Marine Greek Tragedy

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The first direct evidence of orcas hunting and killing white sharks in South Africa has been captured by a helicopter and drone pilot in separate footage, and a new paper published on Monday in The Ecological Society of America’s journal Ecology analyzes the footage, which provides new evidence that orcas are capable of pursuing, capturing and incapacitating white sharks.

This has opened a new window of possible scientific study into aspects of white shark and orca behaviour, including distribution, flight response, hunting habits, and communication.

One predation event was filmed on a drone, but the researchers believe that three other sharks may also have been killed. While a clip of the drone footage was aired in June, this was only part of an hour-long hunt of multiple sharks, as revealed by the exclusive helicopter footage (the pilot used his cellphone).

The new paper offers more extensive footage, along with data from tags, drone surveys and shark-tour boats showing that white sharks fled from the Mossel Bay region of South Africa for several weeks.

LEANING TO THE RIGHT: Starboard is a weird old orca, what with the fin, and the livers.

Only two killer whales in South Africa - Port and Starboard - have been linked to hunting white sharks, but they’ve never been seen ‘in action’. Orcas have been observed preying on other shark species, but direct observation of predation on white sharks locally had never been seen.

“This behavior has never been witnessed in detail before, and certainly never from the air,” said lead author Alison Towner, a senior shark scientist at Marine Dynamics Academy in Gansbaai, South Africa.

Port and Starboard have rare and distinct collapsed dorsal fins. Port's fin collapses left and Starboard's collapses right.

Starboard was observed in the new footage as part of a pod of four other killer whales, which suggests that the trend to attack white sharks for their liver may be spreading in what scientists call cultural learning. Starboard could be seen eating what was suspected to be a large piece of shark liver at the ocean surface.

COMMUNITY MINDED: A pod of killer whales keeps a lookout for some yummy livers.

The study also gives new insights into sharks’ attempts to evade orcas. On two occasions, orcas approached sharks closely and slowly, while the shark, instead of fleeing, stays close to the orca to keep an eye on it. This is a common strategy that seals and turtles use to evade sharks, but it would be rendered useless against a predator that hunts as a pack.

In the footage, while the shark focuses on the orca in front of it, another orca blindside the shark right in the area of its liver. Survival strategy can’t be the forte of a solo animal who sees itself as an apex predator, whereas orca are dynamic and work as a collective.

“Killer whales are highly intelligent and social animals. Their group hunting methods make them incredibly effective predators,” said marine mammal specialist and study co-author Dr Simon Elwen, Director of Sea Search and a research associate at Stellenbosch University.

“I first saw Starboard in 2015 when he and his close-associated ‘Port’ were linked to killing sevengill sharks in False Bay. We saw them kill a bronze whaler [copper shark] in 2019 – but this new observation is really something else,” said David Hurwitz, a boat-based whale-watching operator from Simon’s Town Boat Company.

The new study also analyzed drone and cage dive boat survey data before and after these predation events. White sharks were seen on every survey day for the weeks prior to the predation event and multiple sharks were seen on the day of the predations. However, only a single white shark was seen in the 45 days after the predations, confirming a flight response by sharks.

“We first observed the flight responses of seven gills and white sharks to the presence of killer whales Port and Starboard in False Bay in 2015 and 2017. The sharks ultimately abandoned former key habitats, which has had significant knock-on effects for both the ecosystem and shark-related tourism,” said South African National Parks’ shark expert and marine biologist, Dr Alison Kock.

Previous studies have documented how new behaviors spread among killer whales over time through cultural transmission. The authors suggest that if more killer whales adopt the practice of hunting white sharks, then the behavior will have far wider impacts on shark populations.

About the Authors

Alison V. Towner PhD Candidate -- Department of Ichthyology and Fisheries Science, Rhodes University, South Africa & Dyer Island Conservation Trust, Kleinbaai , South Africa. www.instagram.com/alisontowner/

Alison A. Kock PhD -- South African National Parks, Cape Research Centre, Cape Town, South Africa & South African Institute for Aquatic Biodiversity (SAIAB), South Africa.
www.twitter.com/UrbanEdgeSharks

Christiaan Stopforth -- Drone Fanatics SA, Mossel Bay, South Africa. www.instagram.com/dronefanaticssa/

David Hurwitz --Simons Town Boat Company, Simon’s Town, South Africa www.boatcompany.co.za

Simon H. Elwen PhD -- Sea Search Research and Conservation NPC, Cape Town, South Africa & Department of Botany and Zoology, Faculty of Science, Stellenbosch University, South Africa.

www.seasearch.co.za www.instagram.com/seasearchresearch www.twitter.com/simonelwen