Spatially coordinated predation with division of labor increases feeding success in killer whales.

Group hunting is widespread among large vertebrates and is known to confer considerable advantages compared with foraging alone. Yet, the mechanisms underlying group hunting, including how social predators are organized during a hunt, are largely unknown for marine predators. Using drone videos, we tracked the predatory behavior of killer whales along the Norwegian coast to test the hypothesis that group hunting is organized in space, both in terms of individual roles and interactions with conspecifics. Taking advantage of shallow water hunts that reduced the interactions to a 2D horizontal plane, we reveal that whales using underwater tail slaps (i.e., "strikers") to stun herring are more likely to hunt near a neighbor (i.e., a "helper") rather than alone, and such "joint slaps" show higher feeding success (measured as feeding bout duration) than "alone slaps." At the onset of a joint slap, the position of the whales follows a specific geometrical pattern. Whales preferentially take roles as strikers or helpers, with division of labor determined by size: larger individuals predominantly act as strikers in line with their higher feeding success compared with smaller whales. Both striking and helping behaviors are more likely to be observed in males than in females. Individuals involved in joint slaps have preferred partners, with whom they share multi-decadal social bonds, likely allowing repeated opportunities to practice and learn to bestow enhanced geometric positioning and hunting success. These findings highlight the importance of social organization, long-term bonding, and developmental learning in the cooperative hunting of marine mammals. VIDEO ABSTRACT.