Orca (Killer Whale) – Orcinus orca

[sam1]

Apparently the recent attacks might be a retaliation.

www.theguardian.com/environment/2020/oct/06/previous-incident-may-have-led-orcas-to-target-boats-say-experts-spain-portugal

[elosha11]

That's an interesting article. The researchers could have explained themselves a little better however. They say the orcas may be attacking the yachts because of the speed of the boat. I assume they're referring to the relatively slow speed? Unlike a speedboat, these Yachts are far easier for the Orcas to catch up to and ram? That would make sense, but the researchers don't come out and directly say it.

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They're supposedly attacking the boats because they want the boats to slow down.

"“The trigger for this strange and novel behaviour could have been an aversive incident that the orcas had with a boat, and in which the speed of the boat could have been a critical factor,” the working group said in a statement on Tuesday.

“For the moment, we have no clear evidence of when it happened, nor can we say for sure what kind of boat may have been involved, nor whether the incident was accidental or deliberate.”

As a result of the possible incident, said the researchers, the orcas may have felt compelled to act when they saw a sailboat in order to to slow it down by going after its rudder."

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A recently discovered orca ecotype: onlinelibrary.wiley.com/doi/abs/10.1111/mms.12748?af=R

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There are two sympatric ecotypes in northwestern Europe. One (Type 1) is a generalist that preys upon fish and seals, while the other (Type 2) is a specialist of other cetaceans. Type 2 males are also substantially bigger than type 1 males (maximum lengths of 8.5 vs 6.6 meters).

www.orcanetwork.org/nathist/NoAtlantictypes.pdf

Also, just so I don't lose it, a summary of varying diets in different ecotypes in p. 192 of this book.

www.google.com/books/edition/Marine_Mammals_of_the_World/sc-cBAAAQBAJ?hl=en&gbpv=1&dq=type+c+orca+antarctic+toothfish&pg=PA192&printsec=frontcover

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Endangered predators and endangered prey: Seasonal diet of Southern Resident killer whales

Understanding diet is critical for conservation of endangered predators. Southern Resident killer whales (SRKW) (Orcinus orca) are an endangered population occurring primarily along the outer coast and inland waters of Washington and British Columbia. Insufficient prey has been identified as a factor limiting their recovery, so a clear understanding of their seasonal diet is a high conservation priority. Previous studies have shown that their summer diet in inland waters consists primarily of Chinook salmon (Oncorhynchus tshawytscha), despite that species’ rarity compared to some other salmonids. During other times of the year, when occurrence patterns include other portions of their range, their diet remains largely unknown. To address this data gap, we collected feces and prey remains from October to May 2004–2017 in both the Salish Sea and outer coast waters. Using visual and genetic species identification for prey remains and genetic approaches for fecal samples, we characterized the diet of the SRKWs in fall, winter, and spring. Chinook salmon were identified as an important prey item year-round, averaging ~50% of their diet in the fall, increasing to 70–80% in the mid-winter/early spring, and increasing to nearly 100% in the spring. Other salmon species and non-salmonid fishes, also made substantial dietary contributions. The relatively high species diversity in winter suggested a possible lack of Chinook salmon, probably due to seasonally lower densities, based on SRKW’s proclivity to selectively consume this species in other seasons. A wide diversity of Chinook salmon stocks were consumed, many of which are also at risk. Although outer coast Chinook samples included 14 stocks, four rivers systems accounted for over 90% of samples, predominantly the Columbia River. Increasing the abundance of Chinook salmon stocks that inhabit the whales’ winter range may be an effective conservation strategy for this population.

journals.plos.org/plosone/article?id=10.1371/journal.pone.0247031

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75 orcas hunt a 16 meter blue whale. After 3 hours, the whale finally perished.



EDIT: I'm assuming this-> is the same incident, given that it was published close to the day of the incident (March 16, 2021) and reports an incident in Bremer. But in this article, the biologist involved describes the blue whale as being "completely surrounded" by orcas, so it's obvious that many orcas were attacking it at the same time. In another article (link), we learn that groups of 6-8 orcas took turns ramming/pushing the whale for the first two hours (only drawing blood after three). So basically, once one group of orcas got exhausted trying to kill it, another group would take their place and continue the assault (eventually leading to the whale's death). Evidently, it takes a sh!t ton of effort for orcas to kill them.

Cathy Finch, a writer lucky enough to be aboard the ship during the rare phenomenon, reports for Australian Geographic that during the first two hours of the encounter groups of six to eight orcas would take turns pushing, bumping and ramming their quarry in attempts to drown the krill-feeding baleen whale while also herding it into shallower water so that it’s carcass couldn’t sink too deep for the predators to feed. When each group of orcas wore themselves out bullying the big blue with breaches and tail slaps at the surface, they would tag in a fresh band of killers and wait off in the margins while they regained their strength.

[Supercommunist]

^I feel that these accounts of large amounts of orcas taking a very long time to kill filter feeding whales discredits the idea that orcas would have dominated large, extinct, marine predators like megaladon.

I bet if they lived alongside the likes of meg, they would have been the aquatic equivalent of african wild dogs.

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There is one record of a large group of residents chasing and apparently attacking a small group of transients (Baird, 2000). There were approximately 13 resident orcas but only 3 transient orcas.

You know what they say, quantity is a quality of its own.

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Nice shots by Joel Sartore (link). These would make excellent profile pics (but I love my current one too much to change it).

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Humpbacks evidently do not like mammal-eating orcas (Pitman et al., 2017).

Humpback whales (Megaptera novaeangliae) are known to interfere with attacking killer whales (Orcinus orca). To investigate why, we reviewed accounts of 115 interactions between them. Humpbacks initiated the majority of interactions (57% vs. 43%; n = 72), although the killer whales were almost exclusively mammal-eating forms (MEKWs, 95%) vs. fish-eaters (5%; n = 108). When MEKWs approached humpbacks (n = 27), they attacked 85% of the time and targeted only calves. When humpbacks approached killer whales (n = 41), 93% were MEKWs, and ≥87% of them were attacking or feeding on prey at the time. When humpbacks interacted with attacking MEKWs, 11% of the prey were humpbacks and 89% comprised 10 other species, including three cetaceans, six pinnipeds, and one teleost fish. Approaching humpbacks often harassed attacking MEKWs (≥55% of 56 interactions), regardless of the prey species, which we argue was mobbing behavior. Humpback mobbing sometimes allowed MEKW prey, including nonhumpbacks, to escape. We suggest that humpbacks initially responded to vocalizations of attacking MEKWs without knowing the prey species targeted. Although reciprocity or kin selection might explain communal defense of conspecific calves, there was no apparent benefit to humpbacks continuing to interfere when other species were being attacked. Interspecific altruism, even if unintentional, could not be ruled out.

Of note in this study is that calves and juveniles may be regularly attacked, but adults are rarely targeted by orcas (no surprise there).

There is, however, mounting evidence to suggest that killer whales may in fact regularly attack humpbacks, and that calves and juveniles are the main targets (Chittleborough 1953, Katona et al. 1980, Whitehead and Glass 1985, Jefferson et al. 1991, Paterson and Paterson 2001, Baird et al. 2006, Reeves et al. 2006, Ford and Reeves 2008, Saulitis et al. 2015). In three separate studies (Naessig and Lanyon 2004, Mehta et al. 2007, Steiger et al. 2008), images from humpback whale photo-identification catalogs compiled from various studies around the world were analyzed for MEKW tooth rake marks on the flukes and used to infer the prevalence of killer whale attacks (keeping in mind that marked whales represent only the survivors of such attacks, Clapham 2001). Although the frequency of rake-mark occurrences in some populations ranged as high as 20%–40%, in the largest study (Mehta et al. 2007) less than 7% of whales acquired additional rake marks after the first time they were photographed. Based on similar findings, all three studies concluded that killer whales regularly attacked humpback calves and juveniles but rarely adults (Naessig and Lanyon 2004, Mehta et al. 2007, Steiger et al. 2008). Furthermore, these attacks could result in significant calf mortality. When Gabriele et al. (2001) compared the number of individually identified humpback mothers with calves on their North Pacific breeding grounds, with those found later without calves in the feeding areas, calf mortality during the first year of life was estimated to be approximately 18% (15%–24%), although the specific causes or locations of that mortality could not be identified.

Although MEKWs purportedly killed one humpback calf (#36) and possibly another (#10; neither kill was confirmed), no adult humpbacks were reported killed or seriously wounded during any of the interactions. Observers sometimes reported seeing exposed flesh, minor bleeding, or bits of skin and blubber floating on the surface during some of the attacks (#2, 3, 34, 47), but there was no evidence to suggest that any adult humpbacks sustained life-threatening wounds.

Our review supports previous conclusions that healthy adult humpback whales, because of their much larger size, sometimes combative nature, and robust appendages (see below), are probably immune to killer whale predation (Whitehead and Glass 1985, Jefferson et al. 1991, Mehta et al. 2007, Ford and Reeves 2008, Steiger et al. 2008, Pitman et al. 2015). Even lone humpbacks sometimes deliberately approached and interacted with groups of 10 or more MEKWs that were attacking various prey species (Table 1), and when MEKWs approached adult humpbacks without calves, the MEKWs left almost immediately. This confirms that any putative absence of predation pressure on humpback whales by MEKWs (Clapham 1996, 2001; Clapham and Mead 1999; Mehta et al. 2007) pertains only to healthy adult humpbacks, which presumably allows them to approach attacking MEKWs largely with impunity.

Although adult humpbacks may be safe from MEKW predation, subadults, juveniles, and especially calves are vulnerable to attack, and this probably applies to all species of large whales (Melnikov and Zagrebin 2005; Reeves et al. 2006; Ford and Reeves 2008; Pitman et al. 2007, 2015; Barrett-Lennard et al. 2011). As Scammon (1874) commented about killer whales, “it is but rarely these carnivora of the sea attack the larger Cetaceans, but chiefly prey with great rapacity upon their young.”

It may be that the humpback whale's great size (25-30 tonnes), coupled with its formidable pectoral flippers+tail flukes, makes it uniquely well suited to fighting off orcas in comparison to other mysticetes (and thus interfere with orcas in the act of predation on other animals).

The humpback whale is, to our knowledge, the only cetacean that deliberately approaches attacking MEKWs and can drive them off, although southern right whales (Eubalaena australis) may also group together to fend off MEKWs attacking other right whales (Sironi et al. 2008). The adult humpback's enormous body size certainly contributes to its apparent invulnerability, but there are other, larger whale species that are not known to deliberately approach MEKWs. We suggest that the evolution of the humpback's massive pectoral flippers may have given it an advantage over killer whales and perhaps altered the balance of power in their interactions.

Humpback flippers (Fig. 3) can measure up to 5 m long, one third of their total body length (Woodward et al. 2006), and can weigh over 1 ton (1,016 kg, Tomilin 1967). Although they are by far the largest cetacean flippers, both relatively and absolutely, they are quite flexible and maneuverable, and humpbacks can wield them adroitly (Edel and Winn 1978). Furthermore, in addition to sheer impact power, each flipper has a knobby leading edge often encrusted with large, sharp, sessile barnacles (Coronula spp.) that can tear the flesh of their opponents (Pierroti et al. 1985, Ford and Reeves 2008). These formidable appendages provide protection at the anterior end of the whale, and, when used in concert with the flukes, afford humpbacks with fore and aft, offensive and defensive weaponry—a capability that is unique among living baleen whales. When humpbacks are agitated by killer whales, they appear to randomly flail their flippers and flukes without specifically targeting individual attackers. Nevertheless, killer whales appear to recognize the danger and normally remain “at arm's-length” when interacting with humpbacks (RLP, personal observation)

Jefferson et al. (1991) also recount several antagonistic interactions between orcas and humpback whales. One is a whaler record dating to 1830 of a single orca killing a humpback. Jefferson et al. deem this record to be possibly unreliable (there's an asterisk next to the description that denotes a "Possibly unreliable record"; for what it's worth Ford & Reeves (2008) actually point out that most of the accounts in this review were second-hand, anecdotal, and incomplete). Given that even lone humpbacks will approach pods of 10+ orcas, and that the dolphins will retreat almost immediately from a humpback without a calf, I'm inclined to agree with Jefferson et al.'s assessment at the very least (unless this humpback was crippled in some manner).

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One thing I'd really love to see is a formal decision as to whether or not the different orca ecotypes should be reclassified as multiple species. No one has really done any revision of orca taxonomy yet, but while they're all classified as one species for now, it seems like this could plausibly change in the future.

Here are a couple genomic studies that support hypotheses of there being multiple species, for whatever they're worth. They're from a while back, so idk if we've learned anything since then.

LeDuc et al. (2008)

Recently, three visually distinct forms of killer whales (Orcinus orca) were described from Antarctic waters and designated as types A, B and C. Based on consistent differences in prey selection and habitat preferences, morphological divergence and apparent lack of interbreeding among these broadly sympatric forms, it was suggested that they may represent separate species. To evaluate this hypothesis, we compared complete sequences of the mitochondrial control region from 81 Antarctic killer whale samples, including 9 type A, 18 type B, 47 type C and 7 type-undetermined individuals. We found three fixed differences that separated type A from B and C, and a single fixed difference that separated type C from A and B. These results are consistent with reproductive isolation among the different forms, although caution is needed in drawing further conclusions. Despite dramatic differences in morphology and ecology, the relatively low levels of sequence divergence in Antarctic killer whales indicate that these evolutionary changes occurred relatively rapidly and recently.

Morin et al. (2010)

Killer whales (Orcinus orca) currently comprise a single, cosmopolitan species with a diverse diet. However, studies over the last 30 yr have revealed populations of sympatric ‘‘ecotypes’’ with discrete prey preferences, morphology, and behaviors. Although these ecotypes avoid social interactions and are not known to interbreed, genetic studies to date have found extremely low levels of diversity in the mitochondrial control region, and few clear phylogeographic patterns worldwide. This low level of diversity is likely due to low mitochondrial mutation rates that are common to cetaceans. Using killer whales as a case study, we have developed a method to readily sequence, assemble, and analyze complete mitochondrial genomes from large numbers of samples to more accurately assess phylogeography and estimate divergence times. This represents an important tool for wildlife management, not only for killer whales but for many marine taxa. We used high throughput sequencing to survey whole mitochondrial genome variation of 139 samples from the North Pacific, North Atlantic, and southern oceans. Phylogenetic analysis indicated that each of the known ecotypes represents a strongly supported clade with divergence times ranging from ~150,000 to 700,000 yr ago. We recommend that three named ecotypes be elevated to full species, and that the remaining types be recognized as subspecies pending additional data. Establishing appropriate taxonomic designations will greatly aid in understanding the ecological impacts and conservation needs of these important marine predators. We predict that phylogeographic mitogenomics will become an important tool for improved statistical phylogeography and more precise estimates of divergence times.

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Yeesh. Looks like this orca rammed another one too hard. Also suggests that the extinct squalodonts, with their much more gracile skulls, were highly unlikely to have rammed larger prey without fatally injuring themselves.

Thus, the tooth morphology of Squalodon suggests a diverse, opportunistic diet, similar to that of the modem Orcinus. However, a comparison of the skull morphology of various cetaceans may also reveal aspects of squalodont diet. In Figure 5.5, several cetacean skulls are shown in dorsal view, all to the same scale. Note in particular the robustness of Orcinus and Pseudorca compared to both species of Squalodon. It is possible that the two modern species require larger skulls because they attack animals considerably larger than themselves. Orcinus is known to prey on all the mysticetes except Caperea, as well as Physeter (Hoyt, 1990). Yet even with its massive skull, Orcinus is still vulnerable to breakage at  the base of the rostrum, as indicated by an incident at a marine park in 1989. In this case, one killer whale rammed another, breaking the rostrum of the attacker at the base and causing the attacker to bleed to death (Hoyt, 1990). Given the much more gracile squalodont skull, it seems very unlikely that these whales could attack animals larger than themselves without running a serious risk of fatal injury.

digitalcommons.lsu.edu/cgi/viewcontent.cgi?article=7824&context=gradschool_disstheses

[Supercommunist]

Grey whale killed by orcas after a six hour hunt:

www.reddit.com/r/HardcoreNature/comments/otrflb/aftermath_of_orca_orcinus_orca_predation_on_grey/

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Bloody female elephant seal hunt. Holy Christ.