Orcas seen killing and eating beaked whale and sevengill shark

Orcas seen killing and eating beaked whale and sevengill shark
(A) Observation 4: The beaked whale’s head clear out of the water allowing for a positive identification of strap-toothed whale (Mesoplodon layardii). (B) Observation 4: The beaked whale with its skin stripped off the body from the rostrum to the dorsal fin. Credit: PLOS ONE (2016). DOI: 10.1371/journal.pone.0166670

(Phys.org)—Two unrelated and rare instances of orcas killing and eating other ocean creatures has been witnessed and documented—one off the coast of California, the other off the coast of Australia. In one incident, the action was caught by a drone pilot out for a day of fun—he captured video of an orca killing a sevengill shark that was subsequently passed around for consumption by several other orcas. In the second, a team of researchers studying orcas off Australia's southern coast reported observing orcas capturing and killing beaked whales on four occasions. They have published their findings in a paper they have uploaded to the open access site PLOS ONE.

Despite their notoriety among the , scientists still do not really know a lot about , aka killer whales, particularly those in small groups, such as those that live in the waters around Australia. Scientists have categorized orcas (members of the dolphin family) into three main groups based on where they live: offshore, transient and resident. Offshore orcas are generally the smallest, living, as their name implies, relatively close to a shoreline and congregating in large groups—but they have not been well studied. Both of the recent rare feeding incidents involved offshore orcas, which is likely why their activities were considered surprising. The whale killing was the first of its kind ever recorded. It is not known if that is because humans have not been around to see it happen before or if the orcas were changing habits due to a changing environment. Killing whales is not easy for orcas, the researchers report; they chased their prey for two or more hours to tire it out before drowning and then skinning it.

The shark attack was captured by a camera aboard a drone piloted by Slater Moore—it involved two adult females and two calves. Moore was out on a sightseeing boat when he launched his drone and captured the action a short distance away—he told reporters he believed the shark was approximately five feet in length. Few such examples of hunting and feeding have been reported with orcas because they usually carry out such activities underwater. Some have speculated that the reason the happened on and near the surface was because the adults were trying to teach their young how to hunt.

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More information: Rebecca Wellard et al. Killer Whale (Orcinus orca) Predation on Beaked Whales (Mesoplodon spp.) in the Bremer Sub-Basin, Western Australia, PLOS ONE (2016). DOI: 10.1371/journal.pone.0166670

Observations of killer whales (Orcinus orca) feeding on the remains of beaked whales have been previously documented; however, to date, there has been no published account of killer whales actively preying upon beaked whales. This article describes the first field observations of killer whales interacting with, hunting and preying upon beaked whales (Mesoplodon spp.) on four separate occasions during 2014, 2015 and 2016 in the Bremer Sub-Basin, off the south coast of Western Australia.

Journal information: PLoS ONE

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