Cooperative feeding and foraging lateralization by Eden's whales off southern China

We investigated surface feeding behaviors of Eden's whales (Balaenoptera edeni edeni) in northern Beibu Gulf, southern China, between April 3, 2018, and April 26, 2021. During 122 days at sea, 1,065 individual feeding events were recorded, and eight feeding behaviors were identified: two nonlunging (tread‐water and/or trap‐feeding, 7.7%, and a novel behavior we call “pirouette feeding,” 15.3%) and six lunging (right lateral lunging, RLL, 10.9%; left lateral lunging, 0.2%; upright lunging, 6.3%, vertical lunging, 18.5%; inverted lunging, 0.3%; cooperative lateral lunging, COL, 40.9%). During COL, 2–8 whales swam clockwise around a fish school and simultaneously performed RLL on surfacing—the first cooperative feeding behavior recorded for a Balaenoptera whale. Five lateralized feeding behaviors (entailing either a left or right rotation on the long‐body axis) accounted for 65.8% of individual feeding events, with a strong right‐side bias (99.7%). Lateralized behavior is prevalent in many vertebrates, including several species of rorquals, and we suggest that the right‐biased foraging lateralization among rorquals specifically allows them to keep their right eye on their prey (i.e., a sensory versus motor lateralization), and that this shared asymmetry among conspecifics may have preadapted Eden's whale for cooperative foraging.