Using bioacoustics to monitor gibbons

Vu, Thinh Tien; Doherty, Paul F.

doi:10.1007/s10531-021-02139-1

Cited by 3 publications

(10 citation statements)

References 23 publications

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“…In our study, detection probability did not vary by date or time of day. Patterns of similar detection probability over days in wildlife monitoring using autonomous recorders have also been observed by Vu and Tran (2019) and Vu and Doherty (2021) in their studies with gibbons. This result suggests that using autonomous recorders in wildlife monitoring may be more objective than using human surveyors as the presence of humans can alter wildlife calling frequency (Vu & Tran 2019).…”

Section: Discussionsupporting

confidence: 72%

Using mobile smartphones and bioacoustics to monitor endangered bird species

Nguyen

Doherty

et al. 2023

Ibis

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Monitoring the status of endangered wildlife is a critical foundation for biodiversity conservation efforts. The use of autonomous acoustic recorders to monitor wildlife has become increasingly popular in terrestrial tropical systems. However, these recorders are expensive and not available for purchase and repair in all countries. The development of easy‐to‐use and low‐cost devices is therefore needed for applications worldwide. In this study, we modified and installed smartphone devices to operate and record sounds produced by the Vietnamese Crested Argus Rheinardia ocellata in Kon Chu Rang Nature Reserve, Vietnam, in 2021. We used the software package RAVEN to create spectrograms and to identify Crested Argus calls from acoustic recordings and used the program MARK to estimate occupancy and detection probabilities. We recorded calls of Crested Argus at 16 of 40 locations and most calls were recorded in the northern and eastern parts of the nature reserve. Our model‐averaged estimates of detection probabilities indicated that detection in the morning or afternoon was c. 0.50 and constant over seven sampling days. Our overall average occurrence probability of Crested Argus was 0.43 (standard error = ±0.08), but we found occupancy to be positively correlated with distance to the nearest village, indicating that poaching may negatively affect this species. Based on these data we suggest that the Kon Chu Rang Nature Reserve and possibly two adjacent nature reserves, namely An Toan Nature Reserve and Ba To Proposed Nature Reserve, might be important sites for Crested Argus.

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Section: Discussionsupporting

confidence: 72%

Using mobile smartphones and bioacoustics to monitor endangered bird species

Nguyen

Doherty

et al. 2023

Ibis

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“…Within each primary occasion, we considered survey days as secondary occasions in the closed population capture-recapture framework (Figure 4). We used the forest cover map of the Quang Tri Province (Scale 1:10,000; Quang Tri Forest Protection Department, 2016) to calculate the area of rich forest (>200 m 3 /ha) and medium forest (100-200 m3/ ha) in a 1 km radius circle from the recording post (forest) that was then used to model the occurrence probability in 2019 as Vu and Doherty (2021) found the "Forest" variable was most important in explaining variation in occurrence probability. We used the variables "Forest" and Distance to the nearest village (village), to model the apparent extinction and colonization probabilities since "Village" can influence the level of protection in the nature reserve, therefore, affecting the apparent extinction and colonization probabilities.…”

Section: Discussionmentioning

confidence: 99%

“…In 2019, a 2 ×2 km grid was overlaid on the map of the reserve (Vu & Doherty, 2021). This grid dimension ensured the independence among recorders as Vu and Tran (2019) showed that the recorders can record gibbon calls at a distance up to about 600-700 m in Cat Tien National Park.…”

Section: Recording Gibbon Callsmentioning

confidence: 99%

“…At each cell, a mobile smartphone was placed at a recording post near the center of the cell (Figure 2). Specifically, in 2019, within 200 m of the center of the cell, we chose a peak or ridge to place the phone to maximize the area the smartphone would survey and record (Vu & Doherty, 2021). We attached the smartphones to the tree trunks at a height from 1 to 2 m. In 2022, 14 recording posts in the northern part of the nature reserve were excluded from sampling because no detections were recorded in 2019 and those posts are located in a separate area (separated by a large river) that make gibbon colonization unlikely.…”

Section: Recording Gibbon Callsmentioning

confidence: 99%

“…Because of these data collection needs, the use of PAM provides a cost-effective means to collect occurrence data of gibbons. This approach was successfully implemented by deploying mobile smartphones to assess the occurrence of northern yellow-cheeked gibbons, Nomascus annamensis in Dakrong Nature Reserve in 2019 (Vu & Doherty, 2021), and smartphones are an inexpensive tool for wildlife acoustic monitoring.…”

Section: Introductionmentioning

confidence: 99%

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Passive acoustic monitoring using smartphones reveals an alarming gibbon decline in a protected area in the central Annamite Mountains, Vietnam

Vu,

Doherty,

T. Nguyen

et al. 2023

American J Primatol

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Monitoring populations is critical for understanding how they respond to anthropogenic disturbance and for management of protected areas. The use of passive acoustic monitoring can improve monitoring efforts as it allows for collection of data on vocal animals at spatial and temporal scales that are difficult using only human observers. In this study, we used a multiseason occupancy model to monitor occurrence, apparent extinction, and colonization probabilities of a northern yellow‐cheeked gibbon, Nomascus annamensis population with acoustic data collected from mobile smartphones in Dakrong Nature Reserve, Vietnam. Forty‐five sites were randomly selected for repeated surveys in 2019 and 2022. At each site, a mobile smartphone was attached to a tree and recorded sounds for 4.2 days and 3.89 days on average, in 2019 and 2022, respectively. We manually annotated spectrograms for the presence of gibbon calls, and we detected gibbons at 24 and 12 recording posts in 2019 and 2022, respectively. Estimated local apparent extinction from occupancy models was high with 67% of occupied sites in 2019 becoming unoccupied in 2022. Apparent colonization was low with ~25% of unoccupied sites in 2019 becoming occupied in 2022. As a result, the apparent occurrence probability declined from 0.58 in 2019 to 0.30 in 2022. If the absence of calls indicates that cells are unoccupied this would mean an alarming decline of the gibbon population in the nature reserve. We suggest that in the areas with high hunting pressure, monitoring intervals should be shortened to at least yearly. In addition, urgent actions, such as patrolling, or gun confiscation, should be implemented to conserve the gibbon populations in Dakrong Nature Reserve and other protected areas with the same management context.

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Manual Versus Semiautomated Bioacoustic Analysis Methods of Multiple Vocalizations in Tricolored Blackbird Colonies

Honig

Schackwitz

2023

Journal of Fish and Wildlife Management

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Bioacoustic monitoring can reveal aspects of animal behavior as many species vocalize in association with certain behaviors. Despite this, bioacoustics remain infrequently used to monitor animal behavior due to lack of knowledge of how vocalizations relate to behavior and the challenge of efficiently analyzing the large acoustic datasets necessary to capture relevant behaviors. Vocalizations and associated behaviors have been previously established for the colonial tricolored blackbird Agelaius tricolor, but efficient analysis of the acoustic data remains a challenge. Previous work with tricolored blackbird acoustic data relied on manually listening to recordings, which is not practical on large scales. Using software to automatically detect vocalizations of interest has potential to reduce analysis time. However, automated detection is prone to errors often caused by faint vocalizations, overlapping calls, and background noise. Thus, incorporating components of manual and automated analysis of acoustic datasets remains essential. To address these challenges, we deployed autonomous recording units at three tricolored blackbird colonies from 2019 to 2021 and analyzed acoustic data using a manual and a semi-automated analysis method. Specifically, we used tricolored blackbird male song, male chorus, female song, hatchling call, nestling call, and fledgling call to determine the approximate timing of breeding stages and number of breeding attempts, or pulses, for each colony. We found that using a semi-automated approach was more time efficient than manual analysis, while using comparable numbers of recordings and obtaining equivalent information from the colonies. The odds of correct detections of vocalizations using the semi-automated method were generally lower for fainter vocalizations and colonies with high background noise. Overall, the semi-automated approach had tolerable rates of recall, precision, false positives, and false negatives. Our methodology adds to a growing body of literature addressing acoustic analysis, especially for colonial species and where questions of breeding phenology are important.

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Using bioacoustics to monitor gibbons

Cited by 3 publications

References 23 publications

Using mobile smartphones and bioacoustics to monitor endangered bird species

Using mobile smartphones and bioacoustics to monitor endangered bird species

Passive acoustic monitoring using smartphones reveals an alarming gibbon decline in a protected area in the central Annamite Mountains, Vietnam

Manual Versus Semiautomated Bioacoustic Analysis Methods of Multiple Vocalizations in Tricolored Blackbird Colonies

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