Aude F. Pacini

Hawaiian monk seals (HMS; Neomonachus schauinslandi ) are endemic and endangered with a population of approximately 1600 individuals. While research has provided extensive information on HMS biology, movements and population ecology, its underwater vocal behaviour remains largely undocumented, with previous descriptions limited to two individuals in human care. To broaden our understanding of sound production in free-ranging seals, we deployed passive acoustic recorders at five sites across the Hawaiian archipelago. From >4500 h of recordings, we manually detected and classified >23 000 underwater vocalizations. A discriminant function analysis of 10 call types yielded an average correct classification rate of 63%. We identified 25 call types, including five published elemental calls and 20 novel calls. Nineteen of the novel call types were combinational calls—an undocumented communication strategy in pinnipeds. The novel Whine , captured via biologging tag- and citizen-scientist videos, provided a rare example of context-specific call use in pinnipeds. Vocalizations were low frequency (<1 kHz), short–medium duration (<7 s), with 66% occurring in bouts. Calls were detected throughout the day at three of five sites, with peaks at night and late afternoon. These findings establish a baseline for HMS vocal behaviour and emphasize the importance of acoustic communication in future research and conservation efforts.

Diving is one of the most important behaviors undertaken by marine mammals. Pilot whales (Globicephala spp.) are oceanic dolphins that regularly forage at extreme depths (∼600–1000 m) and maintain body sizes similar to beaked whales. They are also listed as data deficient, with little known about their population dynamics. To help fill this knowledge gap, we estimated their energetic demands through a combination of multiple data streams (e.g. unoccupied aerial systems photogrammetry, high-resolution accelerometry tag data, stomach content analysis and long-duration dive data from satellite tags) from short-finned pilot whales (Globicephala macrorhynchus) in Hawaiian waters. We estimated and compared pilot whale field metabolic rates from breathing frequency against a more granular cost of transport method developed from morphometrics and swimming kinematics, finding that these methods gave similar estimates of energetic expenditure during foraging dives. We then combined expenditure and intake estimates into an exploratory model of daily net energetic balance. Using an estimate of prey size derived from squid beaks collected from a stranded animal, we found that an average of 142±59.8 squid day−1 (52,000±21,800 squid year−1) is enough for an average adult short-finned pilot whale to reach a neutral net energetic balance. This species has an estimated population abundance of ∼8000 individuals in Hawaiian waters, suggesting that the population as a whole would require 416±175 million squid (at an average of 559±126 kJ squid−1) or approximately 88,000±37,000 tonnes of squid annually, assuming similar energetic requirements for each animal.

Spinner dolphins ( Stenella longirostris subsp.) in Hawaiʻi face the highest documented human activity exposure rates of any dolphin species worldwide, raising concerns about long‐term impacts. Fundamental to any appropriate management action for a protected species is the availability of reliable information on their abundance and distribution. Currently, abundance estimates are only available for one of the six designated stocks of spinner dolphins in Hawaiʻi. To address this information gap, small‐boat line‐transect surveys for spinner dolphins were conducted around the island of Oʻahu between October 2020 and May 2022. A total of 73 survey days were achieved, resulting in 3098 km of transects surveyed around the Oʻahu coastline. We used a novel method utilizing opportunistically collected unoccupied aerial system data to assess dolphin availability at the surface. We also investigated the potential for responsive movement of animals, for which no evidence was found. Estimated abundance of spinner dolphins for Oʻahu was 594 animals (95% CI [360, 980], CV = 0.26). Our findings represent the first circum‐island abundance estimate of Oʻahu's spinner dolphins, allowing management to explore strategies aimed at minimizing human‐dolphin interactions in the region and assess long‐term impacts.

With increased focus on offshore wind (OSW) as a renewable energy resource in the United States and elsewhere, there are concerns about OSW impacts to wildlife, particularly birds and marine mammals. This study identifies technology gaps and technological research and development (R&D) priorities for monitoring marine mammals and birds for fixed and floating OSW. A synthesis of current monitoring technologies generated two databases (with over 100 technologies) that can be integrated in current technology repositories for renewable energy projects. Generally, the key technology R&D needs are similar for birds and marine mammals. The main exception is that some types of bird technologies are more likely to require direct integration with OSW infrastructure, whereas marine mammal systems tend to operate independently. Priorities to advance wildlife monitoring include improved early communication, harmonization of technologies and data collection for monitoring systems on OSW structures, battery/power access improvements, remote data transfer improvements, and advancements in automated collection and analysis of data. The successful integration of wildlife monitoring systems into OSW infrastructure and operations is dependent on remote access mechanisms for data collection, system maintenance, and data transfer, in order to minimize risks to worker safety in the offshore environment, as well as minimizing costs and disruption to normal operational activities. Application of the results of this study to prioritize and fund technology R&D will help to support statistically robust data collection and practicable integration of monitoring systems into OSW operations and infrastructure.

Sensitivity to the local underwater acoustic stimulation of the ventro-lateral head surface was investigated in a bottlenose dolphin (Tursiops truncatus). The stimuli were tone pip trains of carrier frequencies ranging from 32 to 128 kHz with a pip rate of 1 kHz. Auditory evoked potentials (the rate following responses) were recorded. For all the tested frequencies, a low-threshold region was revealed at the lateral side of the middle portion of the lower jaw. This result differed from that obtained in a beluga whale, Delphinapterus leucas (Popov et al., JASA 2016, 140: 2018) revealed a maximal sensitivity region next to the medial side of the middle portion of the lower jaw. The comparative analysis of these data and their extrapolation to all odontocetes in generally is discussed.

Sensitivity to the local underwater acoustic stimulation of the ventro-lateral head surface was investigated in a bottlenose dolphin (Tursiops truncatus). The stimuli were tone pip trains of carrier frequencies ranging from 32 to 128 kHz with a pip rate of 1 kHz. Auditory evoked potentials (the rate following responses) were recorded. For all the tested frequencies, a low-threshold region was revealed at the lateral side of the middle portion of the lower jaw. This result differed from that obtained in a beluga whale, Delphinapterus leucas (Popov et al., JASA 2016, 140: 2018) revealed a maximal sensitivity region next to the medial side of the middle portion of the lower jaw. The comparative analysis of these data and their extrapolation to all odontocetes in generally is discussed.

Interactions between marine mammals and fisheries have a biological and economic impact that is often detrimental to both fishermen and species of concern. False killer whale bycatch in the Hawaii longline fishery has exceeded the potential biological removal (PBR) triggering the designation of a take reduction team under the Marine Mammal Protection Act (MMPA). As an attempt to understand the importance of acoustic cues in depredation events, this study presents preliminary data looking at the echolocation ability of a false killer whale (Pseudorca crassidens) to detect a longline fishing hook at various distances. Using a go/no-go paradigm, the whale was trained to report the presence of the hook at distances varying in 50 cm increments. A total of 28 sessions of 25 trials each were collected and echolocation signals were recorded using a nine element acoustic array. Number of clicks, acoustic parameters, decision time and performance were recorded. The subject successfully reported the presence of the hook up to 6 m. This work presents evidence that false killer whales can easily detect fishing gear which could influence how they interact with longline fishery.

Blast fishing is an illegal and unsustainable practice that is often reported in Southeast Asia and Africa. Its impact on fish and reef-building corals is well documented, yet there is limited information on the effects on other larger species and near-shore predators. In recent years, several marine mammal strandings in the Philippines have coincided with underwater explosions associated with blast fishing. The goal of this study was to measure the hearing of stranded dolphins, including two spinner dolphins (Stenella longirostris) and two rough-toothed dolphins (Steno bredanensis), that were rehabilitated in Subic Bay at Ocean Adventure in cooperation with the Philippines Marine Mammal Stranding Network and Wildlife in Need. Hearing measurements were conducted using noninvasive auditory brain stem responses (ABRs). Test stimuli consisted of tone pips ranging from 8 to 128 kHz. The results indicated elevated thresholds and limited hearing range, including three individuals with no hearing response beyond 22.5 kHz. These results may indicate evidence of hearing loss associated with blast and related impulsive sound exposure.

Understanding the hearing of marine mammals has been a priority to quantify and mitigate the impact of anthropogenic sound on these apex predators. Yet our knowledge of cetacean hearing is still limited to a few dozen species, therefore compromising any attempt to design adaptive management strategies. The use of auditory evoked potentials allows scientists to rapidly and noninvasively obtain the hearing data of species rarely available in captivity. Unfortunately, many practical and ethical reasons still limit the availability of large whales, thus restricting the possibility to effectively ensure that anthropogenic sounds have minimum effects on these species. The example of a recent Blainville’s beaked whale (Mesoplodon densirostris) audiogram collected after a stranding indicated, for instance, very specialized hearing between 40 and 50 kHz, which corresponded to the frequency-modulated upsweep signals used by this species during echolocation. The methods used during a stranding event are presented along with the major difficulties that have slowed down the scientific community in measuring the audition of large whales and the potential value in obtaining such results when successful.