It was theorised that orca whales hunted great white sharks but now there is video proof. Photo: Unsplash / Tim Cole
By Velvet Winter
Scientists have captured the first direct evidence of orca whales hunting and killing great white sharks, with new drone and aerial footage demonstrating what had previously only been formally described by just three studies.
Orcas have been observed preying on other shark species, but direct observation of predation on great white sharks had been lacking - until now.
A new study published in the journal Ecology this week detailed killer orca attacks on great white sharks off the coast of South Africa in May.
Scientists published video condensing an hour-long hunt by multiple orcas into a three-minute clip on YouTube.
"This behaviour has never been witnessed in detail before, and certainly never from the air," lead author Alison Towner, a senior shark scientist at Marine Dynamics Academy in Gansbaai, South Africa, said.
Two killer whales in South Africa had previously been linked to hunting great white sharks, but the predation had never been seen "in action".
One of those animals was observed in the new footage, along with four other killer whales. The authors believe the involvement of these four new whales suggests the behaviour 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 that seals and turtles use to evade sharks.
But researchers believe the circling strategy is ineffective against orcas for great white sharks.
"Killer whales are highly intelligent and social animals," study co-author Simon Elwen said.
"Their group hunting methods make them incredibly effective predators."
Killer whales live up to their name
While the drone footage marks the first video evidence of orcas consuming a great white shark, scientists have previously observed the half-eaten carcasses of great whites that have been left by orcas.
Between February and June 2017, five great white shark carcasses washed up on beaches in Gansbaai, Western Cape Province, four of which had had their livers removed.
Shark livers are high in nutrient-rich lipids, with researchers observing that selective feeding on energy-rich prey is a hunting strategy frequently used by killer whales.
However, sharks are not the only prey that orcas target.
They have been observed ganging up to hunt sea lions and seals, often slapping their prey metres into the air with their tails to incapacitate them.
Orcas have also been observed surging onto beaches to snag prey before wriggling back into the water with their catch.
Due to their apex predator behaviour, humans have also become targets when orcas have been kept in captivity.
The most recent fatal attack by an orca in captivity was in 2010 when SeaWorld trainer Dawn Brancheau was killed by an adult male orca named Tilikum in front of an audience in Orlando, Florida.
The trainer's death inspired the explosive 2013 documentary Blackfish, which followed Tilikum who had killed two other people prior to the attack on Brancheau.
The film advocated against holding orcas captive, arguing the stress of being imprisoned made the animals hostile towards humans and other orcas.
By March 2016, SeaWorld had stopped presenting live orca shows and discontinued its orca breeding programme.
Tilikum died from a bacterial infection while in captivity in 2017.
- ABC
