Discovering threatened freshwater turtles by an innovative floating camera trap system

Camera traps are widely used for terrestrial wildlife monitoring but remain underutilized for aquatic species due to inherent challenges in freshwater environments. Freshwater turtles, particularly the critically endangered Swinhoe's softshell turtle (Rafetus swinhoei), are notoriously difficult to observe in the wild. Here, we present a novel floating camera trap system specifically designed to enhance the probability of detecting this elusive species in a historical habitat. Seven floating camera traps were deployed in a lake in northern Vietnam, operating for a cumulative 420 camera-trap days and capturing 33,846 images. Among these, one image documented the head of a large softshell turtle exhibiting morphological characteristics apparently consistent with only R. swinhoei, providing critical evidence of its likely continued presence in the wild. Additionally, the system recorded multiple freshwater reptile species, including other threatened turtles, demonstrating its broader applicability for freshwater biodiversity assessments. Our results confirm (i) the effectiveness of floating camera traps in detecting freshwater species and (ii) the potential survival of R. swinhoei in northern Vietnam, a pivotal finding for global turtle conservation. The system is lightweight, cost-effective, and easily replicable, offering a scalable tool for non-invasive monitoring of freshwater ecosystems and rare aquatic taxa.