Identifying and predicting occurrence and abundance of a vocal animal species based on individually specific calls

Abstract

Passive acoustic monitoring (PAM) offers opportunities to collect data on the occurrence of vocal species for long periods of time, at multiple locations, and under a range of environmental conditions. Some species emit individually distinctive calls, including bottlenose dolphins (Tursiops truncatus) that produce signature whistles. Our study used PAM to determine the seasonal occurrence of bottlenose dolphins and utilized individually specific signature whistles to (1) track individuals spatially and temporally, (2) assess site fidelity off Maryland (MD), USA, (3) estimate the minimum abundance of dolphins in the study area, and (4) develop a dynamic habitat‐based relative abundance model applicable as a real‐time dolphin relative abundance prediction tool. Acoustic recorders were deployed at two sites offshore of Ocean City, MD, and at one site in the upper Chesapeake Bay, MD. Acoustic recordings from 2016 to 2018 were analyzed for signature whistles, and re‐occurrences of individual whistles were identified using a combination of machine learning and manual verification. A habitat‐based density model was created using the number of signature whistles combined with environmental conditions. A total of 1518 unique signature whistles were identified offshore of Maryland and in the upper Chesapeake Bay. There were 184 re‐occurrences of 142 whistles, with a mean of 135 d between re‐occurrences (range = 1–681 d). These repeated detections of the same individuals occurred most frequently at the site near Ocean City, MD, indicating the highest site fidelity. Re‐occurrences were recorded among all three sites, indicating movement of dolphins between the Chesapeake Bay and off the Atlantic coast of Maryland. The weekly number of individual dolphins detected off the Atlantic coast was significantly related to two environmental variables: sea surface temperature and chlorophyll a concentration. This habitat model could be used to predict relative dolphin abundance offshore of Maryland and inform management within the region, including in relation to offshore wind energy development and other stakeholders.

Modern technologies and integrated observing systems are “instrumental” to fisheries oceanography: A brief history of ocean data collection

“…Passive acoustic systems do not transmit a sound source but use hydrophones to receive sounds made from animals, humans, or natural processes (e.g., wind, precipitation, seismics, and underwater volcanic eruptions). They can identify individual or groups of marine mammals, fish, and invertebrates to species and even recognize individual cetaceans (Bailey et al, 2021).…”

Possible occurrence of contact calls in all‐male groups of free‐ranging beluga whales

“…Coupled with photo‐identification methods (e.g., Chernetsky & Krasnova, 2018), acoustic studies offer a good opportunity for a long‐term monitoring of belugas' seasonal occurrence, abundance, and site fidelity, as well as for investigating their social organization, based on the association of their vocal signatures. Such studies are already underway for bottlenose dolphin populations (Bailey et al, 2021; Logominova & Agafonov, 2021), showing the potential for the monitoring of other vocally active species with identity calls.…”

Automated acoustic detection of river herring (Alewife and Blueback Herring) spawning activity

“…Passive acoustic monitoring (PAM) and automatic detection of auditory signals and cues have been used to study the ecology and behavior of animals across taxa (recent examples in birds: Campos‐Cerqueira et al 2021, Dickerson et al 2022; frogs: Lapp et al 2021; mammals: Bailey et al 2021, Law et al 2021, Madhusudhana et al 2021, Palacios et al 2021), including fish (Gannon 2008; Luczkovich et al 2008). However, despite the imperiled status of many North American fishes (Jelks et al 2008) and the need for monitoring programs (river herring: ASMFC 2012, Hare et al 2021), these methods have rarely been applied to fish species in this region.…”