New behaviours adopted by killer whales through cultural transmission

The first direct evidence of orcas, or killer whales, killing white sharks in South Africa has been captured by both a helicopter and drone pilot.

A new paper published yesterday in the Ecological Society of America’s journal, Ecology, presents both sets of video footage, providing new evidence that orcas are capable of pursuing, capturing and incapacitating white sharks.

One predation event was filmed on a drone, but researchers believe that three other sharks may also have been killed.

While a clip of the drone footage was aired in June, it was only part of an hour-long hunt of multiple sharks, as revealed by the helicopter footage, and the new paper has more extensive footage, along with data from tags, drone surveys and shark-tour boats showing white sharks fled from the Mossel Bay region for weeks.

Orcas have been observed preying on other shark species, but direct observation of predation on white sharks locally has been lacking until now, said lead author Alison Towner, senior shark scientist at Marine Dynamics Academy in Gansbaai.

Only two killer whales in South Africa have been previously linked to hunting white sharks, but never seen “in action”.

Only one of those animals was seen in the new footage, along with four other orcas. The authors believe this suggests the behavior may be spreading.

The study also gives new insights into sharks’ attempts to evade capture by orcas. On two occasions, orcas approached sharks closely and slowly, while the shark, instead of fleeing, stayed close to the orca, keeping it in view– a common strategy seals and turtles use to evade sharks.

But orcas hunt in groups and researchers believe these behaviors may render the circling strategy ineffective for white sharks.

“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.

The study confirmed that one infamous killer whale, locally known as Starboard, was part of the pod and ate what was suspected to be a large piece of shark liver at the ocean surface.

The novel footage also revealed how another killer whale bit into a white shark in the region of the liver. “I first saw Starboard in 2015 when he and his close-associate Port were linked to killing seven gill 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 whale-watching operator from Simon’s Town Boat Company.

The new study also analysed drone and cage dive boat survey data before and after these predation events.

White sharks were seen on every survey day for weeks prior to the predation event and multiple sharks were seen on the day of the predations, but 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 the ecosystem and shark-related tourism,” said SA National Parks’ shark expert, Dr Alison Kock.

Studies have documented how new behaviours spread among killer whales through cultural transmission. The authors suggest if more killer whales adopt the practice of hunting white sharks, the behaviour will have far wider impacts on shark populations.

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– news@citizen.co.za