Orca (Killer Whale) – Orcinus orca

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Only record of a human being attacked by an orca in the wild.

orcazine.com/in-the-jaws-of-an-orca/

[elosha11]

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Very recent paper on killer whales hunting blue whales. I emailed one of the authors to see if they would be willing to send me the full paper.

onlinelibrary.wiley.com/doi/10.1111/mms.12906

EDIT: Success. I can send the PDF to anyone interested.

[Supercommunist]

I'd like a copy.

[Infinity Blade]

Okay, I tried emailing it to you. Let me know if you've got it.

[Supercommunist]

Got it thanks.

[elosha11]

Jan 25, 2022 1:35:16 GMT 5 Infinity Blade said:

Very recent paper on killer whales hunting blue whales. I emailed one of the authors to see if they would be willing to send me the full paper.

onlinelibrary.wiley.com/doi/10.1111/mms.12906

EDIT: Success. I can send the PDF to anyone interested.

Can you send to me? Thanks.

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Sent. Let me know if you got it.

[elosha11]

^Got it, thanks.

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Looks like killer whales only became mammal-eaters relatively recently.

The origins of the killer whale ecomorph

The killer whale (Orcinus orca) and false killer whale (Pseudorca crassidens) are the only extant cetaceans that hunt other marine mammals, with pods of the former routinely preying on baleen whales >10 m in length and the latter being known to take other delphinids. Fossil evidence for the origins of this feeding behavior is wanting, although molecular phylogenies indicate that it evolved independently in the two lineages. We describe a new extinct representative of the killer whale ecomorph, Rododelphis stamatiadisi, based on a partial skeleton from the Pleistocene of Rhodes (Greece). Five otoliths of the bathypelagic blue whiting Micromesistius poutassou are associated with the holotype, providing unexpected evidence of its last meal. The evolutionary relationships of R. stamatiadisi and the convergent evolution of killer whale-like features were explored through a broad-ranging phylogenetic analysis that recovered R. stamatiadisi as the closest relative of P. crassidens and O. orca as the only living representative of a once diverse clade. Within the clade of Orca and kin, key features implicated in extant killer whale feeding, such as body size, tooth size, and tooth count, evolved in a stepwise manner. The tooth wear in Rododelphis and an extinct species of Orcinus (O. citoniensis) are consistent with a fish-based diet, supporting an exaptative Pleistocene origin for marine mammal hunting in both lineages. If correct, predation by the ancestors of Pseudorca and Orca did not play a significant role in the evolution of baleen whale gigantism.

www.sciencedirect.com/science/article/abs/pii/S0960982222002639

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Review of killer whale predation on large whales by a blogger. Pretty much what I expected: these last two paragraphs sum it up pretty well.

Another big question is what influence mammal-eating killer whales have on the population dynamics of mature individuals. It has been long-believed that calf mortalities to killer whales was a huge selection pressure in driving the distributions and migration routes of large whale species (6,13). By contrast, I don’t think the direct hunting of mature baleen whales has a strong ecological impact. I believe that the killer whale’s effect on populations of large whales is primarily on the immature cohort as most sources show that juveniles and calves make up the majority of documented kills for species larger than minkes (6,13,23,24,25,26). These findings are also supported by studies where the vast majority of individuals within observed baleen whale species receive their rake marks as calves and only a minority receive new ones over time (35,36). Even the adults that are killed are smaller than average, like the 20-meter blue whale or the 15-16 meter fin whale. It is very likely that Antarctic blue whales, where the average adult is 25-meters long and twice as heavy as the recently-documented pygmy, is virtually immune to killer whales.

Nonetheless, the current research still shows we’ve been underestimating killer whales and the impact that they do have on immature baleen whales. Which may be a concern for bowhead whales, as loss of sea ice in the Arctic is increasing the frequency of attacks on calves and juveniles. Without the ice, killer whales are able to remain in Arctic waters for longer periods of time (23,24,25). It’s also not outside the realm of possibility that other baleen whales will become increasingly vulnerable from poor health conditions due to climate change or net entanglements, echoing this previously unseen great white shark attack on a juvenile humpback (7). Killer whale predation can be a potentially large threat to recovering whale populations when compounded with anthropogenic influences.

callmejoe3.wordpress.com/2022/05/08/the-toughest-in-the-ocean-a-review-of-killer-whale-predation-of-large-whales/

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“Type D” killer whale genomes reveal long-term small population size and low genetic diversity

Genome sequences can reveal the extent of inbreeding in small populations. Here, we present the first genomic characterization of type D killer whales, a distinctive eco/morphotype with a circumpolar, subantarctic distribution. Effective population size is the lowest estimated from any killer whale genome and indicates a severe population bottleneck. Consequently, type D genomes show among the highest level of inbreeding reported for any mammalian species (FROH ≥ 0.65). Detected recombination cross-over events of different haplotypes are up to an order of magnitude rarer than in other killer whale genomes studied to date. Comparison of genomic data from a museum specimen of a type D killer whale that stranded in New Zealand in 1955, with 3 modern genomes from the Cape Horn area, reveals high covariance and identity-by-state of alleles, suggesting these genomic characteristics and demographic history are shared among geographically dispersed social groups within this morphotype. Limitations to the insights gained in this study stem from the nonindependence of the 3 closely related modern genomes, the recent coalescence time of most variation within the genomes, and the nonequilibrium population history which violates the assumptions of many model-based methods. Long-range linkage disequilibrium and extensive runs of homozygosity found in type D genomes provide the potential basis for both the distinctive morphology, and the coupling of genetic barriers to gene flow with other killer whale populations.

academic.oup.com/jhered/advance-article/doi/10.1093/jhered/esac070/7086686?login=false

[Creodont]

[Creodont]

A pod of orcas works together to corral a school of mobula rays. (Baja California, Mexico)