Killer Whales Research Articles

Activation of the xenobiotic metabolism and oxidative stress response by mixtures of organic pollutants extracted with in-tissue passive sampling from liver, kidney, brain and blubber of marine mammals.

We used in-tissue passive equilibrium sampling using the silicone polydimethylsiloxane (PDMS) to transfer chemical mixtures present in organs from marine mammals with lipid contents between 2.3 and 99%into in vitro bioassays. Tissues from five harbor porpoises (Phocoena phocoena), one harbor seal (Phoca vitulina) and one orca (Orcinus orca) from the North and Baltic Seas were sampled until thermodynamic equilibrium was reached. Mixture effects were quantified with cellular reporter gene bioassays targeting the activation of the aryl hydrocarbon receptor (AhR-CALUX), the peroxisome proliferator-activated receptor gamma (PPARγ-bla) and the oxidative stress response (AREc32), with parallel cytotoxicity measurements in all assays. After removing co-extracted lipids and other matrix residues with a non-destructive cleanup method (freeze-out of acetonitrile extract followed by a primary secondary amine sorbent extraction), the activation of the PPARγ and AREc32 were reduced by factors of on average 4.3±0.15 (n=22) and 2.5±0.23 (n=18), respectively, whereas the activation of the AhR remained largely unaltered: 1.1±0.075 (n=6). The liver extracts showed the highest activation, followed by the corresponding kidney and brain extracts, and the blubber extracts of the animals were the least active ones. The activation of the PPARγ by the liver extracts was reduced after cleanup by a factor of 11±0.26 (n=7) and the AREc32 activity by a factor of 1.9±0.32 (n=4). The blubber extracts did not activate the AhR up to concentrations where cytotoxicity occurred or up to an acceptable lipid volume fraction of 0.27% as derived from earlier work, whereas all liver extracts that had undergone cleanup activated the AhR. The developed in-tissue passive sampling approach allows a direct comparison of the bioassay responses between different tissues without further normalization and serves as a quantitative method suitable for biomonitoring of environmental biota samples.

Морские млекопитающие и парадигма щелчок–эхо–щелчок

Scientific publications on echolocation of trained marine mammals that contain the results of researches for proving or checking of existing click-echo-click echolocation paradigm are analyzed in this article. As a result of the analysis it is established out that only 90% of the measured intervals between packages of impulses exceed time of passing of a package to a target and back. It demanded an explanation and promotion of new hypotheses. Hypothesis of “forcing” the targets to vibration by marine mammals is proposed. Variants of forcing to vibration: click-responses, click-res(-click-)ponses, clicks-response. There are reasons to believe what this mode of echolocation use some species of toothed whales: killer whales, dolphins and white whales.
 In case of confirmation of a hypothesis of forcing to vibration during carrying out new experiments the using this operating mode of biolocators of marine mammals at creation of their technical analog can increase considerably the search productivity of hydroacoustic stations. Carrying out additional researches on verification of the assumption of lack of echo signals from targets during the work of a biolocator in operating mode of forcing to vibration is required.

Requirements and availability of prey for northeastern pacific southern resident killer whales.

The salmon-eating Southern Resident killer whale (SRKW) (Orcinus orca) population currently comprises only 73 individuals, and is listed as ‘endangered’ under the Species at Risk Act in Canada. Recent evidence suggests that the growth of this population may be limited by food resources, especially Chinook salmon (Oncorhynchus tshawytscha). We present spatio-temporal bioenergetics model for SRKW in the Salish Sea and the West Coast of Vancouver Island from 1979–2020 with the objective of evaluating how changes in the abundance, age-structure, and length-at-age of Chinook salmon populations has influenced the daily food consumption of the SRKW population. Our model showed that the SRKW population has been in energetic deficit for six of the last 40 years. Our results also suggested that the abundance of age-4 and age-5 Chinook salmon are significant predictors of energy intake for SRKW. We estimated that the annual consumption (April-October) of Chinook salmon by the whales between 1979 and 2020 ranged from 166,000 216,300. Over the past 40 years, the model estimated that the contribution in the predicted SRKW diet of Chinook salmon originating from the Columbia River has increased by about 34%, and decreased by about 15% for Chinook salmon stocks originating from Puget Sound. Overall, our study provides an overview of the requirements and availability of prey for SRKW over the last 40 years, while supporting the hypothesis that SRKW were limited by prey abundance in the study period.

A real-time data assimilative forecasting system for animal tracking.

Monitoring technologies now provide real‐time animal location information, which opens up the possibility of developing forecasting systems to fuse these data with movement models to predict future trajectories. State‐space modeling approaches are well established for retrospective location estimation and behavioral inference through state and parameter estimation. Here we use a state‐space model within a comprehensive data assimilative framework for probabilistic animal movement forecasting. Real‐time location information is combined with stochastic movement model predictions to provide forecasts of future animal locations and trajectories, as well as estimates of key behavioral parameters. Implementation uses ensemble‐based sequential Monte Carlo methods (a particle filter). We first apply the framework to an idealized case using a nondimensional animal movement model based on a continuous‐time random walk process. A set of numerical forecasting experiments demonstrates the workflow and key features, such as the online estimation of behavioral parameters using state augmentation, the use of potential functions for habitat preference, and the role of observation error and sampling frequency on forecast skill. For a realistic demonstration, we adapt the framework to short‐term forecasting of the endangered southern resident killer whale (SRKW) in the Salish Sea using visual sighting information wherein the potential function reflects historical habitat utilization of SRKW. We successfully estimate whale locations up to 2.5 h in advance with a moderate prediction error (<5 km), providing reasonable lead‐in time to mitigate vessel–whale interactions. It is argued that this forecasting framework can be used to synthesize diverse data types and improve animal movement models and behavioral understanding and has the potential to lead to important advances in movement ecology.

Killer whales of the Strait of Gibraltar, an endangered subpopulation showing a disruptive behavior

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Occurrence of long-finned pilot whales (Globicephala melas) and killer whales (Orcinus orca) in Icelandic coastal waters and their interspecific interactions

Long-finned pilot whales and killer whales are widely distributed across the North Atlantic, but few studies have reported their occurrence in Icelandic coastal waters. Here, we use sightings data from research platforms and whale watching tours in six regions of Iceland from 2007 to 2020 to show that the occurrence of long-finned pilot and killer whales varied with region and season. Killer whales were regularly encountered in the south of Iceland during summer and west of Iceland during winter/spring. Long-finned pilot whales were only seen during the summer and were most often encountered in the south, west, and northwest of Iceland. Long-finned pilot whale occurrence in the south of Iceland appeared to increase during the study period but killer whale occurrence showed no noticeable changes. Long-finned pilot whales were sighted often in the areas that were also frequented by killer whales and interspecific interactions were commonly observed when both species co-occurred. Interactions appeared to be antagonistic, with killer whales often avoiding long-finned pilot whales and sometimes fleeing at high speed, similar to what has been described elsewhere in the North Atlantic. In the majority of interactions observed (68%), killer whales avoided long-finned pilot whales by moving away, but in 28% avoidance was at high speed with both species porpoising. This variability in the type of behavioural responses indicates that interactions may be more complex than previously described. We discuss regional trends in long-finned pilot whale and killer whale sightings and potential drivers of the observed interactions.

Killer Whale (Orcinus orca) Pulsed Calls in the Eastern Canadian Arctic

&#x0D; Killer whales (Orcinus orca) produce a variety of acoustic signal types used for communication: clicks, whistles, and pulsed calls. Discrete pulsed calls are highly stereotyped, repetitive, and unique to individual pods found around the world. Discriminating amongst pod specific calls can help determine population structure in killer whales and is used to track pod movements around oceans. Killer whale presence in the Canadian Arctic has increased substantially, but we have limited understanding of their ecology, movements, and stock identity. Two autonomous passive acoustic monitoring (PAM) hydrophones were deployed in the waters of Eclipse Sound and Milne Inlet, in northern Baffin Island, Nunavut, Canada, in August and September 2017. Eleven killer whale pulsed call types, three multiphonic and eight monophonic, are proposed and described using manual whistle contour extraction and feature normalization. Automated detection of echolocation clicks between 20 and 48 kHz demonstrated little to no overlap between killer whale calls and echolocation presumed to be narwhal, which suggests that narwhal remain audibly inconspicuous when killer whales are present. Describing the acoustic repertoire of killer whales seasonally present in the Canadian Arctic will aid in understanding their acoustic behaviour, seasonal movements, and ecological impacts. The calls described here provide a basis for future acoustic comparisons across the North Atlantic and aid in characterizing killer whale demographics and ecology, particularly for pods making seasonal incursions into Arctic waters.

A redescription and re-evaluation ofKekenodon onamata(Mammalia: Cetacea), a late-surviving archaeocete from the Late Oligocene of New Zealand

AbstractStem cetaceans (archaeocetes) have a substantial Eocene fossil record but are largely absent since the Eocene–Oligocene boundary. Putative Oligocene archaeocetes are mostly represented by fragmentary denticulate teeth, making systematic classification difficult. The New Zealand species Kekenodon onamata (Wharekuri Greensand, Duntroonian local Stage, Chattian) is one of the most widely mentioned Oligocene archaeocetes and is the single-named species of the family Kekenodontidae. The holotype includes heterodont teeth in addition to cranial and post-cranial elements, and partial tympanoperiotics, with potential for a strong phylogenetic signal. Hitherto, the strikingly disparate Kekenodon onamata has been excluded from published phylogenetic analyses, with its affinities largely remaining speculative. Here, a detailed anatomical account allows a redescription of Kekenodon onamata, and a comprehensive phylogenetic analysis. The phylogenetic analysis shows Kekenodon onamata as the latest-surviving archaeocete, sister-taxon to the Neoceti. The large heterodont teeth with patterns of extensive enamel macrowear suggest Kekenodon onamata utilized a raptorial feeding strategy and hunted hard-boned prey, such as other marine mammals and penguins. Combined with an estimated body size of c. 8 m, Kekenodon onamata probably occupied an apex predator ecological niche similar to the modern killer whale.

How to Heal: What Killer Whales Teach Us about Love

How to Heal: What Killer Whales Teach Us about Love

A tale of two whales: applying digital imaging and 3D printing to cetacean research and education

Emerging technologies are changing how scientists and the public see and interact with cetacean specimens. As staff at a small, rural, marine science center, we employed LIDAR (light detection and ranging), x‐ray, computational tomography, and structured light scanning along with three‐dimensional (3D) printing to study and exhibit the remains of a 7.9‐m transient male killer whale (Orcinus orca) and a 22.4‐m female blue whale (Balaenoptera musculus). In collaboration with larger institutions, we applied these technologies to bone replication, skeletal articulation, soft‐tissue anatomical studies, and digital modeling to create high‐quality specimen replicas. These techniques surpass traditional modeling and restoration methods, and advance specimen‐associated research and documentation. In addition, 3D technology supports education and public awareness through in‐person and online exhibits and demonstrations. The decreasing cost and increasing appeal of advanced imaging can be used to enhance community engagement and the accessibility of science.

Insights sobre um encalhe em massa de falsas orcas (Pseudorca Crassidens Owen, 1846)

False killer whales (FKWs; Pseudorca crassidens) are found in deep waters of temperate and tropical oceans worldwide. This species is considered near threatened and global populations’ trends are unknown although there is evidence of decline of various populations. The mass stranding of cetaceans remains an intriguing event and often the cause(s) are unclear or poorly investigated. In Brazil, cetacean mass strandings have been recorded yet they have not been investigated. In this study, we aimed to report the epidemiologic features of a mass stranding event involving 30 live FKWs occurred in northeastern Brazil in 2013. Releasing attempts and posterior monitoring data indicated successful outcome for 24 of 30 FKWs. Postmortem pathologic investigations confirmed live-stranding stress response and intestinal (Bolbosoma sp.) and otic (Stenurus sp.) endoparasitism. Toxicologic analyzes detected high concentrations of total mercury in liver correlating with liver damage, as indicated by elevated transaminases. In this mass stranding, key factors were early notification, organizational and operational framework, trained and sufficient personnel, resources and equipment, government support, and strategy and decision making. These results underscore the benefits of a rapid marine mammal network response, the importance of integrative multidisciplinary investigations, and set baseline information for mass strandings of cetaceans in Brazil.

Movements and Diving Behavior of the Eastern North Pacific Offshore Killer Whale (Orcinus orca)

The Pacific Offshore killer whale population is currently listed as data deficient on the IUCN Red List and Threatened in Canada. The population is estimated at 300 individuals with a range extending from Southern California to the Aleutian Islands in Alaska. Only 157 encounters with this ecotype have been photo-documented between 1988 and 2014; consequently, movement and behavioral data are limited and restricted to areas commonly surveyed. To better understand movements, habitat use, and diving behavior, we deployed seven dart-attached satellite tags during two encounters with Offshores off California and one encounter off Washington State in 2013. Group size estimates were 6, 9, and 30 whales, respectively. Transmission durations ranged from 6.3 to 147.4 days providing a combined 2,469 location estimates. Whales tagged in Southern California travelled from 30.7°N to 59.3°N degrees latitude, covering a larger latitudinal range in 75 days than all previous sightings (33.5°N to 60.0°N). Within most of the California Current (southern extent of locations up to 48.5°N), Offshores typically used waters deeper than the 200 m isobath. As they approached the northern extent of the California Current and travelled into British Columbia and Alaska, locations were more common near or inside the 200 m isobath. Individuals tagged in the same group disassociated and re-associated within the tracking duration, with animals tagged together separating by as much 1,339 km. Two of the tags also reported summarized diving behavior, and tags captured 1,110 total dives with median dive depths of 41 m and 100 m for each tagged whale; the maximum dive depth was 480 m. Dives were typically short (median = 3.9 and 4.1 min respectively, max = 12.3). A comparison of dive depths and bathymetry suggests that whales typically dove to or near the seafloor in continental shelf habitat. Despite the small number of tag deployments, these data provide new information on social structure, individual ranges, diving behavior, and habitat use of this seldom encountered killer whale ecotype.

Blue whale heart rate immortalised in motion sensor trace

Scientists have been attaching motion sensors to penguins, whales and other marine animals for decades, recording their flipper and fluke beats and every twist and turn to learn about their extraordinary aquatic lifestyles. But could other details about these animals’ lives also be preserved in the jagged acceleration traces they recorded? ‘Last July, James Fahlbusch and I were going through tag data from a blue whale with a fine-toothed comb looking for night-time breathing behaviour’, says Max Czapanskiy from Stanford University, USA, when the duo stumbled across something unexpected. ‘We noticed repetitive, gentle noise in the accelerometry record during resting dives’, Czapanskiy recalls. And when the pair measured the time between the barely perceptible peaks in the noisy traces, they realised that it correlated with the period between each of the mighty beast's heart beats. Could the motion sensors have inadvertently measured the iconic creature's heart rate? Czapanskiy sent a quick screenshot to Paul Ponganis (Scripps Institution of Oceanography, USA) and Jeremy Goldbogen (Stanford University), who confirmed that his hunch could be correct. But, before they could be sure, the team needed to test their theory on killer whales at SeaWorld of California, USA, where they could simultaneously measure the animal's heart rate while recording its manoeuvres.Working with Todd Schmitt (SeaWorld) the team attached an ECG monitor and motion sensor to a killer whale and recorded the animal's heart beats and movements. Then, Czapanskiy and Ponganis analysed a 14 s portion of the killer whale's acceleration trace when the animal was stationary to search for any sign of a pulse. After months of patient investigation, the duo successfully revealed the soft throbbing motion as the animal's body gently recoiled in response to its heartbeat. And when they compared the movement trace with the killer whale's ECG record, they found the two corresponded perfectly. It is possible to extract heart rate records from the acceleration traces recorded by motion sensors when the animal is static, but could the team apply their novel technique to the manoeuvres of freely roaming wild whales?The researchers returned to the movement data collected by the motion sensor located behind the blue whale's flipper, close to its heart, as the animal dived to rest repeatedly at ∼20 m. Sure enough, the accelerations generated by the whale's mighty movements overwhelmed the gentle body jiggle produced by the animal's powerful heartbeat, so the team focused on 30 s to 2 min segments when the whale was clearly resting at the bottom of its dive. Czapanskiy and Ponganis were able to identify the gentle shuttling motion of the whale's body in response to its heartbeat, recording a heart rate ranging from 4 to 8 beats min−1, in agreement with the only ECG ever recorded from a blue whale. And when the team plotted the animal's heart rate over several dives, it increased gradually from ∼4.1 beats min−1 when the animal began its descent, to ∼8.3 beats min−1 as the whale returned to the surface.‘As accelerometer tags have been deployed on many cetacean species for multiple decades, this method may be applied to mine existing datasets and better understand how heart rate scales with body size and other biological factors’, says Czapanskiy. And the team suggests that the technique could help researchers and conservationists better understand the impact of human noise pollution on these sensitive animals. One thing is sure, there is already a treasure trove of heart rate measurements buried in the movement traces of whales, dolphins and other aquatic mammals waiting to be unearthed by scientists to learn more about the physiology of these depth-defying animals.

An accelerometer-derived ballistocardiogram method for detecting heart rate in free-ranging marine mammals.

ABSTRACTPhysio-logging methods, which use animal-borne devices to record physiological variables, are entering a new era driven by advances in sensor development. However, existing datasets collected with traditional bio-loggers, such as accelerometers, still contain untapped eco-physiological information. Here, we present a computational method for extracting heart rate from high-resolution accelerometer data using a ballistocardiogram. We validated our method with simultaneous accelerometer–electrocardiogram tag deployments in a controlled setting on a killer whale (Orcinus orca) and demonstrate the predictions correspond with previously observed cardiovascular patterns in a blue whale (Balaenoptera musculus), including the magnitude of apneic bradycardia and increase in heart rate prior to and during ascent. Our ballistocardiogram method may be applied to mine heart rates from previously collected accelerometery data and expand our understanding of comparative cardiovascular physiology.

Validation of quantitative fatty acid signature analysis for estimating the diet composition of free-ranging killer whales

Accurate diet estimates are necessary to assess trophic interactions and food web dynamics in ecosystems, particularly for apex predators like cetaceans, which can regulate entire food webs. Quantitative fatty acid analysis (QFASA) has been used to estimate the diets of marine predators in the last decade but has yet to be implemented on free-ranging cetaceans, from which typically only biopsy samples containing outer blubber are available, due to a lack of empirically determined calibration coefficients (CCs) that account for fatty acid (FA) metabolism. Here, we develop and validate QFASA for killer whales using full blubber from managed-care and free-ranging individuals. First, we compute full, inner, and outer blubber CCs from the FA signatures across the blubber layers of managed-care killer whales and their long-term diet items. We then run cross-validating simulations on the managed-care individuals to evaluate the accuracy of diet estimates by comparing full-depth and depth-specific estimates to true diets. Finally, we apply these approaches to subsistence-harvested killer whales from Greenland to test the utility of the method for free-ranging killer whales, particularly for the outer blubber. Accurate diet estimates for the managed-care killer whales were only achieved using killer whale-specific and blubber-layer-specific CCs. Modeled diets for the Greenlandic killer whales largely consisted of seals (75.9 ± 4.7%) and/or fish (20.4 ± 2.4%), mainly mackerel, which was consistent with stomach content data and limited literature on this population. Given the remote habitats and below surface feeding of most cetaceans, this newly developed cetacean-specific QFASA method, which can be applied to outer-layer biopsies, offers promise to provide a significant new understanding of diet dynamics of free-ranging odontocetes and perhaps other cetacean species throughout the world’s oceans.

Transcriptomes Suggest That Pinniped and Cetacean Brains Have a High Capacity for Aerobic Metabolism While Reducing Energy-Intensive Processes Such as Synaptic Transmission.

The mammalian brain is characterized by high energy expenditure and small energy reserves, making it dependent on continuous vascular oxygen and nutritional supply. The brain is therefore extremely vulnerable to hypoxia. While neurons of most terrestrial mammals suffer from irreversible damage after only short periods of hypoxia, neurons of the deep-diving hooded seal (Cystophora cristata) show a remarkable hypoxia-tolerance. To identify the molecular mechanisms underlying the intrinsic hypoxia-tolerance, we excised neurons from the visual cortices of hooded seals and mice (Mus musculus) by laser capture microdissection. A comparison of the neuronal transcriptomes suggests that, compared to mice, hooded seal neurons are endowed with an enhanced aerobic metabolic capacity, a reduced synaptic transmission and an elevated antioxidant defense. Publicly available whole-tissue brain transcriptomes of the bowhead whale (Balaena mysticetus), long-finned pilot whale (Globicephala melas), minke whale (Balaenoptera acutorostrata) and killer whale (Orcinus orca), supplemented with 2 newly sequenced long-finned pilot whales, suggest that, compared to cattle (Bos taurus), the cetacean brain also displays elevated aerobic capacity and reduced synaptic transmission. We conclude that the brain energy balance of diving mammals is preserved during diving, due to reduced synaptic transmission that limits energy expenditure, while the elevated aerobic capacity allows efficient use of oxygen to restore energy balance during surfacing between dives.

Echolocation click discrimination for three killer whale ecotypes in the Northeastern Pacific.

Three killer whale ecotypes are found in the Northeastern Pacific: residents, transients, and offshores. These ecotypes can be discriminated in passive acoustic data based on distinct pulsed call repertoires. Killer whale acoustic encounters for which ecotypes were assigned based on pulsed call matching were used to characterize the ecotype-specific echolocation clicks. Recordings were made using seafloor-mounted sensors at shallow (∼120 m) and deep (∼1400 m) monitoring locations off the coast of Washington state. All ecotypes' echolocation clicks were characterized by energy peaks between 12 and 19 kHz, however, resident clicks featured sub peaks at 13.7 and 18.8 kHz, while offshore clicks had a single peak at 14.3 kHz. Transient clicks were rare and were characterized by lower peak frequencies (12.8 kHz). Modal inter-click intervals (ICIs) were consistent but indistinguishable for resident and offshore killer whale encounters at the shallow site (0.21-0.22 s). Offshore ICIs were longer and more variable at the deep site, and no modal ICI was apparent for the transient ecotype. Resident and offshore killer whale ecotype may be identified and distinguished in large passive acoustic datasets based on properties of their echolocation clicks, however, transient echolocation may be unsuitable in isolation as a cue for monitoring applications.

Ecojustice Poetry in The BreakBeat Poets Anthologies

Ecological modes of thinking and an awareness of environmental (in)justice are becoming increasingly pronounced in the ethics and aesthetics of hip hop. One area in which the culture’s growing interest in ecology as practice and metaphor is particularly visible is hip hop poetry’s turn to ecojustice, or an intersectional concern with social and environmental justice, liberation, diversity, and sustainability. This article examines selected works from the first two volumes of anthologies published by Haymarket Books as part of their BreakBeat Poets series, focusing on three ecojustice-oriented poems that address animal rights, (un)natural disasters, and gentrification. Their authors–all Black women– draw from African American history and culture to illuminate the intertwined ideological, political, and economic dimensions of some of the most pressing humanitarian and environmental crises of today. Samantha Thornhill’s “Ode to a Killer Whale” takes the form of a poetic monologue by the fictional character of Kunta Kinte, revealing similarities between human and animal subjugation and inscribing animal liberation in the Black revolutionary tradition. Candace G. Wiley’s “Parcel Map for the County Assessor” re-members and re-creates a culture of place that permeated the speaker’s countryside childhood to present the larger-than-human cost of rural gentrification. Finally, Mariahadessa Ekere Tallie’s “Global Warming Blues” juxtaposes the personal and the elemental dimensions of climate change in a blues remix that advocates for ecojustice for the disenfranchised.

Bowhead whales and whaling in the central and eastern Canadian Arctic, 1970-2021

The history of bowhead whaling and hunt management in the eastern and central Canadian Arctic is reviewed. Subsistence hunting of bowhead whales by Inuit resumed in the 1990s under co-management arrangements that were part of land-claims settlement agreements. Removals by whaling in both Canada and Greenland have been accounted for in IWC Scientific Committee assessments of the Eastern Canada–West Greenland (EC-WG) stock, but Canada, having withdrawn from IWC membership in 1982, has no legal obligation to consider IWC management advice. From 1994-2021 the total reported catch of bowheads in the central and eastern Canadian Arctic was 39 (not including struck-and-lost whales or whales that died from incidental entanglement in fishing gear). Sixteen different communities, most of which had a long history of bowhead whaling prior to the arrival of commercial whalers, took at least one bowhead over that 27-year period. More than half of the recent catches have been by the communities of Igloolik, Sanijarak, Naujaat and Coral Harbour, all in the Foxe Basin–Repulse Bay–northern Hudson Bay region where at least occasional hunting of bowheads by local people had persisted until well into the 1970s. Greenland’s reported landed catches totaled from 2009-2015, with no successful hunts reported since 2015. Well over a third of the whales landed by both countries combined have been mature females, the most valuable class in terms of potential for population increase. Several factors in addition to hunting and entanglement in fishing gear are likely affecting EC-WG bowheads, including increased exposure to killer whale predation (linked to the massive reduction in sea ice) and other changes in ecological conditions driven primarily by climate change (e.g. more industrial activity, more vessel traffic, more noise). Recent analyses suggest the EC-WG stock of bowheads has grown considerably since the end of commercial whaling, with best estimates of current abundance in the range of 6000-7000 individuals. Even though the population appears capable of sustaining present levels of removal and disturbance, it is important for monitoring efforts to continue in both Canada and Greenland, with regular Indigenous participation. Local observations and traditional knowledge can be valuable sources of information on animal health, behaviour and phenology.

Discriminating and classifying odontocete echolocation clicks in the Hawaiian Islands using machine learning methods.

Passive acoustic monitoring (PAM) has proven a powerful tool for the study of marine mammals, allowing for documentation of biologically relevant factors such as movement patterns or animal behaviors while remaining largely non-invasive and cost effective. From 2008–2019, a set of PAM recordings covering the frequency band of most toothed whale (odontocete) echolocation clicks were collected at sites off the islands of Hawaiʻi, Kauaʻi, and Pearl and Hermes Reef. However, due to the size of this dataset and the complexity of species-level acoustic classification, multi-year, multi-species analyses had not yet been completed. This study shows how a machine learning toolkit can effectively mitigate this problem by detecting and classifying echolocation clicks using a combination of unsupervised clustering methods and human-mediated analyses. Using these methods, it was possible to distill ten unique echolocation click ‘types’ attributable to regional odontocetes at the genus or species level. In one case, auxiliary sightings and recordings were used to attribute a new click type to the rough-toothed dolphin, Steno bredanensis. Types defined by clustering were then used as input classes in a neural-network based classifier, which was trained, tested, and evaluated on 5-minute binned data segments. Network precision was variable, with lower precision occurring most notably for false killer whales, Pseudorca crassidens, across all sites (35–76%). However, accuracy and recall were high (>96% and >75%, respectively) in all cases except for one type of short-finned pilot whale, Globicephala macrorhynchus, call class at Kauaʻi and Pearl and Hermes Reef (recall >66%). These results emphasize the utility of machine learning in analysis of large PAM datasets. The classifier and timeseries developed here will facilitate further analyses of spatiotemporal patterns of included toothed whales. Broader application of these methods may improve the efficiency of global multi-species PAM data processing for echolocation clicks, which is needed as these datasets continue to grow.