In Search of One of the Most Endangered Turtles in the World, the Vietnamese Pond Turtle ( Mauremys annamensis ), Using Environmental DNA

ABSTRACT The Vietnamese Pond Turtle, Mauremys annamensis , is a species endemic to Central Vietnam. Its population has experienced a significant decline over the past several decades primarily due to habitat loss and targeted overexploitation for food, the international pet trade, and use in traditional medicine. As a result, this species has been listed among the 25 most endangered turtles in the world and considered likely extinct in the wild. This poorly studied species has only been recorded four times in its natural habitat using traditional survey methods, and its distribution remains largely unknown. In this study, we utilize an environmental DNA method to assess the distribution of M. annamensis across various habitats, including ponds, lakes, and shallow streams, in four provinces (Quang Nam, Quang Ngai, Phu Yen, and Dak Lak) in Central Vietnam. Our findings demonstrate that it is possible to detect M. annamensis ' DNA in the aquatic habitats, even where the species has not been observed in the areas. Furthermore, our results provide the first evidence of the species' presence in Ea So Nature Reserve, a protected area in Dak Lak Province, where this turtle had not previously been documented in the wild. This discovery is crucial for informing conservation strategies by identifying a new candidate site for reintroduction programs for one of the most endangered turtles in the world, which currently has no known viable wild populations. Our results can help guide future eDNA surveys of this and other aquatic turtle species by focusing on suitable habitats and breeding seasons and promote the broader application of eDNA to assess distribution and population status of other threatened species in Vietnam.