# Continuous Audio‐Visual Sensor Monitoring Is More Effective Than Human Observers for Detecting Moor Macaques

## TL;DR

Audio-visual sensors like camera traps and acoustic monitoring are more effective than human observers for tracking moor macaques in tropical forests.

## Contribution

This study demonstrates that combining audio-visual sensors improves primate detection in dense forests compared to traditional human surveys.

## Key findings

- Camera traps and passive acoustic monitoring outperformed human point transects in detecting moor macaques.
- Combining both sensor methods achieved the highest detectability (p = 0.87 ± 0.05).
- Sensors surpassed human surveys after two days of monitoring in tropical forests.

## Abstract

The number of species threatened with extinction is continuously increasing, underscoring the need for reliable population estimates to develop effective conservation plans. The ability to confirm a species' presence during surveys (i.e., detectability) is central for population estimates. While audio‐visual sensors, like camera traps and passive acoustic monitoring (PAM), have emerged as valuable tools for monitoring primates, few studies have systematically compared their detectability, particularly in dense forests with limited visibility and for elusive species. Here, we compared 40‐days continuous monitoring with audio‐visual sensor (camera traps, N = 19; PAM, N = 7) versus human‐based point transects with three survey visits (N = 20) on wild moor macaques (Macaca maura) in two different habitats: forest (N = 10) and open areas (N = 10). Using occupancy models to compare the detection probability (p), we found that camera traps (p = 0.63 ± 0.04) and PAM (p = 0.79 ± 0.08) outperformed point transects (p = 0.33 ± 0.07), regardless of habitat type. After equalizing survey time between methods, we found that detections were greater on point transects in surveys shorter than 1 day, but camera traps and PAM equalized their performance with two survey days (p‐value < 0.05). Notably, combining both audio‐visual sensors yielded the highest detectability (p = 0.87 ± 0.05). These results highlight the effectiveness of audio‐visual sensors and support multi‐method approaches for monitoring primates in tropical forests. Overall, this research contributes to designing more effective monitoring protocols for primate species, which are essential for planning conservation strategies.

Camera traps and PAM outperformed human transects in detecting moor macaques: sensors overcame point transect detectability after 2 days survey. Combining both audio‐visual methods achieved highest detectability, supporting audio‐visual sensors as essential tools for primate monitoring in tropical forests.

Camera traps and acoustic monitoring over 40 days detected moor macaques more effectively than 3‐visit human surveys, with both sensor methods showing similar detectability.Under 1‐day surveys, human point transects detected moor macaques better than audio‐visual sensors. Beyond 2 days, sensors exponentially increased detectability, surpassing transects after 15 days.Combining camera traps and PAM maximized moor macaque detectability. Results support using both methods for primate surveys in tropical forests, confirming audio‐visual sensors as a key conservation tool.

Camera traps and acoustic monitoring over 40 days detected moor macaques more effectively than 3‐visit human surveys, with both sensor methods showing similar detectability.

Under 1‐day surveys, human point transects detected moor macaques better than audio‐visual sensors. Beyond 2 days, sensors exponentially increased detectability, surpassing transects after 15 days.

Combining camera traps and PAM maximized moor macaque detectability. Results support using both methods for primate surveys in tropical forests, confirming audio‐visual sensors as a key conservation tool.