For the first time, DNA evidence has confirmed that killer whales in Australia prey on white sharks specifically for their liver, a discovery that offers fresh insight into the behavior of these apex predators and their impact on marine ecosystems. The findings, detailed in a study published in the journal Ecology and Evolution, were based on DNA analysis of bite wounds found on the carcass of a large white shark that washed ashore near Portland, Victoria, in 2023.
The Unique Case of the White Shark Carcass
The shark in question, a 4.7-meter white shark (Carcharodon carcharias), was found missing its liver, digestive organs, and reproductive organs—a highly unusual and significant sign of predation. Four distinctive bite marks were found on the shark’s body, with one wound notably resembling those left by killer whales when they extract the liver. This behavior, though documented in places like California and South Africa, had never been confirmed in Australia until now.
The study, led by Isabella Reeves, a Ph.D. candidate with Flinders University’s Southern Shark Ecology Group and the West Australian Cetacean Research Center (CETREC), utilized wildlife forensic techniques to analyze DNA from the shark’s bite wounds. The analysis revealed that killer whale DNA was present in the primary bite area, providing compelling evidence that killer whales had indeed hunted the shark and selectively consumed its liver. The remaining three bite wounds were identified as originating from broadnose sevengill sharks, scavengers that had fed on the remains of the shark after the killer whales had taken their preferred organ.
Killer Whale Predation on Sharks: A Global Phenomenon
This groundbreaking study is the first to definitively confirm killer whale (Orcinus orca) predation on white sharks in Australian waters, highlighting the selective nature of their feeding habits. The liver, rich in fats and nutrients, is a highly desirable food source, and killer whales have been observed targeting this organ in other parts of the world. Previously, similar behaviors had been recorded in California and South Africa, where killer whales were known to hunt white sharks and remove their livers with remarkable precision.
The Bridgewater Bay incident, where bystanders witnessed several killer whales, including individuals known as “Bent Tip” and “Ripple”, hunting a large prey just days before the shark carcass washed ashore, suggests that this type of predation may be more widespread than previously understood. The killer whales’ preference for shark liver raises questions about the potential ecological impact such behavior may have on marine food chains, especially considering the important role of white sharks in regulating marine ecosystems.
Implications for Marine Ecosystems
The study’s authors stress the importance of understanding the broader implications of these interactions. Associate Professor Adam Miller, a senior ecologist with Cesar Australia and a senior author of the study, points out that killer whale predation on white sharks could lead to shifts in local marine ecosystems. In regions like South Africa, where similar interactions have been documented, white shark populations have been disrupted, leading to cascading effects on the ecosystem. Since white sharks are considered key regulators of marine ecosystems, their decline could have far-reaching consequences, affecting other species and the balance of marine life.
Dr. Alison Towner, a marine biologist from Rhodes University in South Africa and a co-author of the study, highlights how these killer whale predations have caused disturbances in local shark populations, with potential long-term consequences for the species involved. However, the frequency of these interactions remains poorly understood due to the rarity of direct observations.
While the Australian study doesn’t yet provide data on the frequency of killer whale predation on white sharks in the region, it underscores the need for ongoing monitoring of these interactions. Dr. Lauren Meyer, a research fellow at Flinders University and another author of the study, emphasizes that the selective consumption of shark liver by killer whales suggests that scavenging is an important component of their behavior, with their feeding habits contributing to the nutrient cycling within marine ecosystems.
The Broader Picture: A Changing Marine Food Web
The findings of this study also add to a growing body of evidence showing that killer whales are capable of altering marine food webs. The selective removal of specific organs from their prey—such as shark livers—helps maintain a balance within the ecosystem. By leaving much of the shark carcass behind for scavengers, killer whales facilitate the redistribution of nutrients throughout the ecosystem, benefiting a variety of marine species.
In recent years, scientists have increasingly observed killer whales exploiting different prey types and exhibiting a wide range of hunting strategies. Their interactions with white sharks, including the liver extraction, further demonstrate the adaptability and intelligence of these animals. In regions where such predation is more common, the killer whale’s role as a top predator is becoming more evident, and understanding their impact on marine food webs is critical for effective conservation efforts.
The Need for Further Research
Despite the groundbreaking nature of this study, much remains unknown about the frequency and full extent of killer whale predation on white sharks in Australia. The interactions between killer whales and white sharks are still not well understood, and additional research is needed to determine how these events may be affecting the populations of white sharks and other shark species in the region.
For now, the study serves as a reminder of the complexities of marine ecosystems and the interconnections between species. As apex predators, killer whales play a crucial role in shaping these ecosystems, and their ability to hunt and selectively consume certain organs from their prey highlights the sophisticated nature of their hunting strategies.
In conclusion, this DNA-based confirmation of killer whale predation on white sharks in Australian waters not only opens up new avenues for understanding the ecological dynamics of marine life but also underscores the importance of preserving these top predators. With white sharks being key regulators of marine ecosystems, maintaining healthy populations is essential for the stability of oceanic food webs, making ongoing research and conservation efforts crucial for the long-term health of our oceans.
Reference: Isabella M. M. Reeves et al, Genetic Evidence of Killer Whale Predation on White Sharks in Australia, Ecology and Evolution (2025). DOI: 10.1002/ece3.70786