in Hong Kong. The results from this study are important for identifying priority sites for protection and further research. Additionally, we assess the impact of two environmental variables (temperature and pH) on eDNA quantity. We surveyed 34 streams for three years, sampling four times each year. Four new populations were first identified with eDNA analysis, and then verified by field surveys. Our multi-year survey highlights that eDNA detection can be inconsistent over time, even in streams with known populations. There was no significant relationship between eDNA quantity and the environmental variables tested. Lastly, our results suggest that eDNA methods remain promising to estimate population size, since number of positive detections were positively correlated with population size in streams with known populations. We conclude that eDNA methods are powerful, but care must be taken when interpreting field results as they are affected by species ecology and environmental conditions.
Original languageEnglish
Article numbere0262015
JournalPLoS ONE
Issue number2
Early online date7 Feb 2022
Publication statusPublished - 7 Feb 2022

Bibliographical note

Funding Information:
The sources of funding of the work submitted are as follows: 1. Research Grants Council of Hong Kong (Early Career Scheme #23100216), from The Government of Hong Kong Special Administrative Region; received by J.J.F. (URL: 2. Environment and Conservation Fund (#ECF2017-04), from The Government of Hong Kong Special Administrative Region; received by Y.H.S. (URL: 3. Ocean Park Conservation Foundation Conservation Fund (#RP01.1718), from Ocean Park Conservation Fundation Hong Kong; received by Y. H.S. (URL: 4. Croucher Foundation Chinese Visitorship (#870026), from Croucher Foundation; received by J.J.F. (URL: enabling-the-exchange-of-ideas-between-hongkong-scientists-and-their-counterparts-inmainland-china-and-overseas/croucher-chinesevisitorships) The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. We thank the following people for invaluable discussions on eDNA: Kathryn Stewart, Caren Goldberg, David Pilliod, Tracie Seimon, and Brian Horne. We would also like to thank the team that helped with fieldwork: Jose Wellington Alves dos Santos, Anchalee Aowphol, Liu Lin, Li Ding, Fengyue Shu, Itzue Caviedes Solis, Abby Bauer, Hing Fong Cheung, Siu Chung Lo, and Siu Yin Yu.

Publisher Copyright:
© 2022 Lam et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.


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