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Live Strandings of Bigg's Killer Whales (Orcinus orca) Along the West Coast of North America
Abstract
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.
... In a review of stranded killer whales in North America, killer whales were found to strand in pursuit of prey; this behavior was otherwise considered rare. These events did not involve a specific sex or age class [13]. Historical records show that many live stranded killer whales have been euthanized or captured for aquariums, where they subsequently died. ...
... Historical records show that many live stranded killer whales have been euthanized or captured for aquariums, where they subsequently died. This review presented five live stranding events since 2002, where all the individuals survived, although one adult male was never seen again [13]. Three adults were stranded on sandy shores and two juveniles were stranded on rocky outcroppings while hunting harbor seals. ...
... Moreover, one adult female was pregnant when stranded and gave birth to a healthy calf several months later. The review concluded that the outcomes from these five strandings indicate that human responses are not always necessary, but when they are, they can help preserve the animals' lives and family bonds [13]. ...
The rescue attempts of stranded whales and euthanasia considerations must include condition assessments of the individual involved, but this is challenged by our insufficient knowledge about the health statuses of these whales. Here, we describe three separate strandings of a young male killer whale (Orcinus orca) in shallow Danish waters during 2021–2022. During the first two stranding events, the whale exhibited remarkable behavior and, after refloating attempts and several kilometers of swimming, it returned to shallow water. This suggests that it actively chose to be in this shallow water, perhaps to ensure free airways and respiration. During the last stranding, it stayed in shallow water for 30 days, during which, euthanasia was considered due to its seemingly worsened condition, including a collapsed dorsal fin. However, suddenly, the whale swam away and, a year later, he was seen alive, confirming that euthanasia would have been the wrong decision. This case raises an important question as to when and under what circumstances active human interventions, such as refloating attempts, should be launched and when euthanasia should be carried out. Every stranding is unique and decisions should be based on thorough considerations of the animal’s health and the chance of a successful rescue.
... In NZ, where there are high rates of orca strandings (Visser, 2013), most events involve single stranded animals who are in good health, but who strand as a result of their method of foraging in shallow waters for rays (Visser, 1999b). Towers et al., (2020a) also believed that the strandings of another orca ecotype (Bigg's) were "accidental out-comes resulting from the intent to capture prey" and in those cases the prey were marine mammals. ...
... Towers et al., (2020a) describe a resighting of two orca (an adult female and her adult male offspring) who stranded in 2011 and were resighted 119 times afterwards (prior to the end of 2019), but there was no intervention applied (other than a single bucket of water). ...
... In NZ, where there are high rates of orca strandings (Visser, 2013), most events involve single stranded animals who are in good health, but who strand as a result of their method of foraging in shallow waters for rays (Visser, 1999b). Towers et al., (2020a) also believed that the strandings of another orca ecotype (Bigg's) were "accidental out-comes resulting from the intent to capture prey" and in those cases the prey were marine mammals. ...
... Towers et al., (2020a) describe a resighting of two orca (an adult female and her adult male offspring) who stranded in 2011 and were resighted 119 times afterwards (prior to the end of 2019), but there was no intervention applied (other than a single bucket of water). ...
... In NZ, where there are high rates of orca strandings (Visser, 2013), most events involve single stranded animals who are in good health, but who strand as a result of their method of foraging in shallow waters for rays (Visser, 1999b). Towers et al., (2020a) also believed that the strandings of another orca ecotype (Bigg's) were "accidental out-comes resulting from the intent to capture prey" and in those cases the prey were marine mammals. ...
... Towers et al., (2020a) describe a resighting of two orca (an adult female and her adult male offspring) who stranded in 2011 and were resighted 119 times afterwards (prior to the end of 2019), but there was no intervention applied (other than a single bucket of water).Shelden et al. (2003) describe an adult male orca who survived a stranding in 1991 and was resighted in 1993, but they do not discuss any assistance that was given to the orca.In comparison, there are a number of orca in NZ who have stranded and received no intervention -and who have also since been resighted, for example NZ21 (aka 'Roundtop'), who has stranded twice whilst foraging for rays and been documented with NZ101 on a number of occasions. He first stranded on the 27 July 2006 and then restranded again on 09 April 2010, with his most recent resighting on 09 June 2020, i.e., the total duration between his first stranding and his most recent sighting was 5,066 days (13 years, 10 months, 13 days) and there were 3,714 days (10 years, 2 months) between his second stranding and his most recent sighting.Likewise, there are other NZ Coastal orca who have survived boat strikes, without intervention. ...
... In NZ, where there are high rates of orca strandings (Visser, 2013), most events involve single stranded animals who are in good health, but who strand as a result of their method of foraging in shallow waters for rays (Visser, 1999b). Towers et al., (2020a) also believed that the strandings of another orca ecotype (Bigg's) were "accidental out-comes resulting from the intent to capture prey" and in those cases the prey were marine mammals. ...
... Towers et al., (2020a) describe a resighting of two orca (an adult female and her adult male offspring) who stranded in 2011 and were resighted 119 times afterwards (prior to the end of 2019), but there was no intervention applied (other than a single bucket of water). ...
Cetaceans harbor a rich and high-specific parasite fauna that can influence hosts’ population dynamics and be used to unveil aspects on their biology. Furthermore, these biotic associations are interesting models to investigate coevolutionary processes in the marine environment. In this chapter, we select a digenean exclusive to cetaceans, Pholeter gastrophilus, as a case study to illustrate the potential of parasitological studies to understand historical and present-day host-parasite interactions in this group of marine mammals. First, we present a brief account of the helminth diversity in cetaceans, as well as the systematics and host records for P. gastrophilus. Second, we discuss evidence on the origin of the association and phylogeography of this species with cetaceans, emphasizing the gaps in basic aspects such as the life cycle and the population structure, especially of Pacific and Black Sea populations. Third, we sum up information on microhabitat selection and life-history strategy, also identifying the relevant spatial scales and host sampling scheme necessaries for future research. Finally, we examine the pathogenic effects of P. gastrophilus and its potential impact at individual and population level. Our bottom-line message is that a comprehensive analysis of parasites of marine mammals also sheds light on host and ecosystem features.
... Prior to 1994, there was an anecdotal report of killer whales intentionally stranding on one of this island's beaches while pursuing harbour seals (Baird & Dill, 1995). The only other documented live-stranding events by Bigg's killer whales in the Salish Sea have been reported as accidental events that most likely occurred while the whales were foraging in shallow water (Towers et al., 2020). Herein, we report the first photo-documented record of Bigg's killer whales intentionally stranding themselves in pursuit of harbour seals in the Salish Sea at a haulout site on Protection Island. ...
... The two killer whale groups were identified by photographs as the T037A and T065A matrilines (known as the T037As and T065As, respectively) (Transient Killer Whale Research Project, unpub. catalog, 2011-2020Towers et al., 2019). When the feeding event concluded, the T037A group departed, while the T065As remained in the area until 1630 h. ...
J. D. McInnes, J. N. Buckmaster, K. D. Cullen, C. R. Mathieson, and J. P. Tawse: Intentional Stranding by Mammal-Hunting Killer Whales (Orcinus orca) in the Salish Sea.
We describe the first documented event of intentional stranding by Bigg's (transient) killer whales in the Salish Sea. This high risk behaviour involves killer whale deliberately stranding in order to capture seals or sea lions hauled out on shore. This behaviour has only been documented in killer whale populations in the Southern Hemisphere.
The event took place at Protection Island, Washington, and involved a commonly encountered killer whale matriline known as the T065As.
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.
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.
Cetacean strandings elicit much community and scientific interest, but few quantitative analyses have successfully identified environmental correlates to these phenomena. Data spanning 1920-2002, involving a total of 639 stranding events and 39 taxa groups from southeast Australia, were found to demonstrate a clear 11-13- year periodicity in the number of events through time. These data positively correlated with the regional persistence of both zonal (westerly) and meridional (southerly) winds, reflecting general long-term and large-scale shifts in sea-level pressure gradients. Periods of persistent zonal and meridional winds result in colder and presumably nutrient-rich waters being driven closer to southern Australia, resulting in increased biological activity in the water column during the spring months. These observations suggest that large-scale climatic events provide a powerful distal influence on the propensity for whales to strand in this region. These patterns provide a powerful quantitative framework for testing hypotheses regarding environmental links to strandings and provide managers with a potential predictive tool to prepare for years of peak stranding activity.
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