Great white near Portland becomes Australia's first confirmed orca kill

The 4.7 metre predator was found covered in bite marks at Cape Bridgewater on October 17, 2023.

This came just days after a pod of killer whales was spotted in the region, the great white's only natural predator.

A month on, further research into the shark's wounds has shed light on its death.

Deakin University Warrnambool's associate professor in marine science Adam Miller said the size and location of the bites were characteristic of killer whale predation.

"We were able to confirm through genetic analysis that those bite wounds were just loaded with orca DNA," he told The Standard.

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While scavenger species such as sevengill sharks had fed on its body, a bite more than 50cm wide was attributed to a killer whale attack.

Great whites are more often competitors to the whales rather than prey but orcas are known to target the fish's liver for its high nutritional value.

Despite this, Mr Miller said there had only been about nine reports of the two species interacting in Australia and New Zealand with just a few of those instances involving killer whales harassing the smaller predator.

"This is the first direct evidence of a white shark being killed by orcas in Australian waters," he said.

Due to how isolated from human contact both species can be, it's unknown how frequent these attacks are.

"The only hard evidence we have is coming from South Africa where there are a pair of killer whales called Port and Starboard," Mr Miller said.

"They've shifted their behaviour over the last decade to really start targeting white sharks in the south-east of the country.

"It's had a measurable impact on their numbers in South Africa both through direct killing and displacement.

"For a species that has been hunted to a point where it was critically endangered, it's a worry when you start losing a lot of large, mature adults."

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But the marine biologist said this incident wasn't a conservation concern until it became a series of attacks.

"We just need to monitor and keep an eye on it. It could be an isolated event or happen frequently offshore," he said.

The shark is now in the hands of the Melbourne Museum, where it may be put on display.

Mr Miller said it was a good outcome for the carcass, which was beginning to decay and lose its value for research purposes.