Sightings of southern resident killer whales in the Salish Sea 1976-2014: the importance of a long-term opportunistic dataset

Abstract For animals that tend to remain with their natal group rather than individually disperse, group sizes may become too large to benefit individual fitness. In such cases, group splitting (or fission) allows philopatric animals to form more optimal group sizes without sacrificing all familiar social relationships. Although permanent group splitting is observed in many mammals, it occurs relatively infrequently. Here, we use combined generalized modeling and machine learning approaches to provide a comprehensive examination of group splitting in a population of killer whales (Orcinus orca) that occurred over three decades. Fission occurred both along and across maternal lines, where animals dispersed in parallel with their closest maternal kin. Group splitting was more common: (1) in larger natal groups, (2) when the common maternal ancestor was no longer alive, and (3) among groups with greater substructuring. The death of a matriarch did not appear to immediately trigger splitting. Our data suggest intragroup competition for food, leadership experience and kinship are important factors that influence group splitting in this population. Our approach provides a foundation for future studies to examine the dynamics and consequences of matrilineal fission in killer whales and other taxa. Significance statement Group living among mammals often involves long-term social affiliation, strengthened by kinship and cooperative behaviours. As such, changes in group membership may have significant consequences for individuals’ fitness and a population’s genetic structure. Permanent group splitting is a complex and relatively rare phenomenon that has yet to be examined in detail in killer whales. In the context of a growing population, in which offspring of both sexes remain with their mothers for life, we provide the first in-depth examination of group splitting in killer whales, where splitting occurs both along and across maternal lines. We also undertake the first comprehensive assessment of how killer whale intragroup cohesion is influenced by both external and internal factors, including group structure, population and group demography, and resource abundance.

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Satellite Tagging and Biopsy Sampling of Killer Whales at Subantarctic Marion Island: Effectiveness, Immediate Reactions and Long-Term Responses

PLoS ONE ◽

10.1371/journal.pone.0111835 ◽

2014 ◽

Vol 9 (11) ◽

pp. e111835 ◽

Cited By ~ 12

Author(s):

Ryan R. Reisinger ◽

W. Chris Oosthuizen ◽

Guillaume Péron ◽

Dawn Cory Toussaint ◽

Russel D. Andrews ◽

...

Keyword(s):

Marion Island ◽

Killer Whales ◽

Satellite Tagging ◽

Immediate Reactions

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Soundscapes experienced by southern resident killer whales (Orcinus orca) in the Salish Sea and implications of vessel noise

The Journal of the Acoustical Society of America ◽

10.1121/10.0008187 ◽

2021 ◽

Vol 150 (4) ◽

pp. A251-A251

Author(s):

Rianna Burnham ◽

Svein Vagle ◽

Pramod Thupaki ◽

Caitlin O'Neill

Keyword(s):

Orcinus Orca ◽

Killer Whales ◽

Salish Sea ◽

Vessel Noise

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Prey switching by killer whales in the north-east Atlantic: observational evidence and experimental insights

Journal of the Marine Biological Association of the United Kingdom ◽

10.1017/s0025315413001707 ◽

2013 ◽

Vol 94 (6) ◽

pp. 1357-1365 ◽

Cited By ~ 18

Author(s):

Dag Vongraven ◽

Anna Bisther

Keyword(s):

Killer Whale ◽

Large Population ◽

Tooth Wear ◽

Killer Whales ◽

Prey Switching ◽

Photo Identification ◽

North East ◽

The North ◽

Spawning Stock

Studies in the Pacific have identified distinct killer whale ecotypes that are either specialized mammal- or fish-eaters. The different types have developed hunting strategies that would suggest specialization could be more advantageous than generalism. However, it has been suggested, based on long-term dietary markers of tooth wear and stable isotope values, that lineages in the North Atlantic are generalist, but with individual variation in the proportion of prey types consumed. Here, we present the results of ten years of observational and photo-identification data of a population of killer whales that follows the Norwegian spring-spawning stock of Atlantic herring. Although the whales were predominantly observed while feeding upon herring, one pod of herring-eating whales was also observed interacting with seals. This supports the hypothesis based on the long-term markers, of a degree of specialization, with a small number of groups persistently feeding upon mammals, but switching between herring and seals. We further investigated this prey switching by conducting playbacks of herring-eating killer whale sounds to harbour seals at haul-out sites on the herring spawning grounds. We recorded changes in behaviour consistent with an anti-predator response, suggesting the seals perceived the herring-eating killer whales as a potential predatory threat and had not habituated to their calls. This could be due to the risk of herring-eating killer whales switching to mammalian prey, or the difficulty of discriminating between killer whale pods due to the large population size and number of killer whale call dialects in this population, or a combination of both.

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Intentional Stranding by Mammal-Hunting Killer Whales (Orcinus orca) in the Salish Sea

Aquatic Mammals ◽

10.1578/am.46.6.2020.556 ◽

2020 ◽

Vol 46 (6) ◽

pp. 556-560

Author(s):

Josh D. McInnes ◽

Justine N. Buckmaster ◽

Kelsey D. Cullen ◽

Chelsea R. Mathieson ◽

Josh P. Tawse

Keyword(s):

Orcinus Orca ◽

Killer Whales ◽

Salish Sea

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False killer whales (Pseudorca crassidens) around the main Hawaiian Islands: Long-term site fidelity, inter-island movements, and association patterns

Marine Mammal Science ◽

10.1111/j.1748-7692.2008.00200.x ◽

2008 ◽

Vol 24 (3) ◽

pp. 591-612 ◽

Cited By ~ 69

Author(s):

Robin W. Baird ◽

Antoinette M. Gorgone ◽

Daniel J. McSweeney ◽

Daniel L. Webster ◽

Dan R. Salden ◽

...

Keyword(s):

Site Fidelity ◽

Hawaiian Islands ◽

Killer Whales ◽

Association Patterns ◽

Pseudorca Crassidens

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Predicting global killer whale population collapse from PCB pollution

Science ◽

10.1126/science.aat1953 ◽

2018 ◽

Vol 361 (6409) ◽

pp. 1373-1376 ◽

Cited By ~ 73

Author(s):

Jean-Pierre Desforges ◽

Ailsa Hall ◽

Bernie McConnell ◽

Aqqalu Rosing-Asvid ◽

Jonathan L. Barber ◽

...

Keyword(s):

Polychlorinated Biphenyl ◽

Killer Whale ◽

Trophic Levels ◽

Orcinus Orca ◽

Killer Whales ◽

Model Framework ◽

Population Collapse ◽

Mediated Effects ◽

Chemical Class

Killer whales (Orcinus orca) are among the most highly polychlorinated biphenyl (PCB)–contaminated mammals in the world, raising concern about the health consequences of current PCB exposures. Using an individual-based model framework and globally available data on PCB concentrations in killer whale tissues, we show that PCB-mediated effects on reproduction and immune function threaten the long-term viability of >50% of the world’s killer whale populations. PCB-mediated effects over the coming 100 years predicted that killer whale populations near industrialized regions, and those feeding at high trophic levels regardless of location, are at high risk of population collapse. Despite a near-global ban of PCBs more than 30 years ago, the world’s killer whales illustrate the troubling persistence of this chemical class.

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Culture in whales and dolphins

Behavioral and Brain Sciences ◽

10.1017/s0140525x0100396x ◽

2001 ◽

Vol 24 (2) ◽

pp. 309-324 ◽

Cited By ~ 428

Author(s):

Luke Rendell ◽

Hal Whitehead

Keyword(s):

Cultural Transmission ◽

Field Studies ◽

Good Evidence ◽

Killer Whales ◽

Cetacean Species ◽

Learning Abilities ◽

Transmission Mechanisms ◽

Ethnographic Approach ◽

Animal Culture

Studies of animal culture have not normally included a consideration of cetaceans. However, with several long-term field studies now maturing, this situation should change. Animal culture is generally studied by either investigating transmission mechanisms experimentally, or observing patterns of behavioural variation in wild populations that cannot be explained by either genetic or environmental factors. Taking this second, ethnographic, approach, there is good evidence for cultural transmission in several cetacean species. However, only the bottlenose dolphin (Tursiops) has been shown experimentally to possess sophisticated social learning abilities, including vocal and motor imitation; other species have not been studied. There is observational evidence for imitation and teaching in killer whales. For cetaceans and other large, wide-ranging animals, excessive reliance on experimental data for evidence of culture is not productive; we favour the ethnographic approach. The complex and stable vocal and behavioural cultures of sympatric groups of killer whales (Orcinus orca) appear to have no parallel outside humans, and represent an independent evolution of cultural faculties. The wide movements of cetaceans, the greater variability of the marine environment over large temporal scales relative to that on land, and the stable matrilineal social groups of some species are potentially important factors in the evolution of cetacean culture. There have been suggestions of gene-culture coevolution in cetaceans, and culture may be implicated in some unusual behavioural and life-history traits of whales and dolphins. We hope to stimulate discussion and research on culture in these animals.

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Movements and site fidelity of killer whales (Orcinus orca) relative to seasonal and long-term shifts in herring (Clupea harengus) distribution

Marine Biology ◽

10.1007/s00227-017-3187-9 ◽

2017 ◽

Vol 164 (8) ◽

Cited By ~ 10

Author(s):

Filipa I. P. Samarra ◽

S. B. Tavares ◽

J. Béesau ◽

V. B. Deecke ◽

A. Fennell ◽

...

Keyword(s):

Site Fidelity ◽

Clupea Harengus ◽

Orcinus Orca ◽

Killer Whales

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Return of the Salish Sea Harbor Porpoise, Phocoena phocoena: Knowledge Gaps, Current Research, and What We Need to Do to Protect Their Future

Frontiers in Marine Science ◽

10.3389/fmars.2021.618177 ◽

2021 ◽

Vol 8 ◽

Author(s):

Cindy R. Elliser ◽

Anna Hall

Keyword(s):

United States ◽

The United States ◽

Phocoena Phocoena ◽

Ecological Data ◽

Salish Sea ◽

Harbor Porpoise ◽

Knowledge Gaps ◽

Holistic View ◽

Photo Identification

The harbor porpoise (Phocoena phocoena) is one of the most abundant coastal cetacean species in the Northern Hemisphere with differential levels of regional knowledge. Gaps are particularly evident for the Pacific subspecies Phocoena phocoena vomerina. In the Salish Sea (a transboundary body of water spanning between Washington, United States and British Columbia (BC), Canada), there is a dearth of information on many aspects of the biology, ecology, behavior, sociality, and regionally specific threats. Here we present a case study of the Salish Sea harbor porpoise, combining historical and current research, from both BC and Washington, to provide a more holistic view of this species’ status, the knowledge continuum and gaps, risks from identified threats and what current research and collaborations are revealing about this enigmatic species. The Salish Sea harbor porpoise was abundant to the 1940s and 1950s, but by the 1990s their numbers were greatly reduced, and all but absent in some areas. By the early 2000s, numbers had resurged, and harbor porpoise are now once again found throughout much of the Salish Sea. Despite this, studies focused on Salish Sea harbor porpoises have been limited until recently. Current long-term research has been conducted from vessels and land in both Canada and the United States. Multi-faceted work using techniques including photo-identification (photo-ID), behavioral visual observations, acoustics, commercial fishery surveys, sighting reports, citizen science and other ecological data have provided insight into the seasonal variation in density and abundance, site fidelity, reproduction, by-catch rates, foraging and the identification of important habitats that are used intra- and inter-annually in this region. These may represent culturally and biologically significant habitats for Salish Sea harbor porpoise. Collaborations within and outside of the Salish Sea have revealed consistencies and dissimilarities between different communities or populations; indicating that some aspects are more uniform for the species, while others may be community or population specific. The importance of long-term broad and fine-scale research is highlighted, as well as recommendations to further close the knowledge gaps and reduce the known human threats within the Salish Sea.

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