Killer whales. The name alone is enough to strike fear in even the steeliest of hearts. Also known as orcas, these apex predators are sometimes referred to as “wolves of the sea” and are found across the globe. Like wolves, Orcinus orca in the Northern Hemisphere are known to hunt in packs, teaming up to subdue larger prey and Orcas and their prey in the Northern Hemisphere have been well studied. However, until recently, little research has been done on the predatory tactics or prey of killer whales living off the Western coast of Australia.
In a recent study published in PLOS ONE, a team of researchers took a total of 141 field trips over the course of three years to the Bremer Sub-Basin off the southern coast of Western Australia to observe killer whales and their prey.
A detailed tracking of all the observed attacks in Bremer Bay
On February 25th 2014, the group struck lucky as a group of at least 20 killer whales was sighted off Bremer Bay, followed shortly after by a mesoplodont beaked whale (Mesoplodon spp.). Killer whales have been known to feed on beaked whales, but a direct attack had never been observed. What happened next reads like an opening to a horror movie, as approximately five killer whales (pictured above) flanked the beaked whale for over 67 minutes before the first attack occurred. The subsequent action was ferocious: the killer whales began ramming, striking, and biting the beaked whale. Occasionally, the killer whales would swim on top of the beaked whale and submerge it below the water, where more attacks apparently took place. Four minutes later, it was all over. The beaked whale was last sighted being pushed below the surface by three killer whales. The killer whales took short dives to the area where the beaked whale was last seen and blood was observed in the water.
On 18th February 2016 the fourth observed attack was a violent affair
Over the course of the three years out in the field the authors observed three more attacks on beaked whales. Each attack resembled the first observation in many ways, as seen in the pictures above. However, perhaps the most interesting common observation was the makeup of the killer whale group. Researchers observed adult females, sub-adult males and females, and juveniles in the immediate group, while the adult males kept their distance. This favoring of females and children is consistent with how killer whale prey elsewhere in the Northern hemisphere, however this study marks the first time this female-juvenile arrangement has been observed in the Southern hemisphere and possibly the first observed attack on a beaked whale.
Citation: Citation: 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. doi:10.1371/journal.pone.0166670