Killer whales (Orcinus Orca) are well known for their ingenious hunting techniques, which range from generating artificial waves in order to knock seals off ice floes to deliberately beaching themselves in order to catch coastal sea lions. However, orcas in the waters off Patagonia appear to have now raised the sneakiness stakes, after researchers observed a never-before-seen method of ambushing dolphins.
Until now, virtually nothing was known about the diet or predation methods of orcas in the region during the months of February to April, when the sea lion hunting period reaches its yearly low. While it had previously been hypothesized that Patagonian killer whales may have fed on dusky dolphins at this time, the recent sighting – which was reported in the journal Aquatic Mammals – provides the first confirmation of that assumption. Moreover, the way in which the prey is caught highlights the incredible guile and adaptability of orcas.
The paper describes the dramatic pursuit of a dolphin by a pod of orcas on March 3, 2013, during which the killer whales deliberately “herded” their victim towards a “catcher”, who had been silently waiting further ahead for the dolphin to arrive. Falling into the trap, the dolphin was then attacked by the catcher, who launched it five meters (16 feet) above the surface of the water by headbutting it from below. The authors then recount how the injured dolphin, with its “intestines popping out of a bleeding cut on its belly,” was shared between the catcher and her calf.
Interestingly, the calf was observed repeatedly “tossing the prey up into the air”, leading the researchers to suggest that the young orca was attempting to learn the behavior of its mother, indicating that the technique may in fact be taught.
A similar incident was then observed a year later, on March 24, 2014, when the same ambush technique was employed by a different pod of orcas in the region, resulting in a dolphin being flung about two meters (6.4 feet) and knocked unconscious. That the meat was then shared around suggests that the division of food may play an important role in maintaining social coherence within pods of orcas.
The scientists behind this discovery have compared the orcas’ behavior to the “coordinated hunts” performed by chimpanzees in order to catch red colobus, yet insist that such sophistication has not been observed in other social hunters. At the same time, the sighting indicates the importance of dolphin meat in the diet of Patagonian orcas outside of the sea lion hunting season. However, it is not known if similar hunting and feeding patterns apply to orcas in other areas.
Regardless, the ability of these South American-based killer whales to lay traps for other marine mammals confirms their position as the ocean’s most cunning predator.