Killer whales are known to enjoy a varied diet but new research from Curtin University has found their menu is more extensive than previously thought, showing them to interact with, hunt and prey upon beaked whales.
Curtin University Centre for Marine Science and Technology PhD candidate Rebecca Wellard said observations of killer whales (Orcinus orca) feeding on the remains of beaked whales had previously been documented.
However, to date, there had been no published account of killer whales actively preying upon beaked whales (Mesoplodon spp.).
“Prey specialisations of killer whale communities in the Northern Hemisphere have been well documented over the last four decades and can be used to distinguish between sympatric non-interbreeding populations,” Ms Wellard said.
“However, very little is known about killer whales in Australian waters, their abundance, movements, behaviour, demographics, ecology or population status, and descriptions of their feeding behaviour and prey preferences is generally lacking.”
The whales were observed carrying out this behaviour on four separate occasions during 2014, 2015 and 2016 in the Bremer Sub-Basin, off the south coast of Western Australia.
“While encounters with killer whales are typically rare and unpredictable in Australian waters, the area offshore from Bremer Bay appears to support abundant killer whales during the austral summer, and provides an opportunity to study this little-known population,” Ms Wellard said.
The killer whale is found all over the world in shallow coastal waters to deep offshore waters. They are a dominant oceanic predator, feeding on a variety of vertebrate and invertebrate species, including other marine mammals, seabirds, fish, sharks, squid and turtles.
Despite killer whales being sighted in all Australian waters, most sighting data are incidentally collected during ecotourism encounters and from commercial fishers, with limited dedicated field research.
The article, titled Killer whale (Orcinus orca) predation on beaked whales (Mesoplodon spp.) in the Bremer Sub-Basin, Western Australia, was published in PLOS ONE.
The paper was co-authored with Keith Lightbody, Leila Fouda, Michelle Blewitt, David Riggs and Christine Erbe.
For more information on the research, go to www.projectorca.com.au.