Species Distribution Modeling of Killer Whales (Orcinus orca) in Australian Waters

The killer whale (Orcinus orca) is a globally distributed apex predator. This species is represented by distinct ecotypes or forms, which are well documented in the Northern Hemisphere and Antarctica. However, less is known about killer whales in Australia. While research efforts have been made to study these animals, a broader understanding of their range and drivers of occurrence is lacking. In this study, we model the spatial distribution of killer whales in Australian waters to identify potential areas of habitat suitability and conservation priority. A total of 1310 sightings were compiled, of which 1115 were used alongside a suite of static and dynamic predictor variables to build presence-only MaxEnt species distribution models (SDMs) in three separate study areas: southeast (SE), southwest (SW) and northwest (NW) Australia. The SDMs identified potential areas of habitat suitability both within and outside of known locations for killer whales in Australia. All three models returned good discriminative power between presence and background points. However, good predictive power was only suggested for the SE and NW. The importance of certain predictor variables indicated a preference for different environmental conditions, supporting the notion of at least two ecologically distinct groups. Killer whales frequenting the SE and SW preferred temperate waters, whereas those in the NW preferred tropical waters. This work greatly increases our understanding of killer whales in Australian waters and identifies potential areas of biological importance for management and monitoring. It also complements ongoing research into their genetics, feeding ecology, and diversification, showcases the utility of citizen science data, and informs the conservation of this species, which is still considered data deficient and remains to be adequately protected under Australian Government legislation.