Killer Whales Orcinus Orca Research Articles

Cetacean fauna of the southern part of the Barents Sea in winter 2019–2023 under changing climate conditions

Biophysical changes occurring in Arctic marine ecosystems under the influence of climatic factors may affect cetaceans staying here. For this reason, the urgent task is to conduct regular monitoring of marine mammals in order to assess the state of their populations and preserve the biodiversity of species. We analyzed the results of ship-based surveys of marine mammals carried out by the Polar branch of VNIRO in January–March 2019–2023 in the south of the Barents Sea and compared them with the observation data of earlier years. As the studies have shown, the winter cetacean fauna is currently represented by six species of baleen Mysticeti and toothed Odontoceti whales. White-beaked dolphin Lagenorhynchus albirostris Gray, 1846 was the most abundant and widespread species among all cetaceans; however, since 2022 we have seen a decrease in both the number of observations and abundance of this species. Fin whale Balaenoptera physalus Linnaeus, 1758 and killer whale Orcinus orca Linnaeus, 1758 were regularly registered in the study area, while sightings of harbor porpoise Phocoena phocoena Linnaeus, 1758 and humpback whale Megaptera novaeangliae Borowski, 1781 were single. Comparative analysis of the obtained data with the materials of 2012–2013 revealed some changes in the cetacean fauna that occurred during the last decade. In the waters of the southern part of the Barents Sea, there began met species that had not been previously recorded in our surveys, first of all, minke whale Balaenoptera acutorostrata Lacépède, 1804 and humpback whale. The materials we collected expanded our understanding of cetaceans staying in the western sector of the Russian Arctic during the winter.

Further insights into killer whales Orcinus orca preying on white sharks Carcharodon carcharias in South Africa

Photography and video footage, captured by researchers and tourists on board two vessels, provided insights into the predation techniques employed by an adult male killer whale Orcinus orca in Mossel Bay, South Africa. The incapacitation of its prey, a juvenile white shark Carcharodon carcharias (∼2.5 m TL), followed by consumption of the liver, occurred within less than 2 minutes, highlighting the predator proficiency of the killer whale. Notably, another adult male killer whale, and constant traveling companion with the first, was observed approximately 100 m away and was not involved during the predation. The following day a second carcass of a different eviscerated white shark (3.55 m TL) washed ashore in the vicinity, indicating that at least two white sharks may have been killed during the interaction.

Determination of water balance maintenance in Orcinus orca and Tursiops truncatus using oxygen isotopes.

The secondary adaptation of Cetacea to a fully marine lifestyle raises the question of their ability to maintain their water balance in a hyperosmotic environment. Cetacea have access to four potential sources of water: surrounding salt oceanic water, dietary free water, metabolic water and inhaled water vapour to a lesser degree. Here, we measured the 18O/16O oxygen isotope ratio of blood plasma from 13 specimens belonging to two species of Cetacea raised under human care (four killer whales Orcinus orca, nine common bottlenose dolphins Tursiops truncatus) to investigate and quantify the contribution of preformed water (dietary free water, surrounding salt oceanic water) and metabolic water to Cetacea body water using a box-modelling approach. The oxygen isotope composition of Cetacea blood plasma indicates that dietary free water and metabolic water contribute to more than 90% of the total water input in weight for cetaceans, with the remaining 10% consisting of inhaled water vapour and surrounding water accidentally ingested or absorbed through the skin. Moreover, the contribution of metabolic water appears to be more important in organisms with a more lipid-rich diet. Beyond these physiological and conservation biology implications, this study opens up questions that need to be addressed, such as the applicability of the oxygen isotope composition of cetacean body fluids and skeletal elements as an environmental proxy of the oxygen isotope composition of present and past marine waters.

Novel aerial observations of a group of killer whales Orcinus orca in The Bahamas

Novel aerial observations of a group of killer whales Orcinus orca in The Bahamas

Differences in the Diet of Reproductively Isolated Ecotypes of Killer Whales (<i>Orcinus orca</i> Linnaeus, 1758) in the Seas of the Russian Far East

A systematic analysis of the species composition of the prey of killer whale Orcinus orca Linnaeus, 1758 was carried out. The results of observations of killer whales hunting for different types of prey and the data from an analysis of the contents of their stomachs were summarized; the species affiliation of the prey was compared with the affiliation of predators to the R- or T-type based on a genetic analysis. It has been shown that killer whales of the Far Eastern seas of Russia have a pronounced foraging specialization, which correlates with the haplotype of the mitochondrial DNA control region. Killer whales with the NT1 and GAT haplotypes previously described for mammal-eating T-type killer whales from the northeast Pacific (also called Bigg’s killer whales) have been observed preying on marine mammals but not on fish. Killer whales with the SR haplotype, previously described for fish-eating R-type killer whales from the northeastern Pacific, preyed only on fish. Two new T-type killer whale haplotypes have been discovered; animals with these haplotypes have been observed preying on large baleen whales. The importance of traditions and social learning in the differentiation of ecological niches in cetaceans has been noted. The specialization to hunt certain prey transmitted from mother to calves allows killer whales of different ecotypes to avoid food competition and acquire morphological and behavioral adaptations that facilitate hunting for a particular type of prey.

Collective decision‐making in aquatic mammals

ABSTRACTCollective decision‐making is an essential part of day‐to‐day life for group‐living animals. These decisions can be unshared (e.g. leadership) or shared (e.g. consensus).Aquatic mammals face particular challenges when making collective decisions, including a three‐dimensional habitat that can make group coordination and collective navigation a challenge.We systematically reviewed literature on decision‐making in non‐human mammals by examining the types of collective decisions observed and hypotheses used to structure analyses.Most of the current literature was centred around terrestrial species, particularly within primates and artiodactyls. There are no collective decision‐making studies on aquatic mammal species outside of cetaceans. Both unshared and shared decision‐making have been reported in whales and dolphins, with leadership found in killer whalesOrcinus orcaand bottlenose dolphinsTursiopssp.and consensus decisions in sperm whalesPhyseter macrocephalus.Five recommendations for decision‐making research include: 1) clearly delineating the temporal components of decision‐making, 2) standardising research to allow for comparisons, 3) considering both shared and unshared decision‐making, 4) analysing decision‐making across behavioural contexts, and 5) avoiding anthropomorphic terminology.Future studies of collective decision‐making will help us better understand how non‐human mammals overcome environmental and contextual challenges – particularly in the case of aquatic species such as cetaceans, which face challenges related to their aquatic environment and exhibit phenomena such as mass strandings.

Occurrence of killer whales Orcinus orca off the Commander Islands and Avacha Gulf from 2008�2021 and its relation to the sea otter Enhydra lutris population decline

Occurrence of killer whales Orcinus orca off the Commander Islands and Avacha Gulf from 2008�2021 and its relation to the sea otter Enhydra lutris population decline

Quantifying a stopover of killer whales preying on gray whales rounding the Alaska Peninsula

Predation by killer whales Orcinus orca on recovering populations of baleen whales is being increasingly reported, but there have been no direct quantitative assessments of its importance, for either the predators or prey. We used photographic mark-recapture and satellite telemetry to assess the abundance and behavior of killer whales gathering to feed on gray whale Eschrichtius robustus calves and juveniles that were migrating around the Alaska Peninsula into the Bering Sea. We quantitatively describe this aggregation as a stopover, used in May and early June 2003-2008 by at least 197 different killer whales. Estimates of average stopover duration (1.8-3.6 wk) and annual abundance (89-128 killer whales) were variable and correlated with annual gray whale calf production (404-1528 calves). In years with more gray whale calves, killer whales spent more time at this geographic pinch point where they could presumably access adequate prey. In years with fewer calves, more killer whales used the study area but remained for a shorter time, presumably searching more widely when calves were scarcer. The presence of killer whales increased through May into early June, when satellite tags tracked northerly movements into the Bering Sea, and as far as 1620 km into the Chukchi Sea, likely following migrating gray whales. These data indicate focused and prolonged predation by killer whales on a recovered population of baleen whales and provide the first evidence of the importance of such predation in structuring killer whale populations and influencing their dynamics.

From diatoms to killer whales: impacts of pink salmon on North Pacific ecosystems

In response to a climate regime shift in 1977 and general heating of the North Pacific Ocean, pink salmon Oncorhynchus gorbuscha abundance reached record highs during 2005-2021, comprising 70% of all Pacific salmon. Pink salmon are approximately 25 times more numerous in odd- than even-numbered calendar years in some major North Pacific ecosystems, a unique demographic pattern analogous to repeating whole ecosystem treatment-control experiments. We found compelling examples indicating that in odd years, predation by pink salmon can initiate pelagic trophic cascades by reducing herbivorous zooplankton abundance sufficiently that phytoplankton densities increase, with opposite patterns in even years. Widespread interspecific competition for common-pool prey resources can be dominated by pink salmon, as indicated by numerous biennial patterns in the diet, growth, survival, abundance, age-at-maturation, distribution, and/or phenology of ecologically, culturally, and economically important forage fishes, squid, Pacific salmon and steelhead trout Oncorhynchus spp., seabirds, humpback whales Megaptera novaeangliae, and endangered southern resident killer whales Orcinus orca. In aggregate, the evidence indicates that open-ocean marine carrying capacity in the northern North Pacific Ocean and Bering Sea can be mediated by top-down forcing by pink salmon and by ocean heating, and that large-scale hatchery production (~40% of the total adult and immature salmon biomass) likely has unintended consequences for wild salmon, including Chinook salmon O. tshawytscha, and many other marine species. Further investigation of the effects of pink salmon on other species will increase our knowledge of ecosystem function and the important role top-down forcing plays in the open ocean

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.

Interactions, injuries, and mortalities of killer whales (Orcinus orca): observed during fishing operations in Alaska: supplementary table 2

Interactions, injuries, and mortalities of killer whales (Orcinus orca): observed during fishing operations in Alaska: supplementary table 2

Interactions, injuries, and mortalities of killer whales (Orcinus orca): observed during fishing operations in Alaska: supplementary table 1

Interactions, injuries, and mortalities of killer whales (Orcinus orca): observed during fishing operations in Alaska: supplementary table 1

Interactions, injuries, and mortalities of killer whales (Orcinus orca): observed during fishing operations in Alaska: supplementary table 3

Interactions, injuries, and mortalities of killer whales (Orcinus orca): observed during fishing operations in Alaska: supplementary table 3

Implications of wind and vessel noise on the sound fields experienced by southern resident killer whales Orcinus orca in the Salish Sea

The soundscape of critical habitat for southern resident killer whale (SRKW) Orcinus orca in the Salish Sea, the waters around southern British Columbia, Canada, and northern Washington State, USA, is shaped by wind and wave noise as well as heavy commercial and recreational vessel traffic loads. First, we used recordings from 6 passive acoustic moorings to characterize the acoustic landscape experienced by SRKW in this region, focusing on the frequencies used for communication and echolocation. Mid-frequency wind noise was prevalent in winter sound fields, whereas higher-frequency noise levels associated with increased numbers of recreational vessels increased during summer. Commercial vessel presence was consistent, with acoustic inputs prevalent in the western part of the study area. The potential implications of these additions on SRKW acoustics use were then explored for the frequency band 1-40 kHz to represent communication calls and at 50 kHz to consider echolocation. The inputs of wind were extrapolated from modelled hourly wind speed measures and commercial shipping noise. The noise impact was expressed as a proportional reduction of communication and echolocation extent compared to maximum acoustic ranges at ‘minimum ambient’ levels, void of vessel and abiotic noise. The reductions calculated were substantial, with the presence and impact of vessel noise greater than wind-derived additions and the greatest impacts around shipping lanes. Impacts were found for SRKW foraging areas, with implications for group cohesion and feeding success. This interpretation of the influence of natural and vessel noise more clearly demonstrates the potential implications of altered soundscapes for SRKW.

Shifting phenology of an endangered apex predator mirrors changes in its favored prey

The timing, or phenology, of predator activity in relation to their prey is critical for survival and fitness, yet rarely quantified for marine species, even those of conservation concern. We use a large database of professional and crowd-sourced observations analyzed with hierarchical spline occupancy models to quantify seasonal variation in occurrence of an endangered apex predator, the southern resident killer whale (SRKW)Orcinus orca, in inland waters of the northeast Pacific Ocean. We find that timing of SRKW occurrence has shifted in their summer core habitat within the central Salish Sea: the day of year of peak occurrence probability shifted later at rates of 1-5 d yr-1over 2001-2017 (resulting in shifts of 17-85 d across this 17 yr time period). These shifts are consistent with shifts in their preferred prey, Fraser River Chinook salmonOncorhynchus tshawytscha, as the relative number of fish returning to spawn in the spring has declined compared to numbers returning in summer and fall. The shift in timing of fall/winter SRKW occurrence outside the summer core habitat, however, is not consistent with shifts in other prey populations (Chinook, cohoOncorhynchus kisutch, chumOncorhynchus ketasalmon) returning to nearby rivers. Our findings demonstrate the complexity of consumer phenological responses and highlight gaps in our understanding of links between management actions that affect resource phenology and consequences for organisms relying on those resources.

An Assessment of Commercial Fleet Applications of Management Measures in Clayoquot Sound, British Columbia, Canada, Aimed to Mitigate Whale-watching Impacts

The interactions between wildlife tourism operators and the animals that they rely on are complex. For commercial whale watching, the recognition of the potential disturbance from the vessels generates uncertainty regarding the effectiveness of management strategies for it to remain a "no-take" practice. This warrants further evaluation. In this study, we analyzed the activities of the whale-watching fleet in Tofino, Vancouver Island, British Columbia, Canada, to evaluate industry sustainability and its ability to meet legislated conservation objectives. Visual observations gave context to an analysis of the communications of the fleet, made using very high frequency (VHF) marine radio. Transcription of these communications demonstrated three main themes: whale location, whale "transfers" between operators, and encounter or "show" quality. Cumulative encounter times from the fleet far exceeded the 30-min limit recommended in the whale-watching guidelines. Killer whales (Orcinus orca) were subject to the longest periods of vessel presence, with an average time spent in active encounters of 4.21 ±1.96 hr. This extended to almost the full operating day if whales remained within a feasible traveling distance of Tofino. Humpback (Megaptera novaeangliae) and gray whale (Eschrichtius robustus) encounters also exceeded the suggested time limit by 2.40 ± 1.73 hr and 1.31 ± 1.07 hr, respectively. Increased education and the addition of spatial and temporal restrictions in management regimes could address the shortcomings of the current system to minimize potential disturbance to whales from commercial whale-watching encounters and facilitate sustainable industry practices.

Killer whale (Orcinus orca) depredation on longline groundfish fisheries in the northwestern Pacific

Killer whale (Orcinus orca) depredation on longline groundfish fisheries in the northwestern Pacific

Passive acoustic monitoring of killer whales (Orcinus orca) reveals year-round distribution and residency patterns in the Gulf of Alaska

Killer whales (Orcinus orca) are top predators throughout the world’s oceans. In the North Pacific, the species is divided into three ecotypes—resident (fish-eating), transient (mammal-eating), and offshore (largely shark-eating)—that are genetically and acoustically distinct and have unique roles in the marine ecosystem. In this study, we examined the year-round distribution of killer whales in the northern Gulf of Alaska from 2016 to 2020 using passive acoustic monitoring. We further described the daily acoustic residency patterns of three killer whale populations (southern Alaska residents, Gulf of Alaska transients, and AT1 transients) for one year of these data. Highest year-round acoustic presence occurred in Montague Strait, with strong seasonal patterns in Hinchinbrook Entrance and Resurrection Bay. Daily acoustic residency times for the southern Alaska residents paralleled seasonal distribution patterns. The majority of Gulf of Alaska transient detections occurred in Hinchinbrook Entrance in spring. The depleted AT1 transient killer whale population was most often identified in Montague Strait. Passive acoustic monitoring revealed that both resident and transient killer whales used these areas much more extensively than previously known and provided novel insights into high use locations and times for each population. These results may be driven by seasonal foraging opportunities and social factors and have management implications for this species.

Synchrony erodes spatial portfolios of an anadromous fish and alters availability for resource users.

Environmental forces can create spatially synchronous dynamics among nearby populations. However, increased climate variability, driven by anthropogenic climate change, will likely enhance synchrony among spatially disparate populations. Population synchrony may lead to greater fluctuations in abundance, but the consequences of population synchrony across multiple scales of biological organization, including impacts to putative competitors, dependent predators or human communities, are rarely considered in this context. Chinook salmon Oncorhynchus tshawytscha stocks distribute across the Northeast Pacific, creating spatially variable portfolios that support large ocean fisheries and marine mammal predators, such as killer whales Orcinus orca. We rely on a multi-population model that simulates Chinook salmon ocean distribution and abundance to understand spatial portfolios, or variability in abundance within and among ocean distribution regions, of Chinook salmon stocks across 17 ocean regions from Southeast Alaska to California. We found the expected positive correlation between the number of stocks in an ocean region and spatial portfolio strength; however, increased demographic synchrony eroded Chinook salmon spatial portfolios in the ocean. Moreover, we observed decreased resource availability within ocean fishery management jurisdictions but not within killer whale summer habitat. We found a strong portfolio effect across both Southern Resident and Northern Resident killer whale habitats that was relatively unaffected by increased demographic synchrony, likely a result of the large spatial area included in these habitats. However, within the areas of smaller fishing management jurisdictions we found a weakening of Chinook salmon portfolios and increased but inconsistent likelihood of low abundance years as demographic synchrony increased. We suggest that management and conservation actions that reduce spatial synchrony can enhance short-term ecosystem resilience by promoting the stabilizing effect multiple stocks have on aggregate Chinook salmon populations and overall resource availability.

Natural Entrapments of Killer Whales (Orcinus orca): A Review of Cases and Assessment of Intervention Techniques

Identifying mortality sources and mitigation solutions is crucial in species management and conservation. In killer whales (Orcinus orca), mortality events may pose a serious concern for the conservation of small discrete populations, especially if they involve entire groups. This study investigated 19 incidents involving 116 killer whales from a minimum of five populations becoming naturally entrapped in inshore areas of the North Pacific (n= 12) and North Atlantic (n= 7) oceans between 1949 and 2019. Here, we aim to provide an assessment of possible causal factors, lethality and human responses to these events. Site characteristics and group size identified three categories of entrapments. InCategory 1, nine cases involved small groups of killer whales (median = 5, range: 1–9) at sites characterized by severe geographic and food constraints. Four cases inCategory 2included larger groups (median= 14, range: 6–19) and entrapment sites with no obvious geographic constraints but at which man-made structures could have acted as deterrents. Five cases assigned toCategory 3involved lone, often young individuals settling in a restricted home range and engaging in interactions with people and boats. Overall, all or some of the killer whales swam out on their own after a mean of 36 d of entrapment (range: 1–172, SD = 51,n= 9 cases), died of nutritional/physiological stress after 58 d (range: 42–90, SD = 21,n= 3 cases) or of injury after ~5 years of daily interactions with boat traffic (n= 1 case). Indication of the killer whales' declining condition or being at risk of injury, and of poor habitat quality, led to the decision to intervene in seven cases where a variety of methods were used to guide or relocate remaining individuals back to open waters after 39 d (SD = 51, range = 8–150). Monitoring protocols, which aided in identifying entrapment situations, and intervention methods which enhanced the health and survival of entrapped killer whales, are discussed.