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/s10531-021-02139-102567nas a2200205   4500008004100000022001400041245006500055210006200120260001600182520197800198653001702176653001102193653001202204653001202216653002202228653001502250100002002265700002102285856005502306       2019                        eng d  a0164-029100aAn Application of Autonomous Recorders for Gibbon Monitoring0 aApplication of Autonomous Recorders for Gibbon Monitoring  cOct-01-20193 a<p>Population monitoring is very important in wildlife management and conservation. All 18 species of gibbons are considered threatened with extinction and listed on the IUCN Red List of Threatened Species. Thus, understanding and effectively monitoring their population trends and distribution are critical. Thus far, all gibbon surveying and monitoring programs have been conducted by human surveyors; this is expensive, laborious, and dependent on the surveyors&rsquo; skills. In particular, estimating group density often requires a large sample size with several skilled observers working simultaneously in the field. We used autonomous recorders to record the calls of southern yellow-cheeked crested gibbon (Nomascus gabbrielae) for at least 3 days at each of 57 posts in Nam Cat Tien sector, Cat Tien National Park, Vietnam from July to October, 2016. We extracted gibbon calls from the recordings auditorily or visually using spectrograms in RAVEN software. We detected gibbon calls at 40 recording posts during the survey. The proportion of recorders with gibbon calls in the eastern region of Nam Cat Tien sector (mean&thinsp;=&thinsp;0.79; SE&thinsp;=&thinsp;0.13) was higher than that in the western region (mean&thinsp;=&thinsp;0.46; SE&thinsp;=&thinsp;0.11). The estimated probability of occurrence in the eastern region (&psi;&thinsp;=&thinsp;0.56; SE&thinsp;=&thinsp;0.20) was higher than that in the western region (&psi;&thinsp;=&thinsp;0.23; SE&thinsp;=&thinsp;0.16). Passive acoustic data were useful to investigate spatial variation in the probability of occurrence of gibbon. We recommend using autonomous recorders combined with occupancy model to complement human surveyors in gibbon monitoring in areas with low gibbon density because it is efficient, low cost, and not subject to errors caused by human surveyors. In the areas of high gibbon density, absolute density estimate achieved by human surveyors might be a more suitable indicator.</p>
10abioacoustics10aGibbon10aNomascu10aprimate10as Occupancy model10aSong meter1 aVu, Thinh, Tien1 aTran, Long, Manh  uhttp://link.springer.com/10.1007/s10764-018-0073-3