Did orcas kill a great white shark near Cape Bridgewater?

Beachgoers found the carcass of a 4.7 metre great white shark that was covered in bite marks at Cape Bridgewater on October 17, 2023.

Deakin University Warrnambool's associate professor in marine science Adam Miller said it was important to establish what had caused the shark's death.

He said it was rare for orcas, which had been sighted in the area, to kill the 'vulnerable' species.

If researchers established that was the case, it could lead to major impacts on marine life in the region.

"It could very well have been an aged individual that had passed away and been subsequently fed upon by marine predators," he told The Standard.

"But the fact that there were observations of orcas potentially predating on a large prey item in Discovery Bay within a 24-hour period of that shark washing up, it certainly raised a few flags."

WARNING: GRAPHIC IMAGE

Mr Miller said he was unaware of any documented orca attacks on great whites in Australia although killer whales were their only natural predator.

"We've actually taken genetic samples from the bite marks on the carcass and we'll hope to determine what the predator was," he said.

The researcher was concerned what an orca attack could mean for the great white shark population, which has been categorised as 'vulnerable' by the International Union for Conservation of Nature (IUCN) since 1996.

Vital samples were taken from the carcass before it was stored in a deep freeze. Mr Miller said the specimen would prove 'absolutely invaluable' in ongoing research.

Research teams were unable to determine the specimen's gender due to its level of decay although its large size suggests it was more likely to be female.

IN OTHER LOCAL NEWS:

Before they were inevitably overshadowed by the shark, killer whales at Cape Nelson created an online buzz when they were spotted just after noon on October 15.

South-west photographer Allen McCauley was able to watch them for several hours as they hunted local prey.

"It looked like there was a lot of fish there, they (the orcas) just kept going round and round in circles," he said.

"We surmise that they were probably chasing salmon."

Mr McCauley said there were at least seven killer whales present, two of which were well-known males 'Bent Tip' and 'Ripple'.

The whales are easily distinguished by their dorsal fins, with one having a curved end and the other featuring a ripple-like pattern down the spine.

Fellow photographer Michelle Holcombe said it was amazing to catch sight of the orcas.

"This is only the second time I've seen them but they have been spotted quite a bit. You've just got to be lucky to be there," she said.

"Good timing really, that's all it is. You can sit out there for weeks and not see a thing."

A spokesperson for the Department of Energy, Environment and Climate Action (DEECA) said due to their high mobility and vast range, orca sightings weren't common in Victoria.

Sightings that do occur aren't dictated by season as movement patterns are largely driven by available food.

"There is still a lot to learn about the populations of orcas that are seen in Victorian waters but we do know they can range from the coast of New South Wales to Tasmania to as far west as Portland," they said.

Despite their name and reputation as savage predators, killer whales rarely attack humans. Only four fatal bites have ever been documented, all of which occurred in captivity.

Our journalists work hard to provide local, up-to-date news to the community. This is how you can access our trusted content: