William D. Halliday

Bowhead whales ( Balaena mysticetus ) are an endemic species to the Arctic Ocean and are highly reliant upon acoustic communication. Despite being one of the most thoroughly studied populations of bowhead whales, we still have a poor understanding of the calling behavior of Bering‐Chukchi‐Beaufort (BCB) bowhead whales. In order to address this knowledge gap, we extracted 2326 bowhead whale calls from passive acoustic recordings taken between 2018 and 2021 at eight bottom‐mounted hydrophone recording sites across the eastern Beaufort Sea and Amundsen Gulf. Using a random forest model, we classified eight distinct call categories based on 16 acoustic features with 86% accuracy. We present descriptive statistics for these different call categories, highlighting the most important acoustic features used in differentiating between them. By quantitatively describing these calls and defining the vocal repertoire of BCB bowhead whales, this study lays important groundwork for examining the acoustic ecology of this highly vocal marine species. These results provide a basis to test hypotheses regarding the association of various calls and behaviors in order to assess call function, as well as building an acoustic morphology database for future call detectors and dialect comparison with other bowhead whale populations.

In many species, acoustic communication is essential for successful reproduction, parental care, and predator defense. The plainfin midshipman, Porichthys notatus , is a soniferous toadfish that relies on acoustic communication, with nest‐guarding males emitting long, tonal “hums” to attract mates, and short “grunts” and “growls” to defend nests and offspring from competitors and predators in their intertidal breeding grounds. Although these three vocalizations are a critical part of this species' repertoire, we still know relatively little about how these fish modulate their vocal communication in the complex acoustic environment of the marine intertidal zone. In this study, we recorded plainfin midshipman vocalizations at two sites on Vancouver Island, British Columbia, Canada, in 2018 and 2020 to better understand how season and abiotic conditions influence the occurrence of hums, growls and grunts. Hum presence at both locations peaked in June, increased at night compared to daytime, and positively correlated with water depth (tidal height). Hums also fluctuated in accordance with the lunar cycle, with elevated call presence observed during the quarter moon and associated neap tide phases. Growls similarly varied with the lunar cycle, but less notably than hums while grunts did not clearly covary with the lunar cycle. Growls and grunts both increased with water depth and were produced at similar rates both during the day and night. Our study demonstrates that plainfin midshipman adjust their acoustic behavior to match natural environmental cycles, and that the lunar and tidal cycles are important factors affecting reproductive behavior in this vocal intertidal fish.

Ringed seals (Pusa hispida) in the Arctic face habitat loss from climate change, making monitoring critical for conservation. Passive acoustic monitoring provides essential data; however, large data volumes require automated analysis. We developed a ResNet-based detector for ringed seal barks in passive acoustic recordings. The detector achieved F1 scores above 0.90 on development data and held-out datasets from different locations and recording periods. In continuous recordings, it maintained high recall (>0.90), with lower precision (∼0.5) reflecting a trade-off between detecting most vocalizations and false positives from acoustically similar non-target sounds. The open-source detector supports large-scale bioacoustic monitoring.

Ringed seals ( Pusa hispida ) use sea ice year‐round in the Arctic as a platform for giving birth, raising young and moulting. Arctic ringed seal population assessments are typically conducted by aerial surveys flown in the spring, when many seals haul out. However, many factors can influence whether a seal is hauled out on the ice and available for detection. Understanding the environmental factors that impact ringed seal haul‐out behaviour will reduce bias in aerial surveys. We deployed camera traps near Ulukhaktok, Northwest Territories, Canada in mid‐May 2023, 2024 and 2025 facing open water leads in the sea ice to document haul‐out behaviour of ringed seals under varying weather conditions. We used generalized additive mixed models to analyse the presence/absence and number of ringed seals hauled out. We found that high temperatures (> −4.3°C), low wind speeds (< 20 km/h), and high barometric pressure systems (101.4–101.8 kPa) increased the probability and number of ringed seals hauling out. We also found that haul‐outs occurred at lower temperatures under conditions of low and moderate wind speeds, and that the number of seals hauled out increased at lower temperatures at low wind speeds. We identify specific ‘ideal weather’ parameters for aerial surveys, which will reduce availability bias when calculating density and abundance estimates.

Aim: The urgency for remote, reliable and scalable biodiversity monitoring amidst mounting human pressures on ecosystems has sparked worldwide interest in Passive Acoustic Monitoring (PAM), which can track life underwater and on land. However, we lack a unified methodology to report this sampling effort and a comprehensive overview of PAM coverage to gauge its potential as a global research and monitoring tool. To address this gap, we created the Worldwide Soundscapes project, a collaborative network and growing database comprising metadata from 416 datasets across all realms (terrestrial, marine, freshwater and subterranean).Location: Worldwide, 12,343 sites, all ecosystem types.Time Period: 1991 to present.Major Taxa Studied: All soniferous taxa.Methods: We synthesise sampling coverage across spatial, temporal and ecological scales using metadata describing sampling locations, deployment schedules, focal taxa and audio recording parameters. We explore global trends in biological, anthropogenic and geophysical sounds based on 168 selected recordings from 12 ecosystems across all realms.Results: Terrestrial sampling is spatially denser (46 sites per million square kilometre—Mkm²) than aquatic sampling (0.3 and 1.8 sites/Mkm² in oceans and fresh water) with only two subterranean datasets. Although diel and lunar cycles are well sampled across realms, only marine datasets (55%) comprehensively sample all seasons. Across the 12 ecosystems selected for exploring global acoustic trends, biological sounds showed contrasting diel patterns across ecosystems, declined with distance from the Equator, and were negatively correlated with anthropogenic sounds.Main Conclusions: PAM can inform macroecological studies as well as global conservation and phenology syntheses, but representation can be improved by expanding terrestrial taxonomic scope, sampling coverage in the high seas and subterranean ecosystems, and spatio‐temporal replication in freshwater habitats. Overall, this worldwide PAM network holds promise to support cross‐realm biodiversity research and monitoring efforts.

An analysis of ambient noise data collected from seven locations in the western Canadian Arctic at varying depths (30–350 m) during ice-free seasons over a period of five years (2018–2022) has been conducted. The measured noise level correlates well with wind speed after the removal of contaminated (sources other than wind) noise data. The characteristics of wind noise are predicted by fitting a multi-parameter empirical model to data. Results from the model are compared with existing empirical wind noise models and validated using data collected from one of the measurement locations.

A growing and increasingly globalised human population, requiring the movement of goods and commodities, is placing increasing demands on the maritime industry, resulting in a concurrent increase in global shipping activities. This has consequences for the marine environment, particularly for species vulnerable to the impacts of vessel traffic. For example, vessel collisions can result in sub‐lethal or fatal injuries for marine mammals, whilst vessel noise can cause acoustic masking that effectively reduces an animal's listening space, potentially impacting their communication, navigation and foraging capacity. While a number of parallel approaches to mapping collision risk to large whales have arisen, these methods vary in their focus, usually on either co‐occurrence, collision probability, or probability of mortality. However, little attention has been given to the implications of methodological choice and data selection on subsequent risk predictions. To assess differences between these approaches, we used a standardised input dataset comprised of telemetry‐point data from tagged bowhead whales, and satellite‐based Automated Identification System (AIS) data of spatial vessel movements covering the Davis‐Baffin Arctic Marine Area. We applied this data to eight different, previously published analyses for deriving areas of vessel risk. We found that the choice of risk mapping approach affected the location, and total area, identified as ‘high risk’, and that more computationally complex approaches did not necessarily equate to different predictions. There was considerable variation in the total area of ‘high risk’ predicted within each map (range = 20–42,246 km²). Synthesis and Applications. The results underscore the importance of methodological transparency, informed data selection and careful interpretation when predicting collision risk. We provide practical recommendations for enhancing transparency when predicting risk, and discuss choice of approach suitable for different situations or management applications. It is critical that managers and policy makers are aware of the implications of applying different approaches when interpreting risk evaluation outputs.

Humpback whale (Megaptera novaeangliae) nonsong vocalizations, or social calls, are much more poorly understood than humpback song. We examined humpback whale social calls from a foraging ground in southern British Columbia (BC) and developed a catalog for humpback social calls in BC. We tagged four humpback whales on the eastern edge of Swiftsure Bank, BC, in early September 2020, with a passive acoustic and movement tag. We manually classified 32 call types in our data set based on comparisons with published classifications of humpback social calls. Many of the calls identified in our data set had similar characteristics to calls from other locations. We also used two statistical classification methods, a cluster analysis and a random forest. The cluster analysis grouped 20 of these call types into four categories, and the random forest classifier was able to accurately classify all 20 call types 87.6% of the time. This study fills a geographical gap of humpback whale social calls on foraging grounds and is a first step towards categorizing the social calls of humpback whales in BC.

The urgency for remote, reliable, and scalable biodiversity monitoring amidst mounting human pressures on climate and ecosystems has sparked worldwide interest in Passive Acoustic Monitoring (PAM), but there has been no comprehensive overview of its coverage across realms. We present metadata from 358 datasets recorded since 1991 in and above land and water constituting the first global synthesis of sampling coverage across spatial, temporal, and ecological scales. We compiled summary statistics (sampling locations, deployment schedules, focal taxa, and recording parameters) and used eleven case studies to assess trends in biological, anthropogenic, and geophysical sounds. Terrestrial sampling is spatially denser (42 sites/M·km ² ) than aquatic sampling (0.2 and 1.3 sites/M·km ² in oceans and freshwater) with only one subterranean dataset. Although diel and lunar cycles are well-covered in all realms, only marine datasets (65%) comprehensively sample all seasons. Across realms, biological sounds show contrasting diel activity, while declining with distance from the equator and anthropogenic activity. PAM can thus inform phenology, macroecology, and conservation studies, but representation can be improved by widening terrestrial taxonomic breadth, expanding coverage in the high seas, and increasing spatio-temporal replication in freshwater habitats. Overall, PAM shows considerable promise to support global biodiversity monitoring efforts.