Great white shark hunters have expanded their "territory" in the ocean: where did these killers strike this time?

In 2023, the remains of a great white shark were washed ashore near Portland in Victoria, Australia. This incident captured the attention of both the media and scientists: one of the ocean's most formidable predators had been torn apart by something else that managed to remove its liver, as reported by IFLScience.

Researchers immediately suspected they knew the culprit, but could not confirm it until now: DNA analysis taken from the bite wound has confirmed the researchers' suspicions that orcas are hunting great white sharks in Australia.

In recent years, scientists have documented several instances of orca attacks on various species of sharks, and observations indicate that great white sharks have also been on their menu. For instance, a pair of orcas were known to have conducted a concerted shark hunt in 2022 and 2023. This behavior has made the pair of orcas famous, and rare instances of predation have been captured on camera, showing that orcas work together to attack their prey.

When the remains of the great white shark were found on the beach near Portland in 2023, it provided researchers with a unique opportunity to analyze individual bite wounds and identify the killer.

According to lead author of the study, PhD candidate from the Southern Shark Ecology Group at Flinders University and the Cetacean Research Centre of Western Australia, Isabella Reeves, upon examining the shark's body, they discovered that the liver, digestive, and reproductive organs of the predator were missing. The scientists also noted four characteristic bite marks: one was indicative of a liver extraction by an orca—similar behavior has been observed in South Africa.

The team took swabs from the bite wounds and then sequenced the residual genetic material of the predator. As a result, they were able to confirm the presence of orca DNA in the primary bite area, while DNA from the scavenger broadnose sevengill shark was found in three other wounds.

The researchers' findings compellingly indicate that orcas are indeed hunting white sharks in Australian waters. Moreover, scientists believe that these predators are particularly interested in the liver. According to Reeves, new data suggest that instances of predation may actually be more widespread globally than previously thought.

In their research, Reeves and colleagues employed wildlife forensic methods, which helped confirm the species responsible for the extraction and consumption of the sharks' livers. Two days before the shark's body was found on the beach, civilian witnesses reported seeing several orcas, including some well-known local individuals, hunting something large in the bay.

It is worth noting that this is not the first case of orca attacks on sharks in Australia. Previously, scientists had already documented that these predators were hunting blue sharks, mackerel sharks, shortfin mako sharks, bottom-dwelling sharks, and tiger sharks. However, the targeted consumption of the liver of a white shark had not been recorded in these waters, despite being observed elsewhere.

Back in 2015, orcas were seen interacting with a white shark in the marine park of the Neptune Islands group in South Australia. At that time, researchers noted a spot indicating a successful hunt, but the remains of the shark were never found.

In other regions, such as South Africa and California, attempts at orca predation on white sharks have led to disruptions in local shark populations. According to the study's author and marine biologist from Rhodes University, Dr. Alison Towner, direct observations of orca predation remain rare, and their frequency is actually poorly understood.

At the same time, studies have already shown that active orca predation on great white sharks in South Africa has led to significant cascading changes in the ecosystem. White sharks are key regulators in marine ecosystems, influencing their structure and functioning, and it remains unknown how hunting them will impact biodiversity in Australian waters.