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Photo-identification Catalogue of Bigg’s (Transient) Killer Whales From Coastal Waters of British Columbia, Northern Washington, and Southeastern Alaska.
Abstract
Killer whales are easily recognizable by the appearance of their naturally occurring
markings in both photographs and during field observations. This report presents updated
identification images and demographic data for Bigg's (transient) killer whales known from
numerous encounters between 1974 and 2012 in the coastal waters of British Columbia, northern
Washington, and southeastern Alaska. These data are intended to facilitate studies and
observations of Bigg's killer whales and serve as a supplement to future publications.
... For example, although killer whales (Orcinus orca) are one of the most studied and widespread species of cetacean, only a few observations of aggression between individuals of the same population have been reported (see 27 ). Nevertheless, individuals of all sex and age classes from many killer whale populations around the world have scars on their bodies from the teeth of conspecifics [28][29][30][31][32][33] . These scars may originate from rough interactions between or within sex and age classes but, causes of their occurrence likely vary in nature and among populations. ...
... This benefits inclusive fitness of the female because a positive relationship exists between reproductive success and age in male killer whales 45,46 . This combined with a prediction by Connor et al. 47 that post-reproductive female killer whales may play a role in acquiring mates for their adult male offspring suggests that T068's active involvement in this event was sexually selected, especially considering that T068A is of a reproductively mature age 30,46 . The sexual selection hypothesis requires that the infanticidal male does not kill his own offspring, that the event provides a near future mating opportunity with the infants' mother and that he sires offspring with her 12 . ...
... Digital audio, video and images were obtained in the field while observations were taking place from a 5 metre motor vessel. The individual killer whales and their genealogies were identified using Towers et al. 30 . Data on age, sex, associations and observations from other encounters were obtained from the database on this population maintained for the Pacific Biological Station (Fisheries and Oceans Canada). ...
Infanticide can be an extreme result of sexual conflict that drives selection in species in which it occurs. It is a rarely observed behaviour but some evidence for its occurrence in cetaceans exists in three species of dolphin. Here we describe observations of an adult male killer whale (Orcinus orca) and his postreproductive mother killing a neonate belonging to an unrelated female from the same population in the North Pacific. This is the first account of infanticide reported in killer whales and the only case committed jointly by an adult male and his mother outside of humans. Consistent with findings in other social mammals, we suggest that infanticide is a sexually selected behaviour in killer whales that could provide subsequent mating opportunities for the infanticidal male and thereby provide inclusive fitness benefits for his mother.
... To our knowledge, apart from O. orca, for which several records exist (e.g. Visser, 1998;Bigg et al. 1987;Baird & Stacey, 1989;Matkin et al. 2008;Towers et al. 2012Towers et al. , 2015, bending dorsal fins in freeranging cetaceans have been only documented anecdotally in four other species: the common bottlenose dolphin Tursiops truncatus (Wilson et al. 1997;Baird & Gorgone, 2005), the false killer whale Pseudorca crassidens (Baird & Gorgone, 2005), the white-beaked dolphin Lagenorhynchus albirostris (Higdon & Snow, 2008), and the dusky dolphin Lagenorhynchus obscurus (K€ ugler & Orbach, 2014). ...
... Previously, bent dorsal fins on cetaceans have only been reported for single species or in one specific area (Visser, 1998;Baird & Gorgone, 2005;Higdon & Snow, 2008), many of which lack detailed information and have not focused specifically on such abnormalities (e.g. Ford et al. 1994;Baird & Stacey, 1989;Wilson et al. 1997;Olson & Gerrodette, 2008;K€ ugler & Orbach, 2014;Towers et al. 2012Towers et al. , 2015Bertulli et al. 2016). The present review adds 12 species to the list of free-ranging cetaceans displaying bent dorsal fins. ...
... data). Although this comparison between populations is not comprehensive, these findings, along with those in Bigg (1982), Bigg et al. (1987), Baird & Stacey (1989), Ford et al. (1994Ford et al. ( , 2000, Black et al. (1997), Visser (1998), Ford & Ellis (1999), Matkin et al. (1999), Ellis et al. (2007Ellis et al. ( , 2008Ellis et al. ( , 2011, Olson & Gerrodette (2008), Towers et al. (2012Towers et al. ( , 2015, Guerrero-Ruiz et al. (2005) and this study Baird & Gorgone (2005), support the idea that bent dorsal fins are rare in nature. ...
Laterally bent dorsal fins are rarely observed in free-ranging populations of cetaceans, contrary to captivity, where most killer whale Orcinus orca adult males have laterally collapsed fins. This topic has been poorly explored, and data/information on its occurrence and possible causes are limited. The present study: (i) undertakes a review of the available information on bent dorsal fins in free-ranging cetaceans, and updates it with new records, (ii) reports on the proportion of bent fins in different study populations, and (iii) discusses possible causes. An empirical approach based on bibliographic research and compilation of 52 new records collected worldwide resulted in a total of 17 species of cetaceans displaying bent dorsal fins. The species with the highest number of records (64%) and from most locations was O. orca. On average, individuals with bent dorsal fins represent < 1% of their populations, with the exception of false killer whales Pseudorca crassidens and O. orca. While line injuries associated with fisheries interactions may be the main cause for P. crassidens, and the vulnerability to health issues caused by the evolutionary enlargement of the fin may be the cause for O. orca adult males, factors contributing to this abnormality for other species are still unclear. The occurrence of bent dorsals could be influenced by a set of variables rather than by a single factor but, irrespective of the cause, it is suggested that it does not directly affect the animals' survivorship. While still rare in nature, this incident is more common (at least 101 known cases) and widespread (geographically and in species diversity) than hypothesized, and is not confined only to animals in captive environments. Investigation into the occurrence of bent fins may be an interesting avenue of research.
... We hypothesized that there is a change in mammal-eating killer whale occurrence and group size over the 1987–2010 time period. The potential change could be due to an increase in prey abundance and occurrence in the Salish Sea from 1987–2010, or an overall increase in the size of the mammal-eating killer whale population (Ford et al. 2007, Towers et al. 2012). However, a causal relationship between increased prey and changes in killer whale occurrence and behavior cannot be identified from the sighting data. ...
... existing long-term catalogs, individual killer whales were identified by unique markings (Bigg et al. 1987, Ford and Ellis 1999, Towers et al. 2012). Mammal-eating killer whales travel in matrilineal groups with dispersal occurring for some adult males and for females that have offspring of their own (Bigg et al. 1987, Ford and Ellis 1999, Baird and Whitehead 2000). ...
... The Wilcoxon rank-sum test was used to compare mean and modal group sizes between the two time periods. Matrilineal groups were classified based on identifications (Towers et al. 2012) in order to examine differences in the groups of whales most commonly occurring in the Salish Sea. There were 28 matrilines identified and defined for this study that were documented more than once in the Salish Sea in the two periods (Appendix 1). ...
The primary prey species of mammal-eating killer whales in the Salish Sea, the inland waters of southern British Columbia and Washington state, have experienced dramatic increases in population abundances in the last 25 years. It is possible that changes in prey abundance over time have resulted in changes in predator spatial use, occurrence and group size. Focused studies of mammal-eating killer whale behavior in the area were undertaken from 1987-1993, and an extensive record of sightings with confirmed identifications was available from 2004-2010. Changes in occurrence across years, months, and subareas of the Salish Sea were examined as well as changes in group size and in the identity of specific matrilines using the area. Occurrence of mammal-eating whales increased significantly from 2004-2010 with different seasonal peaks compared to 1987-1993. Different matrilines occurred in different seasons, time periods, and subareas. Group size was larger in 2004-2010 than in 1987-1993. The whales may be increasing use of the area due to increasing prey abundance or an overall increase in the whale population size. Changes in seasonal patterns of occurrence and the increase in group size between the two periods could be due to increased prey diversity.
... Among spread within this region (O'Connor et al., 2009; these cases, four involved Bigg's killer whales Towers, 2017). from the GOA population and occurred in Cook A total of five animals were involved in the Inlet, Alaska, between 1991and 2002(Shelden LSEs reported herein, and each individual had et al., 2003, whereas the four cases reported herein been photo-identified prior to the LSE (Black only involved individuals from the WCT popula-et al., 1997;Towers et al., 2012). All individution and occurred between northern Washington als survived the LSEs, but subsequent detection and southeastern Alaska from 2002 to 2015. ...
Killer whales are known to live strand in many regions around the world. Some populations regularly and repeatedly do so in pursuit of prey, but this behaviour is otherwise relatively rare. Off the west coast of North America, historical records of live stranded killer whales indicate that most individuals perished, were euthanized, or captured for aquariums where they subsequently died. Few details are available on which of the three culturally distinct killer whale ecotypes in this region have been involved in live stranding events (LSEs) and on the survival of any individuals that were able to unstrand. In this article, we report details on four LSEs since 2002 and, together with previous records, show that all live-stranded killer whales documented in this region during the last four decades have been of the Bigg’s ecotype. There was no predominant sex or age class involved in these events, but among the five individuals reported herein, all three adults stranded on sandy shores, whereas both juveniles stranded on rocky outcroppings while hunting harbour seals. Stranded individuals were kept cool and wet by human responders during three of the four LSEs, and efforts were twice made to move the animals off the shore. All individuals survived the LSEs, although one adult male was never seen again. The other four individuals rejoined their respective families soon after becoming unstranded and have been photo-identified with them on numerous occasions since. One adult female that was pregnant when stranded gave birth to a healthy calf several months later. These results indicate that (1) human responses to live-stranded killer whales are not always necessary, but when they are, they can help preserve their lives, family bonds, and culture and (2) LSEs are a natural risk associated with the foraging ecology of the Bigg’s killer whale ecotype.
... These photographs were taken both opportunistically and as part of dedicated photo-identification studies over a 20 yr period. Prior to our study, all photographs had been matched to catalogs of previously photo-identified individuals of known ecotype (Dahlheim et al. 1997;Ford et al. 2000;Ellis et al. 2011;Towers et al. 2012Towers et al. , 2015. In the case of western Alaska, where whales are encountered less EMMONS ET AL.: VARIATION IN KILLER WHALE MORPHOLOGY frequently, individuals were included only if their ecotype had been confirmed by genetic analysis or association with individuals of known ecotype (Zerbini et al. 2007). ...
In the northeastern Pacific Ocean, there are three “ecotypes” of killer whales that differ in diet, ecology, behavior, acoustics, genetics, and morphology. Previous attempts to describe the morphological differences among populations of killer whales (Orcinus orca) have been limited to descriptive accounts or categorical studies. We used elliptical Fourier analysis (EFA) to quantify shape differences of dorsal fins and pigmentation patterns among the ecotypes from photo‐identification data of more than 500 individuals. Variation in shapes of the dorsal fin, saddle patch, and eye patch were successfully quantified using EFA, and there were highly significant (P < 0.01) differences among the ecotypes in all three morphological traits. The ability of EFA to discriminate ecotypes based on dorsal fin and eye patch shapes was substantial, while it did not perform as well for saddle patches. Visualization of the shape variation along principal component axes mirrored previous descriptions of the differences among ecotypes. Although the degree of inheritance of morphology in killer whales has not been determined, these results are consistent with previous inference of reduced gene flow between the ecotypes, and introduces elliptical Fourier analysis to the study of cetacean morphometrics.
... Their primary prey, harbor seals, also experienced rapid growth during this time (DFO 2009). Since 2008, transient killer whale mortality has been low and recruitment has been high (Towers et al. 2012). Transient killer whales have substantially higher contaminant burdens , but they do not appear to be experiencing nutritional stress or adverse health effects. ...
... Killer whales in Canadian Pacific coastal waters have been studied by means of photographic identification of individuals from natural markings for four decades. Field studies using this technique have been undertaken each year since the early 1970s (Bigg et al. 1987(Bigg et al. , 1990Ford and Ellis 1999;Ford et al. 2007;Towers et al. 2012). This long-term effort has resulted in an archive of identification photographs collected from 10,580 encounters 1 (up to 2012) Black et al. (1997) and Dahlheim et al. (2008), and these are included in this analysis. ...
The social lives of animals are defined by group dynamics based on the nature and strength of associations and movements between individuals, often resulting in highly complex and interconnected social networks. However, understanding of how environmental variables may shape this structure is poorly understood. Within the inland waters of Washington State and southern Vancouver Island, British Columbia, mammal- eating Bigg’s (transient) killer whales occur in relatively small, but stable social groups. Group size and occurrence in recent years has increased, coinciding with a growing whale watching industry. Given the central importance of the social network within killer whale population dynamics, such as the maintenance of cooperation and cultural transmission of information, shifts in social network structure caused by environmental processes may have significant ecological and evolutionary consequences. Thus, it is reasonable to assume that the increased presence of Bigg’s killer whales within the Salish Sea leaves them susceptible to the various and growing anthropogenic pressures within this area. Utilizing a long-term data set (1987-2015), the objectives of this doctoral study are to: (1) identify the level(s) of preferred associations and social differentiation within Bigg’s societies relative to foraging specializations; (2) re-evaluate and compare historical measures and persistence of Bigg’s sociality, including demographic influences
ii
and dispersion patterns; and, (3) assess the extent to which individual sociality can predict received vessel traffic levels, as well as other variables driving targeted whale watching. The results of this work will better clarify the social dynamics and population structure of Bigg’s killer whales and will thus inform on proper management of this conservation unit. Likewise, the combined evaluation of social dynamics and anthropogenic pressures (vessel traffic) experienced by this population can provide key information that may enable managers to implement proper measures to mitigate anthropogenic impacts. Finally, the results of this analysis will serve as a platform for further evaluating the predator-prey dynamics of Bigg’s killer whale stocks that are central to the Salish Sea ecosystem.
The inland waters of Washington State and southern British Columbia, collectively known as the Salish Sea, comprise key habitat for two regional populations of killer whales ( Orcinus orca ): the mammal-eating West Coast Transients and the endangered fish-eating Southern Residents. These two populations are genetically distinct and may avoid each other. Transient killer whale usage of the Salish Sea has been previously assessed over two seven-year time periods, showing an increase from 1987 to 2010. We documented a continued significant increase in mammal-eating killer whale presence in the Salish Sea from 2011 to 2017, with intra- and inter-annual variability and with record sightings in 2017. This continued increase, likely in response to abundant marine mammal prey, is related to both a growing population and an increase in the number of West Coast Transients visiting the area. Additionally, a negative binomial regression shows that absence of Southern Residents is correlated to transient presence. Finally, both populations of killer whales have been linked to regional harbor seal populations; harbor seals are salmonid-eating competitors of the Southern Residents and are prey for the mammal-eating transients. With Southern Residents listed as endangered, culling harbor seals has been proposed as a measure to help in their recovery. With this in mind, we developed an energetic model to assess the minimum number of harbor seals consumed by transient killer whales. Using the actual number of whales present in each age-sex class for each day of the year, we estimate that, at a minimum, transients in the Salish Sea consumed 1090 seals in 2017. This is more than 2% of the 2014 estimated harbor seal population the Salish Sea. The population controlling effects of transient killer whale predation on harbor seals should be considered when evaluating any pinniped management actions in the Salish Sea.
Historically, Fin Whales (Balaenoptera
physalus) were relatively common off the west coast
of North America but very few records of their
occurrence in waters between Vancouver Island and
continental North America exist. To confirm their
presence in these waters we collected photographs
documenting at least 13 unique individuals during 43
encounters from 1999 to 2017. These records are the
first of live Fin Whales in Queen Charlotte, Johnstone,
Georgia and Juan De Fuca Straits and are also the only
confirmed sightings between Vancouver Island and
continental North America since 1930. Additionally, 12
dead Fin Whales all with evidence of ship strikes are
reported in these waters between 1986 and 2017. Most
(88%) sightings of live Fin Whales occurred between
July and October and no individuals were documented
dead or alive between January and April. We suggest
that Fin Whales in coastal waterways may be at greater
risk to ship strikes and predation by mammal-eating
Killer Whales (Orcinus orca) than in less confined
waters further offshore.
The social organization of mammal-eating "transient" killer whales (Orcinus orca) was studied off southern Vancouver Island from 1985 through 1996. Strong and long-term associations exist between individual transients, so sets of individuals with consistently high association levels, termed pods, can be delineated. Pods consist of individuals of mixed ages and sexes, and typically contain an adult female and one or two offspring (averaging 2.4 individuals). The mother-offspring bond remains strong into adulthood for some male (and less often for female) offspring. Other males disperse from their maternal pod and appear to become "roving" males, spending some of their time alone, and occasionally associating with groups that contain potentially reproductive females. These males appear to have no strong or long-term relationships with any individuals, and adult male - adult male associations occur significantly less often than expected by chance. Females that disperse from their natal pod appear to be gregarious (having high average association rates) but socially mobile (having low maximum association rates). Differences in social organization from the sympatric fish-eating "resident" killer whales (where no dispersal of either sex occurs) likely relate to differences in foraging ecology. Transient killer whales maximize per capita energy intake by foraging in groups of three individuals, whereas no such relationship has been documented for resident killer whales.
Resident killer whales (Orcinus orca) found in coastal waters of the cold-temperate northeastern Pacific are fish-feeding predators that specialize on Pacific salmon. Field studies have shown that although most available salmonids are consumed, Chinook salmon (Oncorhynchus tshawytscha) is the whales’ primary prey species, most likely because of its large size, high lipid content, and year-round occurrence in coastal waters. Chinook salmon availability appears to be important to the survival and recovery of resident killer whale populations. In this report we describe the results of recent field studies and analyses aimed at improving our understanding of the role played by Chinook salmon in the seasonal foraging ecology and energetics of resident killer whales. An additional 410 prey items identified from scale and tissue samples collected at the sites of resident feeding events provide further support for the importance of Chinook salmon in most seasons and coastal areas. Genetic stock identification of prey samples indicate that killer whales feed on Chinook salmon originating from a variety of regions between Southeast Alaska and Oregon, with stocks in the Fraser River system being of particular importance both coast-wide and in Critical Habitats. An updated analysis confirms the long-term correlation between survival of resident killer whales and range-wide Chinook abundance, though recent declines in Chinook abundance have not yet been associated with increased mortality rates. Estimates of Chinook salmon consumption based on daily prey energy requirements and diet composition suggest that resident killer whale populations at their current abundance may require over 1,000,000 Chinook per year, roughly equivalent to recent annual levels of harvests of this species in commercial and recreational marine fisheries. Estimates of Chinook salmon requirements for northern and southern resident killer whale populations in their Critical Habitats are also provided, as is an estimate of the Chinook abundance that would be required to support killer whale recovery over the next decade. Although the information in this report may be useful for future conservation and management of resident killer whales and their primary prey, further studies are needed to resolve existing uncertainties about year-round diet composition and feeding rates.
Two forms of killer whale (Orcinus orca), resident and transient, occur sympatrically in coastal waters of British Columbia, Washington State, and southeastern Alaska. The two forms do not mix, and differ in seasonal distribution, social structure, and behaviour. These distinctions have been attributed to apparent differences in diet, although no comprehensive comparative analysis of the diets of the two forms had been undertaken. Here we present such an analysis, based on field observations of predation and on the stomach contents of stranded killer whales collected over a 20-year period. In total, 22 species of fish and 1 species of squid were documented in the diet of resident-type killer whales; 12 of these are previously unrecorded as prey of O. orca. Despite the diversity of fish species taken, resident whales have a clear preference for salmon prey. In field observations of feeding, 96% of fish taken were salmonids. Six species of salmonids were identified from prey fragments, with chinook salmon (Oncorhynchus tshawytscha ) being the most common. The stomach contents of stranded residents also indicated a preference for chinook salmon. On rare occasions, resident whales were seen to harass marine mammals, but no kills were confirmed and no mammalian remains were found in the stomachs of stranded residents. Transient killer whales were observed to prey only on pinnipeds, cetaceans, and seabirds. Six mammal species were taken, with over half of observed attacks involving harbour seals (Phoca vitulina). Seabirds do not appear to represent a significant prey resource. This study thus reveals the existence of strikingly divergent prey preferences of resident and transient killer whales, which are reflected in distinctive foraging strategies and related sociobiological traits of these sympatric populations. 1471
A community comprises individuals that share a common range and associate with one another; a pod is a group of individuals within a community that travels together the majority of the time; a subpod is a group of individuals that temporarily fragments from its pod to travel separately; an intra-pod group consists of a cohesive group of individuals within a subpod that always travels in close proximity. Communities contain 3-16 (mean 9.5) pods; pods contain 1-3 (mean 1.7) subpods, subpods contain 1-11 (mean 1.9) intra-pod groups and intra-pod groups contain 2-9 (mean 3.6) individuals. Genealogical trees indicate that intra-pod groups are matrilines. A matrilineal group typically comprises of 2-3 generations (range 1-4; mean 2.3) and a generalized matrilineal group consists of a grandmother, her adult son, her adult daughter and the offspring of her daughter. Matrilineal groups are the basic unit of social organization. -from Authors
The social structure and genealogical relationships of resident killer whale pods in Prince William Sound, Alaska, are inferred from association analysis and direct observation. During 1984-95 a total of 2444 hours of observation were made and 36,009 photographs were taken of identifiable killer whales. Cole's association index and a point correlation coefficient index were used to test the statistical significance and strength of associations between individuals, and a clustering procedure was used to delineate group structure. A total of 202 whales were grouped into 9 pods. Genealogical relationships were inferred from the strength of bonds among pod members. Genealogical trees suggested that intrapod groups were matrilineal in structure. Splitting of one pod (AN pod) was observed during the study; however, there was no splitting of matrilineal groups.
Two sympatric populations of "transient" (mammal-eating) killer whales were photo-identified over 27 years (1984-2010) in Prince William Sound and Kenai Fjords, coastal waters of the northern Gulf of Alaska (GOA). A total of 88 individuals were identified during 203 encounters with "AT1" transients (22 individuals) and 91 encounters with "GOA" transients (66 individuals). The median number of individuals identified annually was similar for both populations (AT1=7; GOA=8), but mark-recapture estimates showed the AT1 whales to have much higher fidelity to the study area, whereas the GOA whales had a higher exchange of individuals. Apparent survival estimates were generally high for both populations, but there was a significant reduction in the survival of AT1 transients after the Exxon Valdez oil spill in 1989, with an abrupt decline in estimated abundance from a high of 22 in 1989 to a low of seven whales at the end of 2010. There was no detectable decline in GOA population abundance or survival over the same period, but abundance ranged from just 6 to 18 whales annually. Resighting data from adjacent coastal waters and movement tracks from satellite tags further indicated that the GOA whales are part of a larger population with a more extensive range, whereas AT1 whales are resident to the study area.