Hunting in a complex neighborhood: Juvenile octopuses' interactions with territorial and follower fishes

Octopuses are keystone species in shallow-water marine ecosystems. While research has focused on predator-prey interactions, the non-neutral interactions between octopuses and fishes have not been well characterized. These range from possible cooperation, kleptoparasitism, and scavenging to occasional predation on unwary fishes. To address this gap, we analyzed video recordings of juvenile Octopus insularis interacting with 10 fish species on Brazilian reefs, compiled an ethogram, and tracked the outcomes of interactions using Lag Sequence Analysis. We observed a total of 101 interactions between octopuses and seven non-territorial fish species and three territorial fish species. Fish territoriality significantly affected the behavior of both fishes and octopuses. The duration of interactions was significantly longer in non-territorial fishes. Interactions with territorial fishes involved faster approaches and higher rates of behavioral change for both animals and were characterized by 'Jabs' and 'Swipes' by fishes, and 'Flinches' and arm 'Arm slaps' by octopuses. Interactions with non-territorial fishes were characterized by 'Follow' and 'Circle' by fishes, and the octopuses continuing their hunt. Lag Sequence Analysis confirmed distinct and predictable behavioral sequences for each interaction type. The presence of territorial fishes also affected octopus body patterning, with the 'Half blotch' - a defensive body pattern - occurring only in interactions with territorial fishes. These results demonstrate that during foraging, octopuses need to navigate a complex set of conflicting interactions.