Hunting in a tough neighborhood: juvenile octopus interactions with territorial and follower fish

Michaella Pereira Andrade, Jennifer Mather, Charles MD Santos

Octopuses are keystone species in shallow-water marine ecosystems. Although researchers mostly focus on predator-prey interactions, many non-lethal yet non-neutral interactions occur, particularly among fish. These range from possible cooperation through kleptoparasitism and scavenging to occasional octopus predation on an unwary fish. We evaluated some of these interactions using video recordings of juvenile Octopus insularis interacting with 10 fish species on Brazilian reefs, forming a repertoire of behaviors, examining when they were used, and tracking the consequences using Lag Sequence Analysis. We observed 101 interactions with seven non-territorial and three territorial fish species. Fish territoriality had a significant impact on fish behavior and octopus behavior. The duration of interactions was significantly longer in non-territorial fish. Interactions with territorial fish involved faster approaches and higher rates of behavioral change for both animals and were characterized by fish ‘Jabs’ and ‘Swipes’, and octopus Flinches and arm Slaps. Interactions with non-territorial fish were characterized by fish Follow and Circle, and the octopus continuing its hunt. Lag Sequence Analysis confirmed distinct and predictable behavioral sequences for each interaction type. These results demonstrate that during foraging octopuses need to navigate a complex set of relationships that are frequently conflictual.