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Photo-identification Catalogue, Population Status, and Distribution of Bigg’s Killer Whales known from Coastal Waters of British Columbia, Canada.
Abstract
In British Columbia, Bigg’s (transient) killer whales have been opportunistically photo-identified for several decades. This report uses a 61-year archive of photo-identification data from 1958-2018 to provide information on the abundance and distribution of Bigg’s killer whales known from BC. In total, 766 unique individuals were identified in a total of 6277 encounters during this time period. To identify the subset of this population that is most likely to be impacted by human activity due to showing the most fidelity to coastal waters over time, we developed criteria based on rates of occurrence, both overall and during recent years. A total of 206 mature individuals that were alive in 2018 were encountered at least once since 2014 and were documented during at least seven years or 11 or more encounters during the study period. Their offspring and other inferred maternally related kin include an additional 143 individuals. This population subset of 349 individuals has grown at an observed average annual rate of 4.1% since 2012 due to relatively low mortality and the birth of over 100 calves during this time period. Identification images of the dorsal fins, saddle patches, and eyepatches of all of these individuals as well as calves born to date in 2019 are provided. Details on the birth years, sex, maternal ancestry, social cohesion, and distribution of these individuals are also provided, when known.
... The photo identification process of killer whales (Orcinus orca) has historically been manually completed [3,6]. The identification of individuals is reliant on a number of primary factors including dorsal fin shape and size, the shape and color of the saddle patch -a dorso-posterior and ventro-anterior flare -and any markings or scars to the body [19]. The process of building a complete population overview is difficult, time consuming, expensive, and opportunistic, as it is often unclear where the individuals of the population are at any given time, and their overlap with locations of the photographers leads to a dataset which displays the long-tailed effect [23], where a few individuals are photographed many times. ...
... These data collection constraints and effects hold true for the Bigg's killer whale population, located in the northeastern Pacific Ocean. Field research began on this population in the 1970's and by 2018 766 individuals had been identified [19]. Due to the opportunistic nature of the data collection of these individuals, initial attempts at automating the identification process and addressing this imbalanced dataset focused on the 100 most commonly seen individuals out of the 367 living individuals between 2011 and 2017 [2] and achieved an accuracy of 92.5% with 97.2% top-3 unweighted accuracy (TUA). ...
... The evolution of the appearance of the animal plays a large role in its identification. Photos of each age class of an individual are important as the they progress into adulthood, and identification photos of the individuals in the earlier phases of life are particularly important as the body changes quickly [19]. The first issue largely describes the open set problem [8,1,17], while the second one can be mitigated with data analysis and management. ...
Machine-assisted photo identification processes require significant amounts of data for each member of a population of interest but offer the possibility to alleviate a significant amount of manual effort. Gathering such data is time consuming and opportunistic, leading to imbalanced datasets ill-suited for traditional machine (deep) learning efforts. Incomplete classifiers, trained on a subset of classes in a population, can be initially useful to identify the most commonly seen individuals. This study investigates the use of incomplete classifiers trained on a subset of often-observed individual killer whales to generate latent space representations of the larger population containing unseen individuals. These semantically relevant representations are subsequently clustered to investigate the efficacy of this method as a secondary identification mechanism. This method proves to be robust to a significant amount of noise while being able to isolate individuals unknown to the classifier when applying limited expert knowledge to the approximate size of the population.
... Photo-identification of killer whales was analyzed from photographs opportunistically taken from NOAA vessels or from small boats launched from the larger vessel to pursue groups of animals. We relied on the unique markings and the shapes of the dorsal fin, saddle patch, and postocular patches to identify individual killer whales (Dahlheim, 1997;Olson & Gerrodette, 2008), and compared them to published and unpublished databases (Black et al., 1997;Dahlheim, 1997;Ford & Ellis, 1999;Olson & Gerrodette, 2008;Towers et al., 2019;McInnes et al., 2021McInnes et al., , 2023. Of the nine encounters with the 49 previously undocumented killer whales, seven included photographs, and two only provided descriptions. ...
In the northeastern Pacific, sightings of small numbers of killer whales (Orcinus orca) of unknown ecotype have been sporadically reported during open ocean marine mammal surveys, pelagic birding expeditions, and high seas fishing operations (Pitman et al., 2001; Pitman & Dutton, 2004; Forney & Wade, 2006; Dahlheim et al., 2008; McInnes et al., 2021; Olson et al., 2023). However, it is unknown whether these oceanic killer whales belong to a mammal-eating ecotype of killer whale, an offshore fish-eating ecotype, or an offshore generalist type. We attempted to determine the ecotype of 49 unknown individuals observed during nine encounters from 1997 to 2021 in the deep oceanic waters far from the coastlines of California and Oregon (> 65 km) based on their foraging behaviors, prey species consumed, morphologies, and the prevalence of cookiecutter shark (Isistius sp.) bite scars. We hypothesize that these killer whales may represent a distinct oceanic subpopulation of transient killer whales or an undescribed oceanic population that feeds on marine mammals and sea turtles in the open ocean beyond the continental shelf break.
... However, the behavior is rare in NRKWs and ARKWs compared to in SRKWs, given the relatively high observation effort (research and whale watching) within portions of the ranges of the NRKW and ARKW populations (Towers et al., 2019). The reason(s) for the differences in occurrence of the behavior between salmon-eating killer whale communities is unknown. ...
Endangered Southern Resident killer whales (Orcinus orca) are fish-eaters that preferentially prey on adult Chinook salmon (Oncorhynchus tshawytscha). Despite being salmon specialists, individuals from all three killer whale pods (J, K, L) have been observed harassing and killing porpoises (family Phocoenidae) without consuming them. Retrospectively , we identified and analyzed 78 episodes of Southern Resident killer whales harassing porpoises between 1962 and 2020, of which 28 resulted in the porpoise's death ("phocoenacide"). Fifty-six episodes involved harbor porpoise (Phocoena phocoena), 13 involved Dall's porpoise (Phocoenoides dalli), and the porpoise species was unreported for nine episodes. Southern Resident killer whales often targeted young porpoises that were similar in size to adult Chinook salmon. † These authors contributed equally to the manuscript.
... Outbreeding in Bigg's killer whales is also promoted by (or potentially drives) this ecotype's greater fluidity in social group membership relative to Resident killer whales, and consequently, Bigg's killer whales have a higher level of genetic diversity (Barrett-Lennard 2000). Dispersing from the natal group either permanently or temporarily, which is observed in both sexes of Bigg's but is especially prevalent in females (Nielsen et al. 2023), may reduce intragroup sexual competition and increase the probability of finding unrelated mates (Baird and Dill 1996;Baird and Whitehead 2000;Towers et al. 2019). Dispersing male Bigg's that travel alone rather than integrating themselves into other social groups (also known as "roving" males; Baird 1994) may do so to increase their chances of encountering and mating with as many unrelated females as possible; however, only eight instances of this type of permanent dispersal have been documented so far for males with living mothers (Nielsen et al. 2023). ...
We present the current available knowledge about sexual behavior and mating systems in the killer whale, Orcinus orca , focusing primarily on the most well-studied ecotype, the Residents of the eastern North Pacific. Resident killer whales display lifetime natal philopatry of both sexes and thus form stable social groupings organized along maternal lines. Inbreeding is minimized via exogamous mating during multigroup aggregations that are diffusely seasonal. Male reproductive success in Residents is highly skewed, likely as a result of female mate choice or possibly intrasexual contest competition (or both), with only the largest and oldest males siring offspring. Female choice for males with large body and appendage sizes likely explains why killer whales as a species have evolved a high degree of sexual dimorphism. Scarring patterns and dorsal fin injuries indicate that breeding-aged males may occasionally engage in aggressive intrasexual competition to secure mates. Young male Residents appear to practice courtship behaviors by engaging in sociosexual play with other males. Coercive mating or mate-guarding in this species has not been observed and appears to be unlikely. Relative testes size, penis length, and penis tip morphology indicate that some sperm competition presumably exists in killer whales and likely co-evolved with female polyandry. Thus, both pre- and postcopulatory sexual selection may occur simultaneously in killer whales, and this species probably has a polygynandrous mating system in which both males and females can breed with multiple partners. Genetic pedigree studies of killer whale ecotypes besides Residents are needed to provide currently lacking but valuable information about mating patterns in other populations.
... In more recent decades, opportunistic winter sightings and encounters in the area (DFO Cetacean Research Program, unpubl. data), recovered carcasses (e.g., Center for Whale Research, 2016;Fisheries and Oceans Canada, 2019), as well as biologging data (Hanson et al., 2017), have documented contemporary use of the area by SRKW, and BKW have been increasingly present in the Salish Sea (Shields et al., 2018;Towers et al., 2019). However, because the NSoG area is not as densely populated as the southern Strait of Georgia and the rest of the Salish Sea, it does not receive as much dedicated or opportunistic effort, especially in winter. ...
Understanding habitat use patterns of animal populations across space and time is fundamental to identifying ecological requirements, and informing threat mitigation and conservation strategies. Persistent data gaps tend to occur with cryptic species in difficult-to-access environments, where the use of appropriate monitoring tools is indispensable for detection. Three populations of threatened and endangered killer whales occur year-round in waters off British Columbia, Canada; however, their winter habitat use patterns are not well known. Here we quantify wintertime use of the northern Strait of Georgia by these sympatric killer whale populations, revealing the importance of this previously understudied region. Using a network of passive acoustic monitoring devices deployed over three winter periods, we examine site-specific and regional patterns of occurrence of Bigg’s, and Southern and Northern Resident killer whales. All three populations frequented these waters in nearly every month from November to April, and across all study years. Bigg’s killer whales were detected most frequently, followed by Southern Residents, then Northern Residents. Population-specific differences in site use was apparent, with Southern Resident detections occurring more often than expected off the southwest side of Texada Island, while Northern Residents appeared to favor the east side of Texada Island. Remarkably, the patterns of winter use we observe in this region by Resident killer whale populations have seemingly persisted for at least 50 years. Additionally, we evaluate and discuss the effect of using multiple simultaneous recorders to characterize habitat use patterns. Lastly, we present a data-driven approach for estimating acoustic residence time, describe inter-population differences in winter residency in the northern Strait of Georgia, and discuss implications for critical habitat designation. This study fills important knowledge gaps related to killer whale winter occurrence off western Canada, highlighting the significance of the northern Strait of Georgia for these at-risk populations.
How has parasitism changed for Alaskan salmon over the past several decades? Parasitological assessments of salmon are inconsistent across time, and though parasite data are sometimes noted when processing fillets for the market, those data are not retained for more than a few years. The landscape of parasite risk is changing for salmon, and long‐term data are needed to quantify this change. Parasitic nematodes of the family Anisakidae (anisakids) use salmonid fishes as intermediate or paratenic hosts in life cycles that terminate in marine mammal definitive hosts. Alaskan marine mammals have been protected since the 1970s, and as populations recover, the density of definitive hosts in this region has increased. To assess whether the anisakid burden has changed in salmonids over time, we used a novel data source: salmon that were caught, canned, and thermally processed for human consumption in Alaska, USA. We examined canned fillets of chum ( Oncorhynchus keta , n = 42), coho ( Oncorhynchus kisutch , n = 22), pink ( Oncorhynchus gorbuscha , n = 62), and sockeye salmon ( Oncorhynchus nerka , n = 52) processed between 1979 and 2019. We dissected each fillet and quantified the number of worms per gram of salmon tissue. Anisakid burden increased over time in chum and pink salmon, but there was no change in sockeye or coho salmon. This difference may be due to differences in the prey preferences of each species, or to differences in the parasite species detected across hosts. Canned fish serve as a window into the past, providing information that would otherwise be lost, including information on changes over time in the parasite burden of commercially, culturally, and ecologically important fish species.
Bigg’s (Transient) killer whales (Orcinus orca) display incredible cooperative hunting techniques and a complex social organization. We describe the predation behavior of Bigg’s killer whales in Monterey Bay, California, over a 30-year period. These killer whales are marine mammal foraging specialists, with aspects of their occurrence, habitat use, association patterns, hunting strategies, and communication calls influenced by this ecological specialization. This population encompasses at least 193 individuals and 44 different matrilines. Bigg’s killer whales off Monterey, California predate 12 different marine mammal species. Within this population, there are six key matriarchs that have played a significant role over the past three decades in 85% of gray whale calf (Eschrichtius robustus) predation events—an important prey in spring. Some killer whales gather in large groups during gray whale hunting season, where they jointly participate in attacks and engage in multi-group socializing for several days. When hunting smaller prey such as seals, sea lions, dolphins, and porpoises, they generally travel in separate matrilines composed of a mother and her non-dispersed offspring. Based on extensive observations, we believe that their prey-specific hunting techniques and their communication calls are likely transferred to subsequent generations through social learning, primarily through imitation. This culturally transmitted information results in sustained knowledge and enhancement of hunting techniques in successive generations. Despite apex predator status and lack of natural predators, Bigg’s killer whale populations are vulnerable to the effects of climate change through potential changes in their marine mammal prey abundance and distribution, and the effects of persistent contaminants such as DDTs and PCBs that could negatively affect their reproductive success and immune system. The current chapter is a descriptive summary of the social dynamics and hunting prowess of mammal hunting killer whales in Monterey Bay. Future investigations are necessary to analyze observed patterns on hunting success, group size dynamics, predation risk effects, and social association patterns.
Understanding the evolution of menopause presents a long-standing scientific challenge1,2,3-why should females cease ovulation prior to the end of their natural lifespan? In human societies, intergenerational resource transfers, for example, food sharing and caregiving, are thought to have played a key role in the evolution of menopause, providing a pathway by which postreproductive females can boost the fitness of their kin.4,5,6 To date however, other late-life contributions that postreproductive females may provide their kin have not been well studied. Here, we test the hypothesis that postreproductive female resident killer whales (Orcinus orca) provide social support to their offspring by reducing the socially inflicted injuries they experience. We found that socially inflicted injuries, as quantified by tooth rake marks, are lower for male offspring in the presence of their postreproductive mother. In contrast, we find no evidence that postreproductive mothers reduce rake marking in their daughters. Similarly, we find no evidence that either reproductive mothers or grandmothers (reproductive or postreproductive) reduce socially inflicted injuries in their offspring and grandoffspring, respectively. Moreover, we find that postreproductive females have no effect on reducing the rake marks for whales in their social unit who are not their offspring. Taken together, our results highlight that directing late-life support may be a key pathway by which postreproductive females transfer social benefits to their male offspring.
Acoustic identification of vocalizing individuals opens up new and deeper insights into animal communications, such as individual-/group-specific dialects, turn-taking events, and dialogs. However, establishing an association between an individual animal and its emitted signal is usually non-trivial, especially for animals underwater. Consequently, a collection of marine species-, array-, and position-specific ground truth localization data is extremely challenging, which strongly limits possibilities to evaluate localization methods beforehand or at all. This study presents ORCA-SPY, a fully-automated sound source simulation, classification and localization framework for passive killer whale (Orcinus orca) acoustic monitoring that is embedded into PAMGuard, a widely used bioacoustic software toolkit. ORCA-SPY enables array- and position-specific multichannel audio stream generation to simulate real-world ground truth killer whale localization data and provides a hybrid sound source identification approach integrating ANIMAL-SPOT, a state-of-the-art deep learning-based orca detection network, followed by downstream Time-Difference-Of-Arrival localization. ORCA-SPY was evaluated on simulated multichannel underwater audio streams including various killer whale vocalization events within a large-scale experimental setup benefiting from previous real-world fieldwork experience. Across all 58,320 embedded vocalizing killer whale events, subject to various hydrophone array geometries, call types, distances, and noise conditions responsible for a signal-to-noise ratio varying from -14.2 dB to 3 dB, a detection rate of 94.0 % was achieved with an average localization error of 7.01∘. ORCA-SPY was field-tested on Lake Stechlin in Brandenburg Germany under laboratory conditions with a focus on localization. During the field test, 3889 localization events were observed with an average error of 29.19∘ and a median error of 17.54∘. ORCA-SPY was deployed successfully during the DeepAL fieldwork 2022 expedition (DLFW22) in Northern British Columbia, with a mean average error of 20.01∘ and a median error of 11.01∘ across 503 localization events. ORCA-SPY is an open-source and publicly available software framework, which can be adapted to various recording conditions as well as animal species.
Age-related changes in the patterns of local relatedness (kinship dynamics) can be a significant selective force shaping the evolution of life history and social behaviour. In humans and some species of toothed whales, average female relatedness increases with age, which can select for a prolonged post-reproductive lifespan in older females due to both costs of reproductive conflict and benefits of late-life helping of kin. Killer whales (Orcinus orca) provide a valuable system for exploring social dynamics related to such costs and benefits in a mammal with an extended post-reproductive female lifespan. We use more than 40 years of demographic and association data on the mammal-eating Bigg's killer whale to quantify how mother-offspring social relationships change with offspring age and identify opportunities for late-life helping and the potential for an intergenerational reproductive conflict. Our results suggest a high degree of male philopatry and female-biased budding dispersal in Bigg's killer whales, with some variability in the dispersal rate for both sexes. These patterns of dispersal provide opportunities for late-life helping particularly between mothers and their adult sons, while partly mitigating the costs of mother-daughter reproductive conflict. Our results provide an important step towards understanding why and how menopause has evolved in Bigg's killer whales.
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