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Killer whale predation on an Antarctic minke whale in the northern Antarctic Peninsula

Abstract

We describe the seldom observed event of a group of type A killer whale (Orcinus orca) predating on an Antarctic minke whale (Balaenoptera bonaerensis) in austral summer 2019. A pod of 11-13 individuals was observed – and documented by photographs and video – as they killed and fed on the minke whale in the Bransfield Strait, northern Antarctic Peninsula. The pod was being observed for about one hour, when some killer whale’s individuals were noticed to be performing hunting behaviour. This lasted about 10 minutes, at the end of which the minke whale was killed. Three different species of seabirds were observed feeding on the minke carcass. A video of the encounter is provided.

Key words
Balaenoptera bonaerensis; Orcinus orca; Predator; Southern Ocean; Type A killer whale diet

Killer whale (Orcinus orca) is a cosmopolitan species with a carnivorous diet (Ford 2019FORD JKB. 2019. Killer whales: Behavior, social organization, and ecology of the oceans’ apex predators. In: Würsig B(Ed), Ethology and behavioral ecology of marine mammals, Springer, p. 234-259.). At present, there are five ecotypes of killer whales described in the Southern Ocean: A, B1, B2, C, and D, which are classified based on their size, pigmentation patterns, diet, and genetics (Pitman & Ensor 2003PITMAN RL & ENSOR P. 2003. Three forms of killer whales (Orcinus orca) in Antarctic waters. J Cetacean Res Manag 5: 131-139., Morin et al. 2010MORIN PA ET AL. 2010. Complete mitochondrial genome phylogeographic analysis of killer whales (Orcinus orca) indicates multiple species. Genome Res 20(7): 908-916., Pitman et al. 2020aPITMAN RL, BALLANCE LT, SIRONI M, TOTTERDELL J, TOWERS JR & WELLARD R. 2020a. Enigmatic megafauna: type D killer whale in the Southern Ocean. Ecology 101(1): e02871.). The sympatric forms B1 and B2 are differentiated from the others concerning physical (size and pigmentation) and ecological (diet) aspects (Durban et al. 2017DURBAN JW, FEARNBACH H, BURROWS DG, YLITALO GM & PITMAN RL. 2017. Morphological and ecological evidence for two sympatric forms of Type B killer whale around the Antarctic Peninsula. Polar Biol 40: 231-236.). Type B1 hunting behaviour and prey-selectivity in the Antarctic Peninsula have been described by a few authors and reports mostly include hunting of phocids on ice floes, occasionally penguins and rarely baleen whales (Smith et al. 1981SMITH TG, SINIFF DB, REICHLE R & STONE S. 1981. Coordinated behaviour of killer whales, Orcinus orca, hunting a crabeater seal, Lobodon carcinophagus. Can J Zool 59: 1185-1189., Visser et al. 2008VISSER IN, SMITH TG, BULLOCK ID, GREEN GD, CARLSSON OG & IMBERTI S. 2008. Antarctic peninsula killer whales (Orcinus orca) hunt seals and a penguin on floating ice. Mar Mammal Sci 24: 225-234., Pitman & Durban 2012PITMAN RL & DURBAN JW. 2012. Cooperative hunting behaviour, prey selectivity and prey handling by pack ice killer whales (Orcinus orca), type B, in Antarctic Peninsula waters. Mar Mammal Sci 28: 16-36.). The diet from Type B2 can include Patagonian toothfish (Dissostichus eleginoides) (Pitman & Durban 2010PITMAN RL & DURBAN JW. 2010. Killer whale predation on penguins in Antarctica. Polar Biol 33: 1589–1594., Tixier et al. 2019TIXIER P, GIMÉNEZ J, REISINGER RR, MÉNDEZ-FERNANDEZ P, ARNOULD JP, CHEREL Y & GUINET C. 2019. Importance of toothfish in the diet of generalist subantarctic killer whales: implications for fisheries interactions. Mar Ecol Prog Ser 613: 197-210.; Towers et al. 2019TOWERS JR, TIXIER P, ROSS KA, BENNETT J, ARNOULD JP, PITMAN RL & DURBAN JW. 2019. Movements and dive behaviour of a toothfish-depredating killer and sperm whale. ICES J Mar Sci 76(1): 298-311.), other fish and squid (Pitman et al. 2020bPITMAN RL, DURBAN JW, JOYCE T, FEARNBACH H, LAURIANO G & PANIGADA S. 2020b. Skin in the game: Epidermal molt as a driver of long-distance migration. Mar Mammal Sci 36(2): 565-594.), pygoscelid penguins (Pitman & Durban 2010PITMAN RL & DURBAN JW. 2010. Killer whale predation on penguins in Antarctica. Polar Biol 33: 1589–1594.), and does not seem to include marine mammals (Durban et al. 2017DURBAN JW, FEARNBACH H, BURROWS DG, YLITALO GM & PITMAN RL. 2017. Morphological and ecological evidence for two sympatric forms of Type B killer whale around the Antarctic Peninsula. Polar Biol 40: 231-236.). Type C killer whales have been reported to feed on fish in the Ross Sea (Pitman et al. 2018PITMAN RL, FEARNBACH H & DURBAN JW. 2018. Abundance and population status of Ross Sea killer whales (Orcinus orca, type C) in McMurdo Sound, Antarctica: evidence for impact by commercial fishing? Polar Biol 41: 781-92.). Type D individuals are the least known, but their diet seems to include demersal fish including Patagonian toothfish (Pitman et al. 2020a). As for type A individuals, there is also limited information available, but a few reports suggest potential migrations in pursuit of Antarctic minke whales (Balaenoptera bonaerensis), Arnoux’s beaked whales (Berardius arnuxii), and southern elephant seals (Mirounga leonina) (Pitman & Ensor 2003PITMAN RL & ENSOR P. 2003. Three forms of killer whales (Orcinus orca) in Antarctic waters. J Cetacean Res Manag 5: 131-139., Fearnbach et al. 2019FEARNBACH H, DURBAN JW, ELLIFRIT DK & PITMAN RL. 2019. Abundance of Type A killer whales (Orcinus orca) in the coastal waters off the western Antarctic Peninsula. Polar Biol 42: 1477-1488.). Type A individuals have been recorded attacking and killing Antarctic minke whales in the Gerlache Strait, Antarctica, with images available from the BBC tv series Frozen Planet (2011) and some descriptions by Berlowitz & Fothergill (2011)BERLOWITZ V & FOTHERGILL A. 2011. Frozen planet: A world beyond imagination, BBC Books, 312 p..

On the 30th January 2019, a pod of type A killer whales was sighted at 63.06°S and 58.78°W (185 m water depth) during a line transect survey for cetacean distribution and abundance in the Bransfield Strait as part of research activities of the Brazilian Antarctic Program. We based the identification of the ecotype on external characteristics as the lack of a visible dorsal cape and the size and oval and elongated eyepatches (Pitman & Ensor 2003PITMAN RL & ENSOR P. 2003. Three forms of killer whales (Orcinus orca) in Antarctic waters. J Cetacean Res Manag 5: 131-139.) (Figure 1 and video footage in Additional File, available at https://mega.nz/folder/VjMhka6I#7KJGqj2xcguvIIbVQIXwdA). The individuals were divided into two sub-groups, one composed of an adult male and three females or large juveniles, and the other group consisted of two adult males and another five to seven females or large juveniles. The effort was halted, and the sub-groups were approached for the collection of photo-identification data (using a Nikon D300 digital camera with 80-400 mm lens).

Figure 1
Some of the Type A killer whales of the pod observed predating on an Antarctic minke whale in Antarctica in austral summer 2019.

The killer whales were photographed from about 200-300 m for about 40 minutes with no signs of hunting behaviour. After the collection of photo-identification data, the vessel started to move away from the pod and, suddenly, two animals were sighted performing hunting behaviour (speeding and displaying porpoising movements); after 8-12 minutes, likely a juvenile (judged by the estimated length, 5-6 meters, in comparison to the sizes of the killer whales; Durban et al. 2021DURBAN JW, FEARNBACH H, PAREDES A, HICKMOTT LS & LEROI DJ. 2021. Size and body condition of sympatric killer whale ecotypes around the Antarctic Peninsula. Mar Ecol Prog Ser 677: 209-217.) Antarctic minke whale was observed porpoising out of the water and swimming fast as the animal was chased by two killer whales. The minke whale was hit out of the water by a killer whale three times, knocked out of the water on all occasions (Fig. 2). This tactic seems to be common during predation of large cetaceans, including minke whales (Jefferson et al. 1991JEFFERSON TA, STACEY PJ & BAIRD RW. 1991. A review of Killer Whale interactions with other marine mammals: predation to co-existence. Mammal Rev 21: 151-180., Ford et al. 2005FORD JKB, ELLIS GM, MATKIN DR, BALCOMB KC, BRIGGS D & MORTON AB. 2005. Killer whale attacks on minke whales: prey capture and antipredator tactics. Mar Mammal Sci 21: 603-618., Ford & Reeves 2008FORD JK & REEVES RR. 2008. Fight or flight: antipredator strategies of baleen whales. Mamm Rev 38(1): 50-86.; Samarra et al. 2018SAMARRA FI ET AL. 2018. Prey of killer whales (Orcinus orca) in Iceland. PloS ONE 13: e0207287.). After the last hit, the minke whale was not observed at the surface again and the killer whales kept diving around the attack area. The blubber odour, oil slick and bits of tissue at the surface were used as clues to assume that the whale was dead (Pitman & Durban 2012PITMAN RL & DURBAN JW. 2012. Cooperative hunting behaviour, prey selectivity and prey handling by pack ice killer whales (Orcinus orca), type B, in Antarctic Peninsula waters. Mar Mammal Sci 28: 16-36.). Based on the size of the dorsal fin, the attack was performed by females or juvenile males’ killer whales of the bigger sub-group - different from the role of males in fatal attacks as reported in other occasions (e.g. Pitman et al. 2023PITMAN RL, SCHULMAN-JANIGER A, GUERRERO-RUIZ ME, ORTEGA-GONZALEZ AM, ROSALES-NANDUCA H, FISHBACH M, PACE R, RODRIGUES R, CHEVALLAY D & VILORIA-GÓMORA L. 2023. Records of fatal killer whale (Orcinus orca) attacks on fin whales (Balaenoptera physalus) with an emphasis on Baja California, Mexico. Aquat Mamm 49(2): 195-207.). However, after the attack, the sub-groups got together to feed on the carcass, including the males.

Figure 2
Antarctic minke whale being rammed and knocked out of the water by a killer whale. This sequence (a-c) is taken from the footage recorded during the attack registered in Antarctica in austral summer 2019 (Additional File available at https://mega.nz/folder/VjMhka6I#7KJGqj2xcguvIIbVQIXwdA).

Just after the attack, some individuals of four seabird species were observed associated with the killer whales. Among these seabird species, southern giant petrels (Macronectes giganteus) (2 individuals) - including one white morph individual, snow petrel (Pagodrama nivea) (1-2 individuals), Wilson’s storm petrels (Oceanites oceanicus) (1-3 individuals), and Cape petrels (Daption capense) (3-5 individuals) were observed. Some of them fed on the prey scraps, chasing each other on some occasions. A killer whale swam off with a large prey scrap that a giant petrel had been feeding on.

The encounter lasted approximately one hour, including the approximately 10 minutes of killer whales observed hunting behaviour. The attack and killing lasted nearly one minute and it took another 10 minutes for the killer whales to feed on the carcass. From there, as the weather conditions started to deteriorate, the vessel resumed its route. The pictures obtained were included in the Antarctic killer whale photo-identification catalogue to look for potential further information related to the individuals of the pod. Matches were found for ten individuals, for which previous records go back up to 2009 and include other sightings in the Bransfield Strait, and in the Gerlache Strait. It could also be noted that individuals are not necessarily always observed together. The event was video recorded (Additional File, available at https://mega.nz/folder/VjMhka6I#7KJGqj2xcguvIIbVQIXwdA) and can contribute to the knowledge of the feeding habits and hunting behaviour of type A killer whales in the Antarctic Peninsula or be of interest to citizen science as well.

ACKNOWLEDGMENTS

We would like to thank the captain and all crew of the NPo Almirante Maximiliano of the Brazilian Navy that supported our work during the cruise in January-February 2019 as part of the XXXVIII Brazilian Antarctic Operation. Special thanks to Flavio Cruz for his efforts in recording the observed event and for sharing all the material with us. We are grateful to Holly Fearnbach and John Durban for working with the images uploaded into the Antarctic killer whale photo-identification catalogue and sharing information on the matching individuals found. Financial support was provided by CNPq (National Council for Research and Development) and CAPES (Coordination for the Improvement of Higher Education Personnel). This work is a contribution of the Grupo de Oceanografia de Altas Latitudes – GOAL/High Latitudes Oceanography Group activities in the Brazilian Antarctic Program (PROANTAR) and the research group Ecologia e Conservação da Megafauna Marinha-EcoMega/CNPq, under the Antarctic Research Projects INTERBIOTA (CNPq grant number 407889/2013-2). We also thank the reviewers for their contributions to improve the quality of this work.

REFERENCES

  • BERLOWITZ V & FOTHERGILL A. 2011. Frozen planet: A world beyond imagination, BBC Books, 312 p.
  • DURBAN JW, FEARNBACH H, BURROWS DG, YLITALO GM & PITMAN RL. 2017. Morphological and ecological evidence for two sympatric forms of Type B killer whale around the Antarctic Peninsula. Polar Biol 40: 231-236.
  • DURBAN JW, FEARNBACH H, PAREDES A, HICKMOTT LS & LEROI DJ. 2021. Size and body condition of sympatric killer whale ecotypes around the Antarctic Peninsula. Mar Ecol Prog Ser 677: 209-217.
  • FEARNBACH H, DURBAN JW, ELLIFRIT DK & PITMAN RL. 2019. Abundance of Type A killer whales (Orcinus orca) in the coastal waters off the western Antarctic Peninsula. Polar Biol 42: 1477-1488.
  • FORD JKB, ELLIS GM, MATKIN DR, BALCOMB KC, BRIGGS D & MORTON AB. 2005. Killer whale attacks on minke whales: prey capture and antipredator tactics. Mar Mammal Sci 21: 603-618.
  • FORD JK & REEVES RR. 2008. Fight or flight: antipredator strategies of baleen whales. Mamm Rev 38(1): 50-86.
  • FORD JKB. 2019. Killer whales: Behavior, social organization, and ecology of the oceans’ apex predators. In: Würsig B(Ed), Ethology and behavioral ecology of marine mammals, Springer, p. 234-259.
  • JEFFERSON TA, STACEY PJ & BAIRD RW. 1991. A review of Killer Whale interactions with other marine mammals: predation to co-existence. Mammal Rev 21: 151-180.
  • MORIN PA ET AL. 2010. Complete mitochondrial genome phylogeographic analysis of killer whales (Orcinus orca) indicates multiple species. Genome Res 20(7): 908-916.
  • PITMAN RL, BALLANCE LT, SIRONI M, TOTTERDELL J, TOWERS JR & WELLARD R. 2020a. Enigmatic megafauna: type D killer whale in the Southern Ocean. Ecology 101(1): e02871.
  • PITMAN RL & DURBAN JW. 2010. Killer whale predation on penguins in Antarctica. Polar Biol 33: 1589–1594.
  • PITMAN RL & DURBAN JW. 2012. Cooperative hunting behaviour, prey selectivity and prey handling by pack ice killer whales (Orcinus orca), type B, in Antarctic Peninsula waters. Mar Mammal Sci 28: 16-36.
  • PITMAN RL, DURBAN JW, JOYCE T, FEARNBACH H, LAURIANO G & PANIGADA S. 2020b. Skin in the game: Epidermal molt as a driver of long-distance migration. Mar Mammal Sci 36(2): 565-594.
  • PITMAN RL & ENSOR P. 2003. Three forms of killer whales (Orcinus orca) in Antarctic waters. J Cetacean Res Manag 5: 131-139.
  • PITMAN RL, FEARNBACH H & DURBAN JW. 2018. Abundance and population status of Ross Sea killer whales (Orcinus orca, type C) in McMurdo Sound, Antarctica: evidence for impact by commercial fishing? Polar Biol 41: 781-92.
  • PITMAN RL, SCHULMAN-JANIGER A, GUERRERO-RUIZ ME, ORTEGA-GONZALEZ AM, ROSALES-NANDUCA H, FISHBACH M, PACE R, RODRIGUES R, CHEVALLAY D & VILORIA-GÓMORA L. 2023. Records of fatal killer whale (Orcinus orca) attacks on fin whales (Balaenoptera physalus) with an emphasis on Baja California, Mexico. Aquat Mamm 49(2): 195-207.
  • SAMARRA FI ET AL. 2018. Prey of killer whales (Orcinus orca) in Iceland. PloS ONE 13: e0207287.
  • SMITH TG, SINIFF DB, REICHLE R & STONE S. 1981. Coordinated behaviour of killer whales, Orcinus orca, hunting a crabeater seal, Lobodon carcinophagus. Can J Zool 59: 1185-1189.
  • TIXIER P, GIMÉNEZ J, REISINGER RR, MÉNDEZ-FERNANDEZ P, ARNOULD JP, CHEREL Y & GUINET C. 2019. Importance of toothfish in the diet of generalist subantarctic killer whales: implications for fisheries interactions. Mar Ecol Prog Ser 613: 197-210.
  • TOWERS JR, TIXIER P, ROSS KA, BENNETT J, ARNOULD JP, PITMAN RL & DURBAN JW. 2019. Movements and dive behaviour of a toothfish-depredating killer and sperm whale. ICES J Mar Sci 76(1): 298-311.
  • VISSER IN, SMITH TG, BULLOCK ID, GREEN GD, CARLSSON OG & IMBERTI S. 2008. Antarctic peninsula killer whales (Orcinus orca) hunt seals and a penguin on floating ice. Mar Mammal Sci 24: 225-234.

Publication Dates

  • Publication in this collection
    29 July 2024
  • Date of issue
    2024

History

  • Received
    4 July 2023
  • Accepted
    23 Nov 2023
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