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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.
... Southern residents Fish (mainly salmon) (Ford & Ellis, 2006) 4.33 (1-16) (Center for Whale Research) Natal philopatry of males and females, nonlocal mating (Bigg et al., 1987) (but see Ford et al. (2018)) Northern residents Fish (mainly salmon) (Ford & Ellis, 2006) 6.5 (1-19) (Towers et al., 2020) Natal philopatry of males and some females, nonlocal mating (Barrett-Lennard & Ellis, 2001;Bigg et al., 1987) Bigg's West Coast Transients (WCT) (Sharpe et al., 2019) Marine mammals (mainly pinnipeds and small cetaceans) (Ford & Ellis, 1999) 3.9 (1-8) (Towers et al., 2019) Some dispersal of males and females from natal group, non-local mating inferred (Baird & Whitehead, 2000;Ford & Ellis, 1999) born into a social unit ("matriline") consisting of their mother, siblings, and other more distant relatives . As they age, their own sons replace more distantly related males in the matriline, increasing their average local relatedness to the group over time . ...
... Both populations of residents are specialist fish-eaters with salmon making up almost all of their prey Olesiuk et al., 1990), whereas Bigg's killer whales are specialized in hunting marine mammals (Ford & Ellis, 1999). This differentiation in diet is reflected in the social behavior of the ecotypes with resident killer whales typically being observed traveling in larger social groups consisting of several maternal groups, compared with Bigg's killer whales (Towers et al., 2019(Towers et al., , 2020. The mean group size of cohesive maternal groups however is similar for the two ecotypes (Table 1; Towers et al., 2020). ...
... Sex was determined based on the pigmentation of the ventral side of genital or mammary slits, the presence of neonates, or the size and shape of the dorsal fin of adults (Table 2). We therefore limited our analysis to a subset of the most commonly documented individuals in this population (Towers et al., 2019). We used the photo-identification data from all populations in the format of a capture-mark-recapture sighting matrix, that is, absence/presence for each individual during each year. ...
The extended female post-reproductive lifespan found in humans and some toothed whales remains an evolutionary puzzle. Theory predicts demographic patterns resulting in increased female relatedness with age (kinship dynamics) can select for a prolonged post-reproductive lifespan due to the combined costs of inter-generational reproductive conflict and benefits of late-life helping. Here we test this prediction using >40 years of longitudinal demographic data from the sympatric yet genetically distinct killer whale ecotypes: resident and Bigg’s killer whales. The female relatedness with age is predicted to increase in both ecotypes, but with a less steep increase in Bigg’s due to their different social structure. Here, we show that there is a significant post-reproductive lifespan in both ecotypes with >30% of adult female years being lived as post-reproductive, supporting the general prediction that an increase in local relatedness with age predisposes the evolution of a post-reproductive lifespan. Differences in the magnitude of kinship dynamics however, did not influence the timing or duration of the post-reproductive lifespan with females in both ecotypes terminating reproduction before their mid-40s followed by an expected post-reproductive period of ~20 years. Our results highlight the important role of kinship dynamics in the evolution of a long post-reproductive lifespan in long-lived mammals, while further implying that the timing of menopause may be a robust trait that is persistent despite substantial variation in demographic patterns among population.
... 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.
... Additionally, citizen science allows volunteers to meaningfully contribute to scientific endeavors, aiding in increasing scientific literacy and trust in scientific processes (Tulloch et al., 2013). There have been notable examples of citizen science projects resulting in effective conservation management, including detecting population declines of monarch butterflies (Danaus plexippus; Schultz et al., 2017), implementing policies to protect British breeding birds (Greenwood, 2003), and monitoring killer whale (Orcinus orca) populations (Towers et al., 2019). ...
Successful conservation efforts often require novel tactics to achieve the desired goals of protecting species and habitats. One such tactic is to develop an interdisciplinary, collaborative approach to ensure that conservation initiatives are science-based, scalable, and goal-oriented. This approach may be particularly beneficial to wildlife monitoring, as there is often a mismatch between where monitoring is required and where resources are available. We can bridge that gap by bringing together diverse partners, technologies, and global resources to expand monitoring efforts and use tools where they are needed most. Here, we describe a successful interdisciplinary, collaborative approach to long-term monitoring of beluga whales (Delphinapterus leucas) and their marine ecosystem. Our approach includes extracting images from video data collected through partnerships with other organizations who live-stream educational nature content worldwide. This video has resulted in an average of 96,000 underwater images annually. However, due to the frame extraction process, many images show only water. We have therefore incorporated an automated data filtering step using machine learning models to identify frames that include beluga, which filtered out an annual average of 67.9% of frames labelled as “empty” (no beluga) with a classification accuracy of 97%. The final image datasets were then classified by citizen scientists on the Beluga Bits project on Zooniverse (https://www.zooniverse.org). Since 2016, more than 20,000 registered users have provided nearly 5 million classifications on our Zooniverse workflows. Classified images are then used in various researcher-led projects. The benefits of this approach have been multifold. The combination of machine learning tools followed by citizen science participation has increased our analysis capabilities and the utilization of hundreds of hours of video collected each year. Our successes to date include the photo-documentation of a previously tagged beluga and of the common northern comb jellyfish (Bolinopsis infundibulum), an unreported species in Hudson Bay. Given the success of this program, we recommend other conservation initiatives adopt an interdisciplinary, collaborative approach to increase the success of their monitoring programs.
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\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$-14.2$$\end{document} dB to 3 dB, a detection rate of 94.0 % was achieved with an average localization error of 7.01∘\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$^\circ$$\end{document}. 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∘\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$^\circ$$\end{document} and a median error of 17.54∘\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$^\circ$$\end{document}. ORCA-SPY was deployed successfully during the DeepAL fieldwork 2022 expedition (DLFW22) in Northern British Columbia, with a mean average error of 20.01∘\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$^\circ$$\end{document} and a median error of 11.01∘\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$^\circ$$\end{document} 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.
Aerial photogrammetry has provided increased power for monitoring the health of individuals in the endangered population of Southern Resident killer whales (SRKW, Orcinus orca) in the eastern North Pacific. These data have shown evidence of nutritional stress, with individual growth and body condition correlating with the availability of their primary prey, Chinook salmon (Oncorhynchus tshawytscha). We used drones to derive similar but novel photogrammetry measurements from a sympatric population of mammal‐eating Bigg's killer whales (BKWs) that has been increasing in abundance in recent decades. From 2014 to 2019 we photographed 95 individual BKWs in Canadian waters off Vancouver Island and US waters in the Salish Sea; we estimated asymptotic lengths of 6.4 m for adult females and 7.3 m for adult males, both longer than corresponding length estimates for SRKWs. As a proxy for body condition, we measured head width at a standardized distance behind the blowhole, expressed as proportion of the length between the blowhole and dorsal fin, and estimated that on average, all age/sex classes of BKWs were more robust than corresponding classes of SRKWs. These differences likely reflect divergent adaptive selection in these prey‐specialist ecotypes, but may also partially indicate recent impacts of differential prey availability.
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