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While well-documented in the Northern Hemisphere and Antarctica, much less is known about killer whales (Orcinus orca) in Australia. However, orcas are actually sighted year-round in all coastal states and territories. A new Flinders University study has now mapped this across three key regions.

Research led by Flinders University's Cetacean Ecology, Behavior and Evolution Lab (CEBEL) models the distribution of killer whales in Australian waters, shedding light on habitat preferences and uncovering ecological distinctions between populations.

A collaboration with the Cetacean Research Center of WA, Project ORCA and Killer Whales Australia, the paper in Ecology and Evolution collates 1,310 sightings of killer whales around the country from the past four decades.

Species distribution modeling is used to pinpoint places of high habitat suitability in southeast, southwest, and northwest Australia—notably the Bonney Upwelling (South Australia / Victoria), Bremer Sub-basin (Western Australia), and Ningaloo Reef (WA).

"This work greatly increases our understanding of killer whales in Australian waters and identifies areas of biological importance for management and monitoring," says Flinders University CEBEL Ph.D. candidate Marissa Hutchings, lead author of the article.

"Not only now do we have a nationwide picture, but our findings also support the idea that at least two ecologically distinct forms of killer whales exist in Australia—a temperate and a tropical form."

The research calls for stronger conservation measures to protect these unique populations—"particularly given their role as apex predators in the marine ecosystem and the fact that some of their most important habitats are currently only partially protected by legislation," she says.

"More research will be vital in ensuring that this species can be adequately managed in a changing environment, but this will only be made possible by collaboration between researchers, citizen scientists, and marine users to improve the size and accessibility of datasets on both killer whales and their prey."

Another author on the paper, Flinders University Associate Professor Guido Parra, says differences in range and drivers of occurrence are important to recognize because anthropogenic stressors such as commercial fishing, marine tourism, offshore drilling, and chemical pollutants are becoming increasingly prevalent in Australia.

Senior author Flinders Associate Professor Luciana Möller says the study complements ongoing research into the genetics, feeding ecology and diversification of Australia's killer whale populations—as well as highlights the usefulness of citizen science data.

"We hope this study will help inform the conservation of this species, which is still considered data deficient and remains to be adequately protected under Australian Government legislation."