Further insights into killer whales Orcinus orca preying on white sharks Carcharodon carcharias in South Africa

Full text

Full Terms & Conditions of access and use can be found at
https://www.tandfonline.com/action/journalInformation?journalCode=tams20
African Journal of Marine Science
ISSN: (Print) (Online) Journal homepage: www.tandfonline.com/journals/tams20
Further insights into killer whales Orcinus orca
preying on white sharks Carcharodon carcharias in
South Africa
A Towner, P Micarelli, D Hurwitz, MJ Smale, AJ Booth, C Stopforth, E Jacobs,
FR Reinero, V Ricci, A Di Bari, S Gavazzi, G Carugno, M Mahrer & E Gennari
To cite this article: A Towner, P Micarelli, D Hurwitz, MJ Smale, AJ Booth, C Stopforth, E Jacobs,
FR Reinero, V Ricci, A Di Bari, S Gavazzi, G Carugno, M Mahrer & E Gennari (01 Mar 2024):
Further insights into killer whales Orcinus orca preying on white sharks Carcharodon carcharias
in South Africa, African Journal of Marine Science, DOI: 10.2989/1814232X.2024.2311272
To link to this article: https://doi.org/10.2989/1814232X.2024.2311272
Published online: 01 Mar 2024.
Submit your article to this journal
View related articles
View Crossmark data

African Journal of Marine Science 2024, 46(1): 1–5
Printed in South Africa — All rights reserved
Copyright © NISC (Pty) Ltd
AFRICAN JOURNAL OF
MARINE SCIENCE
ISSN 1814-232X EISSN 1814-2338
https://doi.org/10.2989/1814232X.2024.2311272
African Journal of Marine Science is co-published by NISC (Pty) Ltd and Informa UK Limited (trading as Taylor & Francis Group)
This is the nal version of the article that is published
ahead of the print and online issue
Rapid communication
Further insights into killer whales Orcinus orca preying on white sharks
Carcharodon carcharias in South Africa
A Towner1,2* , P Micarelli3,4 , D Hurwitz5, MJ Smale6, AJ Booth1, C Stopforth7, E Jacobs8, FR Reinero4,
V Ricci4, A Di Bari4, S Gavazzi4, G Carugno4, M Mahrer9 and E Gennari1,10,11
1 Department of Ichthyology and Fisheries Science, Rhodes University, Makhanda, South Africa
2 South African International Maritime Institute (SAIMI), Ocean Sciences Campus, Nelson Mandela University, Gqeberha, South Africa
3 Department of Physical Sciences, Earth and Environment, University of Siena, Siena, Italy
4 Sharks Studies Centre – Scientific Institute, Massa Marittima, Italy
5 Simon’s Town Boat Company, Cape Town, South Africa
6 Department of Zoology and the Institute for Coastal and Marine Research, Nelson Mandela University, Gqeberha, South Africa
7 Drone Fanatics SA, Mossel Bay, South Africa
8 Keep Fin Alive, Mossel Bay, South Africa
9 W.M. Keck Science Department, Claremont McKenna College, Claremont, California, United States
10 Oceans Research Institute, Mossel Bay, South Africa
11 South African Institute for Aquatic Biodiversity (SAIAB), Makhanda, South Africa
* Corresponding author, e-mail: alisontowner@gmail.com
Photography and video footage, captured by researchers and tourists on board two vessels, provided insights into
the predation techniques employed by an adult male killer whale Orcinus orca in Mossel Bay, South Africa. The
incapacitation of its prey, a juvenile white shark Carcharodon carcharias (~2.5 m TL), followed by consumption
of the liver, occurred within less than 2 minutes, highlighting the predator proficiency of the killer whale. Notably,
another adult male killer whale, and constant traveling companion with the first, was observed approximately 100 m
away and was not involved during the predation. The following day a second carcass of a different eviscerated
white shark (3.55 m TL) washed ashore in the vicinity, indicating that at least two white sharks may have been killed
during the interaction.
Keywords: direct observation, foraging strategy, Mossel Bay, predation behaviour, white sharks
Elasmobranchs are possibly underestimated as prey
species in the diet of killer whales Orcinus orca (Fertl
et al. 1996); though documented records exist worldwide
(Reyes and García-Borboroglu 2004; Williams et al. 2009;
Jorgensen et al. 2019), these are often from remote
offshore locations. At least two populations of killer whales
have been identified as elasmobranch specialists—
in New Zealand waters (Visser 1999) and in the
northeastern Pacific (Ford et al. 2011). The risk of killer
whale predation prompts behavioural and distribution
changes in numerous marine predators (Pitman and
Durban 2010; Breed et al. 2017), where the ‘fight or flight’
response hinges on the trade-off between mortality risk
and access to prey (Ripple et al. 2014). Certain killer
whale populations specialise in a narrow prey range and
may display morphological and genetic distinctiveness
(Ford and Ellis 2014; Kiszka et al. 2021). In South Africa,
an offshore morphotype of killer whale was described
by Best et al. (2014), the first description of its kind in the
Southern Hemisphere. A distinctive pair of males, believed
to belong to this morphotype, appeared in the region in the
following year; they often hunted together and preyed on
various shark species, including white sharks Carcharodon
carcharias (Towner et al. 2022). The killer whales,
nicknamed Port and Starboard because of their dorsal fins
being bent in opposite directions, exhibited a predilection
for extracting and consuming the lipid-rich liver of sharks
(Engelbrecht et al. 2019; Towner et al. 2022), leading to
the displacement of various shark species from coastal
sites, including the broadnose sevengill shark Notorynchus
cepedianus, bronze whaler Carcharhinus brachyurus
and white shark Carcharodon carcharias, inducing
mesopredator release and trophic changes (Engelbrecht
et al. 2019; Hammerschlag et al. 2019; Towner et al. 2022).
While aerial footage has provided insights into the hunting
strategies employed by the killer whales in the region
(Towner et al. 2023), knowledge gaps persist regarding the
duration of a complete predation event and the potential
Introduction
Published online 01 Mar 2024

Towner, Micarelli, Hurwitz, Smale, Booth, Stopforth, Jacobs, Reinero, Ricci, Bari, Gavazzi, Carugno, Mahrer and Gennari
2
for solitary hunting of white sharks by these particular killer
whales, as opposed to cooperative foraging behaviour.
Materials and methods
Mossel Bay (34.1747° S, 22.0834° E) is located ~400 km
east of Cape Town in South Africa’s Western Cape Province
(Figure 1). Seal Island, situated ~800 m offshore (Jewell
et al. 2013; Gennari et al. 2022), was the focal point of
observations. Members of the public, either on land at the
village of Tergniet or aboard one of two vessels (named
Wildcatt and Shark Warrior), documented a killer whale pair
engaging in predatory behaviour against at least one white
shark in the Mossel Bay region. These sightings occurred
between 13:00 and 15:30, ~100 m south of Seal Island.
Results
At 12:30 on 18 June 2023, shore-based observations of
the killer whales Port and Starboard (herein referred to
as KWP and KWS) were reported at Tergniet. At 14:12,
in response to the sighting, an 8-m semi-rigid inflatable
vessel named Wildcatt launched from Mossel Bay harbour
and first sighted both killer whales south of Seal Island at
14:17. A notable surface slick was apparent, with diving
kelp gulls Larus dominicanus and the distinct smell of
shark liver (EJ and CS, pers. obs.) suggesting that a
predation event had occurred prior to the boat’s arrival.
The boat followed the killer whale pair—which remained
at least 100 m apart—for several minutes (Figure 2a,b).
KWP moved north of Seal Island and the vessel followed
him, before heading back to the south of Seal Island where
KWS remained >100 m away from KWP, on the other side
of the island (Figure 2a). At 15:02, a juvenile white shark
of ~2.5 m TL appeared at the surface, and KWS appeared
directly after it (Figure 2b,c). KWS then gripped the left
pectoral fin of the shark and thrust forward with the shark
several times before eventually eviscerating it (Figure 2). A
second vessel, named Shark Warrior, an 11.5-m catamaran
previously engaged in shark cage-diving activities at Seal
Island, remained ~100 m away and recorded video footage
of the events. Several minutes post-predation, researchers
on board Shark Warrior captured images of KWS with a
bloody piece of peach-coloured liver in its mouth (Figure 2i).
Discussion
Whereas solitary foraging behaviour has been observed
among specific killer whales in the sea around Cape
Town, exemplified by the activities of an individual killer
whale named Ettie (S Elwen and colleagues, Sea Search
Research & Conservation and Stellenbosch University,
AFRICA
South
Africa
SOUTH
AFRICA
Western
Cape
Cape
Town Mossel Bay

Mossel Bay
Tergniet Plettenberg Bay
Seal Island
INDIAN OCEAN

INDIAN OCEAN
Predation Seal Island Mossel Bay
Harbour
22°15 E
34°12 S
34° S
22°45 E 23°45 E23°15 E
Figure 1: Location of recent observations of the killer whale pair in Mossel Bay, Western Cape Province, South Africa

African Journal of Marine Science 2024, 46(1): 1–5 3
unpublished data), this research offers evidence that at
least one killer whale, known for shark predation, has the
ability to prey on subadult white sharks independently. All
other documented predation by killer whales on sharks
in the region has involved 2–6 individuals. Remarkably,
the period from seizing the shark by the pectoral fin to
eviscerating it lasted less than 2 minutes. Aerial footage
filmed in the same area the previous year had recorded
multiple predation events, including killer whales pursuing
and approaching white sharks. Initially, the white sharks
seemed unaware of the presence of killer whales but then
would begin tightly circling the killer whale in response to
being approached, with another killer whale blocking off
the shark’s offshore escape path (Towner et al. 2023).
These predation events persisted for nearly 2 hours and
involved about six killer whales, including KWS, in the
hunting activity. However, predation on a white shark by
a lone killer whale has not been documented previously.
An incident in False Bay where KWP was seen carrying
a bronze whaler shark in its mouth on 31 May 2019
(Towner et al. 2022) further supports the notion that lone
killer whales likely handle and immobilise juvenile and
subadult sharks (sized ~2.5–3.5 m TL). A white shark of
2.5 m TL would be expected to weigh ~100 kg and could
have a hepatosomatic index of between 5% and 24%
(i.e. a liver mass of 5–24 kg) (Cliff et al. 1989). However,
cooperative hunting might be required for killing larger
prey owing to the substantial size of large white sharks,
which can reach 6.5 m TL and 2.5 tonnes (Christiansen
et al. 2014).
This rapid communication builds on previous research
that these killer whales predominantly target the livers of
white sharks while discarding the rest of the carcass. On
19 June 2023, the day after the observed predation event
in this study, a fresh, subadult white shark carcass (3.55 m
TL) with its liver removed washed ashore at Mossel Bay,
~1 km from the site of the witnessed predation event
(Figure 3). Although direct observations of the predation
event were lacking, reports from observers on the vessel
Wildcatt indicated an oily slick, seabirds feeding on
the ocean surface, and the distinct smell of shark liver,
suggesting the possibility of another predation before their
arrival in the same area. Stretch marks along the shark’s
flanks may further align with observations of solitary
hunting for white sharks by KWS (Figure 2); however, it
remains unknown how killer whales open large sharks to
feed on their livers. The stretch marks, possibly indicating
either torsion or tension applied to the shark, might provide
a clue, but closer inspection of carcasses or more field
observations will be necessary to confirm the technique
used. Various carnivores selectively consume specific
anatomical portions of prey—examples include harbour
seals Phoca vitulina (Hauser et al. 2008), brown bears
Ursus arctos (Erlenbach et al. 2014), wolves Canis lupus
(a) (b)
(c)
(d)
(e)
(f) (g)
(h) (i)
Figure 2: Behavioural sequence of killer whales Orcinus orca around Seal Island in Mossel Bay, South Africa. (a) Killer whale ‘Port’ (KWP)
patrolling south, and then moving north of Seal Island and remaining >100 m from the predation event, with no further interaction with killer
whale ‘Starboard’ (KWS). (b) KWS surfaces near a juvenile white shark Carcharodon carcharias (~2.5 m TL) and then (c) seizes the shark’s
left pectoral fin, (d) causing the shark to bow and twist at the surface. (e) After a breath, KWS grasps the partially immobilised shark’s left
pectoral fin, pushing the shark forward again; submersion of the shark marks it for potential evisceration. (f, i) Kelp gulls Larus dominicanus
diving to feed on scraps of shark liver tissue, and a large oily surface slick appears. (g, h) KWS photographed post-event, holding a piece of
the shark’s peach-coloured liver in its mouth with some blood visible, at ~100 m north of the initial site. Photographs  Christiaan Stopforth
and Francesca Romana Romeiro/Sharks Studies Centre – Scientific Institute (SSCSI)

Towner, Micarelli, Hurwitz, Smale, Booth, Stopforth, Jacobs, Reinero, Ricci, Bari, Gavazzi, Carugno, Mahrer and Gennari
4
(Bosch et al. 2015) and indeed killer whales (Whitehead
and Reeves 2005).
Killer whales offer insights into ecological specialisation
and divergence within adaptable mammalian predators
(Ford and Ellis 2014). Research across global regions has
shown that the species can exhibit remarkably specialised
diets, selectively foraging for a small subset of potential
prey species in different regions. The rapid and swift
consumption of white shark prey by KWS in this study likely
reflects the adult predator’s skill and efficiency as opposed
to heightened vigilance against loss of prey to another
predator (Ford and Ellis 2014). Prey handling-time could
be influenced by anthropogenic stressors, especially while
spending periods hunting very close to the shoreline of a
major town (Engelbrecht et al. 2019; Towner et al. 2022).
In conservation strategies for vertebrate predators, an
understanding of both the hunting dynamics and nutritional
ecology is crucial (Kohl et al. 2015). Managing complex
interactions among protected species, particularly those
that have recently experienced population declines, poses
significant management difficulties (Moxley et al. 2019).
Such challenges could become even more pronounced as a
result of ecosystem alterations triggered by climate change
and other human-induced stresses (Carnicer et al. 2011;
Moritz et al. 2012). These evolving conditions underscore
the significance of adaptable conservation strategies and
vigilant ecological monitoring.
Acknowledgements — Thanks are extended to Elton Polly of
Go Dive and the staff of White Shark Africa, whose vessels provided
the platforms for these observations. We thank the Department of
Forestry, Fisheries and the Environment for permitting the ongoing
research on this topic. Thanks also to Dr Simon Elwen and
various members of the Killer Whale Sightings Group where these
observations were reported.
ORCID
Anthony John Booth: https://orcid.org/0000-0002-5561-9260
Enrico Gennari: https://orcid.org/0000-0002-4334-727X
Esther Jacobs: https://orcid.org/0000-0001-7769-9567
Primo Micarelli: https://orcid.org/0000-0003-0582-3770
Francesca Ramana Reinero: https://orcid.org/0000-0001-8400-1227
Malcolm Smale: https://orcid.org/0000-0002-1135-8687
Alison Towner: https://orcid.org/0000-0002-9420-7066
References
Best PB, Meÿer MA, Thornton M, Kotze PGH, Seakamela SM,
Hofmeyr GJG et al. 2014. Confirmation of the occurrence of a
second killer whale morphotype in South African waters. African
Journal of Marine Science 36: 215–224.
Bosch G, Hagen-Plantinga EA, Hendriks WH. 2015. Dietary
nutrient profiles of wild wolves: insights for optimal dog nutrition.
British Journal of Nutrition 113 (Suppl. 1): S40‒S54.
Breed GA, Matthews CJD, Marcoux M, Higdon JW, LeBlanc B,
Petersen SD, Ferguson SH. 2017. Sustained disruption of narwhal
habitat use and behavior in the presence of Arctic killer whales.
Proceedings of the National Academy of Sciences of the United
States of America 114: 2628–2633.
Carnicer J, Coll M, Ninyerola M, Pons X, Sanchez G, Penuelas J.
2011. Widespread crown condition decline, food web disruption,
and amplified tree mortality with increased climate change-type
drought. Proceedings of the National Academy of Sciences of
the United States of America 108: 1474–1478.
Christiansen HM, Lin V, Tanaka S, Velikanov A, Mollet HF,
Wintner SP et al. 2014. The last frontier: catch records of white
sharks (Carcharodon carcharias) in the northwest Pacific Ocean.
PLoS ONE 9: e94407.
Cliff G, Dudley SFJ, Davis B. 1989. Sharks caught in the protective
gill nets off Natal, South Africa. 2. The great white shark
Carcharodon carcharias (Linnaeus). South African Journal of
Marine Science 8: 131–144.
(a) (b)
Figure 3: (a) On 19 June 2023 (the morning after the documented predation event), a dead white shark Carcharodon carcharias, this time
a different subadult measuring 3.55 m TL, washed ashore ~1 km from the previous predation site in Mossel Bay. A necropsy revealed
that, similar to other sharks preyed on by killer whales in the region, the white shark had been torn open at the pectoral girdle and its liver
removed. (b) The white shark’s carcass showed prominent stretch marks along the flanks, possibly induced by the strategy observed
with KWS and described in Figure 2; however, this is speculative as predation on this shark was not observed and it could have been
cooperatively hunted by both KWS and KWP. Photographs  Christiaan Stopforth

African Journal of Marine Science 2024, 46(1): 1–5 5
Engelbrecht TM, Kock AA, O’Riain MJ. 2019. Running scared:
when predators become prey. Ecosphere 10: e02531.
Erlenbach JA, Rode KD, Raubenheimer D, Robbins CT. 2014.
Macronutrient optimization and energy maximization determine
diets of brown bears. Journal of Mammalogy 95: 160–168.
Fertl DA, Acevedo-Gutierrez A, Darby FL. 1996. A report of killer
whales feeding on a carcharhinid shark in Costa Rica. Marine
Mammal Science 12: 606–611.
Ford JK, Ellis GM. 2014. You are what you eat: foraging
specializations and their influence on the social organization and
behavior of killer whales. In: Yamagiwa J, Leszek Karczmarski L
(eds), Primates and cetaceans: field research and conservation
of complex mammalian societies. Tokyo: Springer. pp 75–98.
Ford JK, Ellis GM, Matkin CO, Wetklo MH, Barrett-Lennard LG,
Withler RE. 2011. Shark predation and tooth wear in a population
of northeastern Pacific killer whales. Aquatic Biology 11:
213–224.
Gennari E, Irion DT, Cowley PD. 2022. Active acoustic telemetry
reveals ontogenetic habitat-related variations in the coastal
movement ecology of the white shark. Animal Biotelemetry 10:
article 25.
Hammerschlag N, Williams L, Fallows M, Fallows C. 2019.
Disappearance of white sharks leads to the novel emergence
of an allopatric apex predator, the sevengill shark. Scientific
Reports 9: article 1908.
Hauser DD, Allen CS, Rich Jr HB, Quinn TP. 2008. Resident
harbour seals (Phoca vitulina) in Iliamna Lake, Alaska:
summer diet and partial consumption of adult sockeye salmon
(Oncorhynchus nerka). Aquatic Mammals 34: 303–309.
Jewell OJD, Johnson RL, Gennari E, Bester MN. 2013. Fine-scale
movements and activity areas of white sharks (Carcharodon
carcharias) in Mossel Bay, South Africa. Environmental Biology
of Fishes 96: 881–894.
Jorgensen SJ, Anderson S, Ferretti F, Tietz JR, Chapple T, Kanive P
et al. 2019. Killer whales redistribute white shark foraging
pressure on seals. Scientific Reports 9: article 6153.
Kiszka JJ, Caputo M, Méndez-Fernández P, Fielding R. 2021.
Feeding ecology of elusive Caribbean killer whales inferred from
Bayesian stable isotope mixing models and whalers’ ecological
knowledge. Frontiers in Marine Science 8: article 423.
Kohl KD, Coogan SC, Raubenheimer D. 2015. Do wild carnivores
forage for prey or for nutrients? Evidence for nutrient‐specific
foraging in vertebrate predators. BioEssays 37: 701–709.
Moritz MA, Parisien MA, Batllori E, Krawchuk MA, Van Dorn J,
Ganz DJ, Hayhoe K. 2012. Climate change and disruptions to
global fire activity. Ecosphere 3: 1–22.
Moxley JH, Nicholson TE, Van Houtan KS, Jorgensen SJ. 2019.
Non‐trophic impacts from white sharks complicate population
recovery for sea otters. Ecology and Evolution 9: 6378–6388.
Pitman RL, Durban JW. 2010. Killer whale predation on penguins in
Antarctica. Polar Biology 33: 1589–1594.
Reyes LM, García-Borboroglu P. 2004. Killer whale (Orcinus
orca) predation on sharks in Patagonia, Argentina: a first report.
Aquatic Mammals 30: 376–379.
Ripple WJ, Estes JA, Beschta RL, Wilmers CC, Ritchie EGH,
Hebblewhite M et al. 2014. Status and ecological effects of the
world’s largest carnivores. Science 343: 124–148.
Towner AV, Watson RGA, Kock AA, Papastamatiou Y, Sturup M,
Gennari E et al. 2022. Fear at the top: killer whale predation
drives white shark absence at South Africa’s largest aggregation
site. African Journal of Marine Science 44: 139–152.
Towner AV, Kock AA, Stopforth C, Hurwitz D, Elwen SH. 2023.
Direct observation of killer whales preying on white sharks and
evidence of a flight response. Ecology 104: e3875.
Visser I. 1999. Benthic foraging on stringrays by killer whales
Orcinus orca in New Zealand waters. Marine Mammal Science
15: 220‒227.
Whitehead H, Reeves R. 2005. Killer whales and whaling: the
scavenging hypothesis. Biology Letters 1: 415–418.
Williams AJ, Petersen SL, Goren M, Watkins BP. 2009. Sightings
of killer whales Orcinus orca from longline vessels in South
African waters, and consideration of the regional conservation
status. African Journal of Marine Science 31: 81–86.
Manuscript received September 2023 / revised December 2023 / accepted January 2024