Social Organization and Use of Space by Octopus Joubini in a Semi-natural Situation

To study how the species occupies its living space, two groups of Octopus joubini (4–6) were each kept in a 1 m² tank for 4 months. Occupancy of different areas in the 1 m² tank (monitored with the aid of a 16-square grid) suggested dominance relationships. Occupancy of all areas was not randomly distributed (Chi-square < .01). But animals did not spend most of their time in an area separate from the others, as they would if they were territorial. All octopuses were most attracted to corners, and spent a minimal percentage of time in center areas (ANOVA significant at <.01). Interactions between octopuses of the same sex were tabulated; in most cases a clear “winner” emerged and this dominance also appeared size-based. Occupancy of plexiglass box “homes” was also monitored; octopuses changed homes frequently but the largest stayed in one home more (t-test < .01 for one group), suggesting dominance of the largest animal. It is concluded that in this situation (and possibly in their natural environment) Octopus joubini are not territorial but rather set up dominance relationships.