High freshwater turtle occupancy of streams within a sustainably managed tropical forest in Borneo

Abstract

Despite suffering dramatic declines due to habitat loss and overexploitation, tortoises and freshwater turtles in Southeast Asia remain understudied. Sustainable forest management offers a promising approach for advancing the conservation of threatened turtle populations. This study examines the effect of reduced impact logging (RIL), a sustainable forestry method, on 2 freshwater turtle species. We examined detectability patterns and habitat relationships for the threatened Malayan flat-shelled turtle (Notochelys platynota) and the non-threatened Malayan soft-shelled turtle (Dogania subplana) in 8 streams within a commercial forest reserve between March and July 2019, in Sabah, Malaysian Borneo. Using single-species occupancy models, we identified covariates associated with the detection and occupancy probabilities of these species across a post-harvest recovery gradient (1–21 years since logging). Covariates used in the models were obtained directly from the field or from open-source remote sensing data. Results for soft-shelled turtles were inconclusive. In contrast, we found a negative association between monthly rainfall and flat-shelled turtle detectability. The occupancy probability of flat-shelled turtles was positively associated with greater distance from logging roads and higher stream flow accumulation. Occupancy probability for flat-shelled turtles and soft-shelled turtles was relatively high throughout the reserve (0.79 ± 0.1 [SD] and 0.57 ± 0.22, respectively). These results, suggest that appropriately managed forests, could serve as invaluable conservation areas for imperiled freshwater turtle species in the region.