Orca (Killer Whale) – Orcinus orca

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Two adult grey whales fended off 30 orcas over a six hour period.

[Creodont]

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Unraveling the enigmatic type D killer whale (Orcinus orca): mass stranding in the Magellan Strait, Chile

There are different ecotypes of killer whales (Orcinus orca) worldwide; type D killer whales are the least known. These killer whales have a globose head, an extremely small post-ocular patch and a falcate dorsal fin. We report the first stranding event of type D killer whales recorded in southern South America, in the Magellan Strait, Chile. The group consisted of four adult females, two juvenile females, and two females and one male of indeterminate age class. Total length of adult females averaged 572.8 ± 23.6 cm and juvenile females averaged 397.0 ± 24.0 cm. Dorsal fin height of adult females averaged 57.3 ± 8.5 cm and in juvenile females 30.5 ± 19.1 cm. No obvious signs of anthropogenic intervention were observed. The characteristic small post-ocular white eye patch of this killer whale ecotype measured 21.8 cm long and 5.9 cm wide in the freshest carcass found. All animals presented backswept dorsal fins and a dental formula of 11 to 13 maxillary and mandibular teeth. The length of the largest tooth in each individual ranged from 8.0 to 10.2 cm, suggesting that type D killer whales have smaller teeth. We suggest that the total length of type D killer whales is shorter than other killer whale ecotypes. After 67 years, we report the second known stranding of type D killer whales worldwide and we report for the first time body measurements, size, and number of teeth of this ecotype of killer whales.

link.springer.com/article/10.1007/s00300-023-03156-2

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The incidence of bent dorsal fins in free‐ranging cetaceans

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.

While bent dorsal fins are displayed worldwide in a relatively high number of free‐ranging cetacean species, such deformities or disfigurements are still rare in nature. In general, these animals represent < 1% of their populations, with the exception of P. crassidens and O. orca, based on records from this study and the relevant literature (see Table 2). Our literature review shows that this anomaly is rarely reported. For example, Visser (1998) compared the proportion of abnormal fins in adult males of O. orca from New Zealand (23.3%) with that in the resident population from British Columbia (4.7%) and from Norway (0.6%). Baird & Gorgone (2005) found < 1% of disfigured fins (including fins that were missing or bent over) from several populations of odontocetes, consistent with the proportion presented here, although 3.5% of false killer whales from the main Hawaiian Islands population have such disfigurements. Guerrero‐Ruiz et al. (2005) found that only four in > 1000 resident O. orca and two of > 300 transients from Alaska to Mexico had completely collapsed dorsal fins. Discrepancies in the proportion of abnormal fins (e.g. high values from New Zealand) could be explained by definitions given for bending between studies (i.e. to differences in how much of an angle is required in order to be classified as bent or unbent, or due to including other forms of malformation), making it difficult to compare species and areas. Despite such differences, the highest occurrence of bending was observed in apex predators P. crassidens and O. orca (Table 2). In the case of the former species, all known‐sexed individuals with bent dorsal fins were adult females, whereas in the latter species this was mainly represented by adult males (91%; based on 58 adults of known sex).

www.ncbi.nlm.nih.gov/pmc/articles/PMC5770300/

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Postreproductive female killer whales reduce socially inflicted injuries in their male offspring

Understanding the evolution of menopause presents a long-standing scientific challenge—why should females cease ovulation prior to the end of their natural lifespan? In human societies, intergenerational resource transfers, for example, food sharing and caregiving, are thought to have played a key role in the evolution of menopause, providing a pathway by which postreproductive females can boost the fitness of their kin. To date however, other late-life contributions that postreproductive females may provide their kin have not been well studied. Here, we test the hypothesis that postreproductive female resident killer whales (Orcinus orca) provide social support to their offspring by reducing the socially inflicted injuries they experience. We found that socially inflicted injuries, as quantified by tooth rake marks, are lower for male offspring in the presence of their postreproductive mother. In contrast, we find no evidence that postreproductive mothers reduce rake marking in their daughters. Similarly, we find no evidence that either reproductive mothers or grandmothers (reproductive or postreproductive) reduce socially inflicted injuries in their offspring and grandoffspring, respectively. Moreover, we find that postreproductive females have no effect on reducing the rake marks for whales in their social unit who are not their offspring. Taken together, our results highlight that directing late-life support may be a key pathway by which postreproductive females transfer social benefits to their male offspring.

www.cell.com/current-biology/fulltext/S0960-9822(23)00824-2?fbclid=IwAR2XWjKNK_r5mq0fOkOLV8H6yqaFl-Wfp6j9AmLCAEAy7tz2SraDP2-xAHM_aem_AYf6RxPw3Nn5u_S4RlbvS3XRod9i6d6MRww1lIT-yrljXmBnu14yyZQE-SN6w0l8CtA&mibextid=Zxz2cZ

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Ancestry testing of “Old Tom,” a killer whale central to mutualistic interactions with human whalers

Cooperative hunting between humans and killer whales (Orcinus orca) targeting baleen whales was reported in Eden, New South Wales, Australia, for almost a century. By 1928, whaling operations had ceased, and local killer whale sightings became scarce. A killer whale from the group, known as “Old Tom,” washed up dead in 1930 and his skeleton was preserved. How these killer whales from Eden relate to other populations globally and whether their genetic descendants persist today remains unknown. We extracted and sequenced DNA from Old Tom using ancient DNA techniques. Genomic sequences were then compared with a global dataset of mitochondrial and nuclear genomes. Old Tom shared a most recent common ancestor with killer whales from Australasia, the North Atlantic, and the North Pacific, having the highest genetic similarity with contemporary New Zealand killer whales. However, much of the variation found in Old Tom’s genome was not shared with these widespread populations, suggesting ancestral rather than ongoing gene flow. Our genetic comparisons also failed to find any clear descendants of Tom, raising the possibility of local extinction of this group. We integrated Traditional Custodian knowledge to recapture the events in Eden and recognize that Indigenous Australians initiated the relationship with the killer whales before European colonization and the advent of commercial whaling locally. This study rectifies discrepancies in local records and provides new insight into the origins of the killer whales in Eden and the history of Australasian killer whales.

academic.oup.com/jhered/advance-article/doi/10.1093/jhered/esad058/7308443?login=false

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Revised taxonomy of eastern North Pacific killer whales (Orcinus orca): Bigg’s and resident ecotypes deserve species status

Killer whales (Orcinus orca) are currently recognized as a single ecologically and morphologically diverse, globally distributed species. Multiple morphotypes or ecotypes have been described, often associated with feeding specialization, and several studies have suggested taxonomic revision to include multiple subspecies or species in the genus. We review the ecological, morphological and genetic data for the well-studied ‘resident’ and Bigg’s (aka ‘transient’) ecotypes in the eastern North Pacific and use quantitative taxonomic guidelines and standards to determine whether the taxonomic status of these killer whale ecotypes should be revised. Our review and new analyses indicate that species-level status is justified in both cases, and we conclude that eastern North Pacific Bigg’s killer whales should be recognized as Orcinus rectipinnus (Cope in Scammon, 1869) and resident killer whales should be recognized as Orcinus ater (Cope in Scammon, 1869).

royalsocietypublishing.org/doi/10.1098/rsos.231368

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I found something potentially interesting.

In June 1960, an orca beached itself on Great Abaco in the Bahamas. It had several open wounds in the tail region and was followed inshore by large sharks. The orca's dimensions definitely indicate an adult, but what I'm really interested in is what could have possibly caused the injuries.


archive.org/details/sim_journal-of-mammalogy_1961-08_42_3/page/418/mode/2up?view=theater

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Harassment and killing of porpoises (“phocoenacide”) by fish-eating Southern Resident killer whales (Orcinus orca)

Endangered Southern Resident killer whales (Orcinus orca) are fish-eaters that preferentially prey on adult Chinook salmon (Oncorhynchus tshawytscha). Despite being salmon specialists, individuals from all three killer whale pods (J, K, L) have been observed harassing and killing porpoises (family Phocoenidae) without consuming them. Retrospectively, we identified and analyzed 78 episodes of Southern Resident killer whales harassing porpoises between 1962 and 2020, of which 28 resulted in the porpoise's death (“phocoenacide”). Fifty-six episodes involved harbor porpoise (Phocoena phocoena), 13 involved Dall's porpoise (Phocoenoides dalli), and the porpoise species was unreported for nine episodes. Southern Resident killer whales often targeted young porpoises that were similar in size to adult Chinook salmon. Both sexes participated in porpoise harassment. Juveniles engaged in the behavior the most; however, their rates of engagement were not found to differ significantly from most other age classes. The behavior was passed through generations and social groupings, as it was first observed in L pod and spread to the other two pods. Killer whales are highly complex animals known to exhibit social learning and cultural transmission of learned behaviors, but the reason(s) for this behavior is unknown. Hypotheses include the social and developmental benefits of play, hunting practice, or displaced epimeletic behavior.

onlinelibrary.wiley.com/doi/pdfdirect/10.1111/mms.13073