02449nas a2200193   4500008004100000245004200041210004200083520193200125653001702057653001202074653001102086653001302097653002002110653001202130653001502142100002002157700002202177856005602199       2021                        eng d00aUsing bioacoustics to monitor gibbons0 aUsing bioacoustics to monitor gibbons3 a<p>Monitoring wildlife population trends is critical for the conservation of endangered species and measuring the efficacy of management activities. Recently, passive acoustic monitoring has emerged as a useful wildlife monitoring tool and automatic recorders have been used to detect the presence of gibbons in protected areas of Vietnam. However, these recording devices can be expensive, cumbersome, and difficult to operate in some areas with gibbons. Therefore, inexpensive, lightweight, and easily operated recording devices are needed for wildlife monitoring. In this study, we employed mobile smartphones to detect the presence and distribution, and to estimate the occurrence probability, of the northern yellow-cheeked crested gibbon (Nomascus annamensis) in Dakrong Nature Reserve (405.3 km2), Vietnam. We surveyed gibbons from February to July 2019, during the dry season, at 95 sites that were systematically spaced throughout the nature reserve. We used the software package, RAVEN, to analyze the sound data and to identify gibbon calls. We detected gibbon calls at 39 out of 95 recording sites. With these data and an occupancy model, we estimated, and examined the effects of environmental factors, on the occurrence probability. Assuming a 600 m detection distance, the model-averaged occurrence probability for the nature reserve was 0.44 (SE = 0.06). The area of rich (&gt; 100 m3/ha) and medium (&gt; 200 m3/ha) evergreen forest within 1 km of the recording posts was the most important predictor of, and posi- tively correlated with, occurrence with less occurrence in poor, regrowth forest, planta- tions, or on bare land. Bioacoustic methods can be potentially used in large-scale gibbon surveys, and the technology is especially attractive given the low cost. Additional work on estimating detection distances and identifying individual gibbon groups using bioacoustics will be useful next steps.</p>
10abioacoustics10aDakrong10aGibbon10aNomascus10aOccupancy model10aprimate10aSmartphone1 aVu, Thinh, Tien1 aDoherty, Paul, F.  uhttp://link.springer.com/10.1007/s10531-021-02139-1