Unveiling Orca Diets in the Bremer Sub-Basin
We are excited to announce that in the upcoming season, Naturaliste Charters will be collaborating with researchers from Oceans Blueprint to investigate the feeding ecology and orca diet of the population that gathers seasonally in the Bremer Sub-Basin, Western Australia.
The Bremer orcas are believed to be generalist feeders, known to prey on fish, squid, sharks and toothed whales. They are known to even predate baleen whales such as humpbacks, Antarctic minke whales, and blue whales. Yet, despite years of observations, questions remain around the orca diet of this population. Gaining a clearer understanding of what these apex predators eat is vital to inform species conservation and ecosystem management.
A Unique Opportunity for Research
Naturaliste Charters provides a unique research platform, with our vessel Alison Maree visiting the Bremer Sub-Basin daily from December through April. During our tours, we sometimes witness predation events where orcas take down large, often unidentifiable prey. Usually, only fleeting glimpses are visible at the surface — oil slicks, tissue remnants, or dramatic behavioural displays — leaving many unanswered questions about the prey involved and the composition of the orca diet.
The Bremer Sub-Basin Sampling Project
In the 2025/26 season, we will launch the Bremer Sub-Basin Sampling Project. Our marine biologists will work alongside Oceans Blueprint researchers on our daily charters to collect tissue remains and water samples for environmental DNA (eDNA) analysis. This innovative approach will help identify prey species and provide new insights into the orca diet of the Bremer population, filling critical gaps in knowledge.
By combining Naturaliste Charters’ extensive local experience with Oceans Blueprint’s expertise in marine mammal ecology and genetics, the project aims to shed light on predator-prey dynamics in this offshore ecosystem. The findings will not only deepen our understanding of orca feeding behaviour but also provide valuable data on prey species, many of which are currently listed as ‘Data Deficient’ by the IUCN.
Conservation Through Collaboration
This collaboration demonstrates the important role eco-tourism can play in advancing marine science. By leveraging daily whale watching expeditions as research opportunities, we can contribute to meaningful conservation outcomes while continuing to provide unforgettable wildlife experiences for our passengers.
We are proud to support research that highlights the ecological importance of the Bremer Sub-Basin and the incredible orcas that call it home each summer.
This research will be conducted under Animal Ethics Approval and with Marine Park, Commonwealth, and Cetacean Research Approvals.
REFERENCES
Salgado Kent, C., Bouchet, P., Wellard, R., Parnum, I., Fouda, L., & Erbe, C. (2020). Seasonal productivity drives aggregations of killer whales and other cetaceans over submarine canyons of the Bremer Sub-Basin, south-western Australia. Australian Mammalogy, 43, 168–178. 10.1071/AM19058
Totterdell, J., Wellard, R., Reeves, I., Elsdon, B., Markovic, P., Yoshida, M., Fairchild, A., Sharp, G., Pitman, R. (2022). The first three records of killer whales (Orcinus orca) killing and eating blue whales (Balaenoptera musculus). Marine Mammal Science, 38, 1-16. 10.1111/mms.12906.
Wellard, R., Lightbody, K., Fouda, L., Blewitt, M., Riggs, D., & Erbe, C. (2016). Killer whale (Orcinus orca) predation on beaked whales (Mesoplodon spp.) in the Bremer Sub-Basin, Western Australia. PloS ONE, 11(12), e0166670. 10.1371/journal.pone.0166670
Wellard, R. (2018). Vocal repertoire, social structure and feeding preferences of Australian and Antarctic killer whales (Orcinus orca). Curtin University.
