Some species of octopus and of fish seem to share leadership when hunting prey together, according to an article published in Nature Ecology & Evolution. The discoveries broaden our understanding of the sophisticated inter-species social life of octopuses and fish.
Octopuses, which are frequently considered solitary animals, have been observed hunting in groups with different species of fish — including several goatfishes and blacktip groupers — to share prey such as mollusks and crustaceans.
Earlier observations of these groups suggested that the octopus led the hunt, while the fish typically followed it. More complex group interactions between octopuses and fish have been suggested, but these are difficult to document.
Eduardo Sampaio and colleagues followed groups of hunting octopuses and fish during diving expeditions in the Red Sea. They observed hunting groups composed of one-day-old octopuses and different species of fish, including goatfish and blacktip groupers, totaling 13 groups.
After collecting and analyzing data from 120 hours of underwater dives, the authors report that leadership is shared among groups for different types of decisions. For example, the goatfish specialized in exploring the environment — deciding where the hunting group moves — while the octopus decided if and when the movement would be made.
This joint effort leads to greater hunting success compared to the octopus or the fish acting alone, depending on the group’s composition. Sampaio and colleagues also observed aggressive control mechanisms among group members, including fish moving toward others, charging at them, and octopuses moving fish toward the outer areas of the group, delivering blows.
The authors note that, although other types of mixed-species hunting groups are known — such as groups of badgers and coyotes, of mixed birds and of morays and groupers — these seem to be less flexible in using social information to change strategy than octopus–fish hunting groups.
