Effects of Crowding on the Social Behavior of Cuttlefish (Sepia officinalis).

To evaluate the effect of crowding on cuttlefish (Sepia officinalis), a benthic cephalopod, the behavior of captive-reared cuttlefish was monitored for a period of 1 month. One group of 6 cuttlefish was housed in a tank 6.1 m in diameter (4.87 m2 per cuttlefish); another group of 6 was housed in a tank 1.5 m in diameter (0.29 m2 per cuttlefish). Cuttlefish spaced themselves within each tank so as to avoid other cuttlefish. Those in the small tank hovered more and sat on the bottom less, showed more zebra patterns and Intense Zebra Displays (associated with aggression), ate less food, and were displaced by other cuttlefish 3 times as often as those in the large tank. Most aggression resulting in displacement was directed at females by males and sometimes resulted in physical injury to the females. Subjects' body patterns were highly predictable, using the following variables: activity, sex, tank, and number of nearby cuttlefish. Analysis of results indicated that behavior was strongly affected by housing conditions and suggested that this species is probably semi-solitary in natural conditions.