A comparison of three methods for estimating call densities of migrating bowhead whales using passive acoustic monitoring

Abstract

Various methods for estimating animal density from visual data, including distance sampling (DS) and spatially explicit capture-recapture (SECR), have recently been adapted for estimating call density using passive acoustic monitoring (PAM) data, e.g., recordings of animal calls. Here we summarize three methods available for passive acoustic density estimation: plot sampling, DS, and SECR. The first two require distances from the sensors to calling animals (which are obtained by triangulating calls matched among sensors), but SECR only requires matching (not localizing) calls among sensors. We compare via simulation what biases can arise when assumptions underlying these methods are violated. We use insights gleaned from the simulation to compare the performance of the methods when applied to a case study: bowhead whale call data collected from arrays of directional acoustic sensors at five sites in the Beaufort Sea during the fall migration 2007–2014. Call detections were manually extracted from the recordings by human observers simultaneously scanning spectrograms of recordings from a given site. The large discrepancies between estimates derived using SECR and the other two methods were likely caused primarily by the manual detection procedure leading to non-independent detections among sensors, while errors in estimated distances between detected calls and sensors also contributed to the observed patterns. Our study is among the first to provide a direct comparison of the three methods applied to PAM data and highlights the importance that all assumptions of an analysis method need to be met for correct inference.

Acoustic Characterization for The Feeding Activities of Haliotis discus Hannai

“…Passive acoustic technology is an acoustic method that can be used to detect the sound of animals in their natural environment [30]. In an underwater environment, a hydrophone can be used to monitor the sound actively produced by the target [31].…”

“…Therefore, passive acoustics has been used to monitor the behavior, distribution, and sound characteristics of shrimp, whales, manatees, etc. [30]. Smith et al [20,35] realized the analyses of the feeding sound of prawn and measured the feeding consumption through passive acoustics.…”