Killer Whales Research Articles

Killer whales in the Gulf of Mexico and North Atlantic off the Southeastern United States

Killer whales occur in the Gulf of Mexico (GoMex) and the North Atlantic, including off the southeastern United States (SEUS). Data from cetacean surveys during 1990 – 2021 and other sources were combined to assess killer whale biology, including spatial and temporal distribution, social structure, genetics, morphology, acoustics, and predatory behavior. GoMex records occurred predominantly in oceanic waters (>200 m) during spring and summer. SEUS records occurred primarily in winter and spring off the North Carolina region along the shelf-edge and deeper waters, and off the east coast of Florida. Photo-identification analysis of GoMex killer whales resulted in 49 individuals sighted up to seven times with sighting histories up to 26 years, and social analysis provided evidence of long-term relationships up to 16 years. The GoMex genetic samples revealed two mtDNA haplotypes, one of which does not match any outside the GoMex. Most GoMex whales had wide non-faint saddle patches and many had cookiecutter shark scars while no scars were noted on SEUS whales. Three groups recorded in the GoMex made few calls, but a group harassing sperm whales produced many. Cetaceans and tuna are known prey in the GoMex and SEUS, respectively. Directed studies of killer whales in the GoMex areas would be difficult to implement as this species is very rare. It is therefore important to pursue ongoing efforts to collect behavioral, acoustic and any biological samples that will contribute to improve our understanding of the biology and ecology of killer whales in tropical and subtropical regions.

Stranding of a Newborn False Killer Whale on Utila Island, Honduras

Stranding of a Newborn False Killer Whale on Utila Island, Honduras

Killer Whale Predation on a Giant Manta Ray (Mobula birostris), a Sicklefin Devil Ray (Mobula tarapacana) and a Tiger Shark (Galeocerdo cuvier) in the Southwest Indian Ocean

ABSTRACTKnowledge of killer whale (Orcinus orca) feeding ecology in tropical waters is scarce. In the southwest Indian Ocean, opportunistic sightings provide a valuable source of information to better understand their behaviour, diet and distribution. Here, we compile existing records of killer whale predation on elasmobranchs in the southwest Indian Ocean, including sightings of three undescribed prey species regionally: a giant manta ray (Mobula birostris), a sicklefin devil ray (Mobula tarapacana) and a tiger shark (Galeocerdo cuvier). Documenting such observations is important to increase knowledge on killer whale ecology in the tropics and the cascading impact they might have on prey populations.

Exploring novel North Water Polynya ecosystems under climate change

Climate change is rapidly reshaping species distributions in the Arctic, which could profoundly impact ecosystem structure and function. While considerable effort has focused on projecting future species distributions, assessing the impacts of range-shifting species on recipient communities and subsequent disruptions to food webs remains largely unstudied. Here, we address this gap by combining species distribution models and ecosystem models to explore the emergence of novel ecosystems in the North Water Polynya. The North Water Polynya is an open-water area between Greenland and Canada, surrounded by sea ice and one of the world’s most productive ocean ecosystems. Using existing literature and projections from species distribution models of four marine species, we develop six plausible future ecosystem scenarios for the North Water Polynya. These scenarios include changing biomass of primary producers, changing biomass and size structure of copepods, shifting abundances of forage fish species, and the establishment of killer whales. We find that the biomass of higher trophic levels show pronounced decreases in response to the decrease in pelagic primary producers, with polar bear biomass halving compared to present conditions. Changes in the copepod size structure has the largest impact on the entire ecosystem compared to the other novel ecosystem scenarios, suggesting a strong reliance of higher trophic levels on large, lipid-rich copepods. We further show that increasing capelin with a simultaneous decrease in Arctic cod biomass causes large decreases in the biomass of marine mammals such as polar bear, beluga and ringed seal. Finally, we show the establishment of killer whales as a key novel predator could have cascading top-down effects on the North Water Polynya ecosystem. The framework presented here provides an approach for exploring the emergence of novel ecosystems and highlights how climate change could disrupt a high Arctic ecosystem.

Are narwhals critical for the meat supply in East Greenland ?

In East Greenland, the recommendations for the closure of the narwhal (Monodon monoceros) hunt coincide with a pressing demand to continue hunting for meat to supply local communities. By analysing catch statistics and estimating average meat yields, the available meat from marine mammals, polar bears (Ursus maritimus), and muskox (Ovibos moschatus) in East Greenland can be assessed. On average, there was approximately 426 tonnes of meat available per year during this period. However, this quantity declined due to reduced catches of hooded seals (Cystophora cristata) and ringed seals (Phoca hispida) after 2007. This decline was somewhat offset by the inclusion of new species in the hunt, such as dolphins (Delphinidae), killer whales (Orcinus orca), and pilot whales (Globicephala melas). The average annual meat availability per inhabitant decreased from 150 kg before 2008 to 94 kg afterward. Narwhals consistently contributed approximately 5–6% of the total annual meat supply in Greenland over the observed period, which suggests that narwhal meat is not critical for the overall food supply. The inclusion of the need for meat in discussions surrounding sustainable harvest levels has been a point of controversy, particularly in cases where an urgent halt to hunting is needed.

A Review of Science and Conservation Management for the Cumberland Sound Beluga Population

For many centuries, belugas, or white whales (Delphinapterus leucas), have been a major source of subsistence and cultural identity for the Inuit living along the shores of Cumberland Sound, southeastern Baffin Island. During the late 1800s and first half of the twentieth century, the whales were also heavily exploited commercially for their oil and skins. By the late 1960s and early 1970s it had become clear that the beluga population was greatly reduced from its historical abundance, and efforts began to limit the harvest and monitor the population. The purposes of this paper are to (i) provide a synthesis of developments in Cumberland Sound beluga science and harvest management since 1980 and (ii) describe and discuss efforts to improve the conservation status of the beluga population. Despite large investments in research since the transition to co-management under the Nunavut Agreement, much uncertainty and disagreement remains. Best scientific estimates of current beluga numbers are in the range of 1000 – 1500, with no clear evidence of an increasing or decreasing trend. Officially reported annual landings of harvested whales for the Baffin Island community of Pangnirtung in recent years have ranged between 15 (1993) and 52 (2006), with an average of around 40 whales. Ongoing known or potential threats identified by hunters and scientists include overharvest, ecosystem (including climate-driven) change, interactions with commercial fisheries, predation by killer whales, and stress due to vessel noise. Addressing these issues will require continued research and improved relations between Inuit and the government. Fresh approaches are needed. Newly available analytical and procedural tools may help to overcome longstanding issues that are deeply embedded in cultural and philosophical differences.

Polyomavirus surveillance in cetaceans of Brazil: first detection of polyomavirus in Guiana dolphins (Sotalia guianensis)

Polyomaviruses (PyVs) are small double-stranded DNA viruses able to infect species across all vertebrate taxa. In cetaceans, PyVs have been reported only in short-beaked common dolphin (Delphinus delphis), common bottlenose dolphin (Tursiops truncatus) and killer whale (Orcinus orca). Herein, we surveyed PyV in 119 cetaceans (29 mysticetes and 90 odontocetes) stranded along the Brazilian coast, from 2002 to 2022, comprising 18 species. DNA extracted from the lungs was tested using a nested PCR targeting the major capsid protein gene of PyV. Polyomavirus was detected in lung samples of 1.7% (2/119) cetaceans: two juvenile female Guiana dolphins (Sotalia guianensis) stranded in Rio de Janeiro (Rio de Janeiro state) and Guriri (Espírito Santo state), in 2018. Both retrieved sequences were identical and presented 93.3% amino acid identity with Zetapolyomavirus delphini, suggesting a novel species. On histopathology, one of the PyV-positive individuals presented basophilic intranuclear inclusion bodies morphologically consistent with polyomavirus in the lungs. Other available tissues from both cases were PyV-PCR-negative; however, both individuals tested positive for Guiana dolphin morbillivirus. To our knowledge, this is the first report of PyV infection in cetaceans of the Southern Hemisphere and the first description of a co-infection with morbillivirus.

Continuous active sonar may not fix noise pollution of killer whale habitats

Although quieter, continuous active sonar still interferes too much with killer whale communication.

Behavioral responses of Bigg's and Southern Resident killer whales (Orcinus orca) to uncrewed aerial vehicle‐based breath sample collection

Behavioral responses of Bigg's and Southern Resident killer whales (<i>Orcinus orca</i>) to uncrewed aerial vehicle‐based breath sample collection

Respiratory Intervals and Swimming Speed as Remotely Sensed Health Metrics in Free-Ranging Killer Whales (Orcinus orca).

Respiratory rate (mean number of breaths per minute) and respiratory interval (mean time between breaths) can offer insight into a diving mammal's activity state, metabolic rate, behavior, and synchronization due to social cohesion. Also, respiratory rate can reflect an individual animal's health and has the potential to be an informative remotely assessed health metric for monitoring individual animal health in endangered whale species and populations such as southern resident killer whales (Orcinus orca). Using data collected from noninvasive, land-based theodolite tracking, we analyzed swimming speed and surfacing intervals (i.e., mean dive time or mean time between breaths) from 20,613 surfacings of 98 individuals from two populations of the fish-eating, resident killer whale ecotype, namely, one growing (northern resident) and one declining and endangered (southern resident) population. Focal animal sampling was used to measure behavior of individuals of known age and sex in various activity states. Our objective was to evaluate variability and generate normal ranges for respiratory intervals and swimming speeds for killer whales of the Northeast Pacific Ocean resident, fish-eating ecotype to identify baseline respiratory intervals. We found that median respiratory intervals for fish-eating killer whales were between 26 and 29 s for all activity states and that swimming speeds varied by activity state. Median swimming speeds were similar for foraging and traveling (1.6 and 1.7 m/s, respectively), but were significantly slower during resting (1.1 m/s) and social activity (1.3 m/s) states. Three southern resident killer whales in poor body condition (had body condition scores in the lowest 20th percentile of the population) swam at reduced speeds and had shorter median respiratory intervals than outwardly healthy whales of similar age and sex. Respiratory rates, respiratory intervals, and swimming speeds are valuable remotely sensed metrics of health for free-swimming killer whales, especially when combined with other metrics as is the standard in veterinary examinations.

Legacy persistent organic pollutants among multiple cetacean species in the Northwest Atlantic

The historical contamination of eastern Canadian shelf waters remains an ongoing concern, predominantly stemming from anthropogenic discharges in the Great Lakes region. Although legacy persistent organic pollutants (POPs) were banned decades ago, it remains unclear whether their concentrations have sufficiently decreased to safer levels in cetaceans that feed in the continental shelf waters of the northwestern Atlantic. This study compares polychlorinated biphenyl (PCB) and organochlorine pesticide (OC) accumulation in six cetacean species sampled in the Northwest Atlantic from 2015 to 2022. We assessed the influence of relative trophic level and foraging habitat preferences on POP accumulations among species using stable isotopes and fatty acids as dietary tracers. We further identified the species most susceptible to the effects of these contaminants. Killer whales (Orcinus orca) exhibited the highest PCB (∼100 mg/kg lw) and OC concentrations, followed by other odontocetes, with lowest concentrations in mysticetes. Stable isotope analysis revealed an unexpected lack of correlation between δ15N values and contaminant levels. However, there was a positive correlation between δ13C values and POP concentrations. Cetaceans foraging on pelagic prey species, as indicated by elevated proportions of the FA markers 22:1n11 and 20:1n9, had lower contaminant loads compared to cetaceans with benthic/coastal FA signatures. PCB and DDT (dichlorodiphenyltrichloroethane) concentrations are lower now in most cetacean species than in the 1980s and 1990s, likely due to regulatory measures restricting their production and use. Although current PCB concentrations for most species are under the thresholds for high risks of immune and reproductive failure, concentrations in killer whales exceed all established toxicity thresholds, underscoring the need for further action to reduce sources of these contaminants to the continental shelf waters of the northwestern Atlantic.

Functional data analysis to describe and classify southern resident killer whale calls

The Southern Resident Killer Whale (SRKW) is an endangered population of whales found in the northeast Pacific. They have a vocal dialect unique from other killer whales, having a repertoire of distinct stereotyped calls. A framework for distinguishing SRKW call types using the frequency traces of the amplitude ridges from their spectrograms (termed frequency ridges) is proposed. The first step is the extraction of these ridges of SRKW calls using an Sequential Monte Carlo approach. Next, they are converted into functional data using B-spline functions. They are analyzed with a functional principal component (FPC) analysis to characterise the intrinsic variability of frequency ridges within a call type. The FPCs are able to capture the general patterns in the frequency ridges of the different SRKW call types. The FPCs are also used as the basis for call classification. Using a cross-validation procedure to assess the robustness of the classification, this framework proves to be successful for classification with some call types having an F1-score ≥80%, but other calls less well discriminated. On balance, this approach showed reasonable performance given the small sample size available, and provides a useful contribution towards the development of a universal tool for call classification.

3D audio recording of complex underwater sound fields

In this study, we developed a method to capture underwater sound fields and reproduce them for human listeners, providing an immersive 3D auditory experience. We recorded the sound field with an array of four hydrophones arranged in a tetrahedral structure. The side length of the tetrahedron (around 70 cm) was a compromise between capturing accurately the low frequency pressure gradients and spatial aliasing effects at higher frequencies. Subsequently, we transformed the signals into the domain of spherical harmonics facilitating a representation as first-order Ambisonics that is independent of the recording. For playback on devices such as headphones or loudspeaker systems, we used established decoding routines that enhance the immersive audio experience with techniques such as parametric decoding and diffuse sound field equalization. During an expedition to northern Norway, we recorded the underwater soundscape in deep fjords with vocalizing killer whales and singing humpback whales. The resulting binaural renderings for headphones of these sound scenes are astonishing and sparked interest among scientist, artists and general public. This research also helps to enhance our understanding and perception of these intelligent marine mammals and their unique acoustic underwater world, ultimately aiding in better protecting them from noise pollution.

Auditory masking of tonal and conspecific signals by continuous active sonar, amplitude modulated noise, and Gaussian noise in killer whales (Orcinus orca).

Continuous active sonar is thought to mitigate severe acoustic impacts due to its lower sound pressure level compared to pulsed active sonar typically used by world navies. However, due to its almost continuous duty cycle, continuous active sonar could have a higher potential for auditory masking. Here, we evaluate the auditory masking potential of several noise types including a recording of continuous active sonar, amplitude modulated noise, and Gaussian noise, on signal detection in two killer whales. Signals were either a 1.5 kHz pure tone or a recording of a broadband burst-pulse killer whale call. For the 1.5 kHz tone, all noise types resulted in statistically significant masking, however, there was a release from masking of approximately 13 dB for the amplitude-modulated noise. When the killer whale call was the signal, the whales employed an off-frequency listening strategy where the whales were able to detect frequency components of the signal that did not directly overlap with the noise. However, this strategy was less useful for the continuous active sonar noise due to its broadband harmonic structure. Continuous active sonar has spectral features that considerably overlap with those of killer whale calls, making this type of noise an effective auditory masker.

Changes in Blood Analytes of Newly Captured Killer Whales (Orcinus orca): Influencing Factors

Changes in Blood Analytes of Newly Captured Killer Whales (Orcinus orca): Influencing Factors

Anthropogenic and killer whale (Orcinus orca) scarring on Pacific Coast Feeding Group gray whales (Eschrichtius robustus) in northwest Washington

Anthropogenic and killer whale (Orcinus orca) scarring on Pacific Coast Feeding Group gray whales (Eschrichtius robustus) in northwest Washington

Toxicogenomic assessment of hydroxylated metabolites of PBDEs on cetaceans: An in vitro study

Despite their ban, polybrominated diphenyl ethers (PBDEs) are frequently detected in various environmental compartments including marine and coastal ecosystems due to their persistence, bio-accumulative, high production volumes, and widespread use. One of the major concerns from PBDEs is the transformation products, such as hydroxylated polybrominated diphenyl ethers (OH-BDEs), which are more bioactive than the parent compounds. For example, 6-hydroxy-2,2′,4’,4-tetrabromodiphenyl ether (6-OH-BDE-47) is a typical metabolite of PBDEs and cause endocrine system disruption, developmental toxicity, and neurotoxicity in different species. Despite being widely detected in marine environments, investigations on the toxicological mechanisms of 6-OH-BDE-47 in cetaceans remain scarce. High concentrations of PBDEs accumulate in cetaceans due to the long lifespan and large fat reserve. The accumulated PBDEs have become the major source of OH-BDEs in cetaceans. We exposed immortalized fibroblast cell lines from the skin of pygmy killer whales (PKW-LWHT) and Indo-Pacific finless porpoises (FP-LWHT) to 6-OH-BDE-47 and analyzed changes in cellular function using transcriptomic data, along with enzymatic activity. Exposure to the body-relevant body burdens of 6-OH-BDE-47 (250 and 500 ng mL−1) significantly decreased cell viability. Differentially expressed genes in FP-LWHT exposed to 6-OH-BDE-47 were primarily enriched in the pathways associated with steroid metabolism. Total cholesterol was decreased by 6-OH-BDE-47, whereas low-density lipoprotein cholesterol and triglyceride levels were significantly increased in FP-LWHT cells. In contrast, glycolysis was the main enriched function of differentially expressed genes in PKW-LWHT cells exposed to 6-OH-BDE-47, and the enzyme activity of phosphofructokinase and hexokinase was upregulated. Thus, even though the cell viability of both cell lines from these two species was significantly suppressed by 6-OH-BDE-47, the cellular response or affected cellular function was different between the Pygmy killer whale and the Indo-Pacific Finless Porpoise, suggesting a diverse response towards OH-BDEs exposure.

First documented movement of wild killer whales (Orcinus orca) between Iceland and Norway

First documented movement of wild killer whales (<i>Orcinus orca</i>) between Iceland and Norway

A review of small cetacean hunts in Greenland

Seven odontocete species are targeted by hunters in Greenland. Beluga (Delphinapterus leucas) and narwhal (Monodon monoceros) are hunted under annual quotas. Atlantic white-sided dolphin (Lagenorhynchus acutus), white beaked dolphin (Lagenorhynchus albirostris), harbour porpoise (Phocoena phocoena), killer whale (Orcinus orca) and long-finned pilot whale (Globicephala melas) are hunted without quotas. From 1993–2023, 109, 645 small cetaceans have been recorded in the North Atlantic Marine Mammal Commission (NAMMCO) catch database as hunted in Greenland. The hunt follows the scientific advice in 3 out of 25 populations considered: the hunt is higher than the advice for 12 and there has been no assessment or advice for 10. Population trends are unknown for 14 populations, while numbers are stable or increasing in 6 and decreasing in 4. One population has been extirpated by hunting. Catches of all small cetaceans have increased since data records are available, including for narwhal and beluga since quotas have been in place. In some cases, insufficient monitoring and inaccurate reporting occur and there is a lack of data to assess struck and lost rates and times to death. Narwhals are experiencing significant declines in abundance due to hunting, particularly in East Greenland, where recovery may be compromised. To ensure the protection of small cetaceans in Greenland, management is required for all hunts, consistent with international conservation management recommendations. Measures should ensure sustainability, include stuck and lost and additional anthropogenic threats, be precautionary, based upon up-to-date knowledge of population status and trends and consider welfare aspects and recovery rates.

Males miss and females forgo: Auditory masking from vessel noise impairs foraging efficiency and success in killer whales.

Understanding how the environment mediates an organism's ability to meet basic survival requirements is a fundamental goal of ecology. Vessel noise is a global threat to marine ecosystems and is increasing in intensity and spatiotemporal extent due to growth in shipping coupled with physical changes to ocean soundscapes from ocean warming and acidification. Odontocetes rely on biosonar to forage, yet determining the consequences of vessel noise on foraging has been limited by the challenges of observing underwater foraging outcomes and measuring noise levels received by individuals. To address these challenges, we leveraged a unique acoustic and movement dataset from 25 animal-borne biologging tags temporarily attached to individuals from two populations of fish-eating killer whales (Orcinus orca) in highly transited coastal waters to (1) test for the effects of vessel noise on foraging behaviors-searching (slow-click echolocation), pursuit (buzzes), and capture and (2) investigate the mechanism of interference. For every 1 dB increase in maximum noise level, there was a 4% increase in the odds of searching for prey by both sexes, a 58% decrease in the odds of pursuit by females and a 12.5% decrease in the odds of prey capture by both sexes. Moreover, all but one deep (≥75 m) foraging attempt with noise ≥110 dB re 1 μPa (15-45 kHz band; n = 6 dives by n = 4 whales) resulted in failed prey capture. These responses are consistent with an auditory masking mechanism. Our findings demonstrate the effects of vessel noise across multiple phases of odontocete foraging, underscoring the importance of managing anthropogenic inputs into soundscapes to achieve conservation objectives for acoustically sensitive species. While the timescales for recovering depleted prey species may span decades, these findings suggest that complementary actions to reduce ocean noise in the short term offer a critical pathway for recovering odontocete foraging opportunities.