Aplysia fasciata were observed in a number of environments. They were usually aggregated. Animals were occasionally buried in sand. Aplysia were less mobile and more deeply hidden when waves were strong. Aplysia swam only in a calm environment. A wide variety of seaweeds were eaten, but the most common food was Ulva lactuca. Food arousal and satiation occur in the field. Often the pattern of feeding was a gradual slowing down and eventual cessation of eating; however, many meals deviated from this pattern. Appetitive behaviors preceding mating as a male were similar to those preceding eating. Aroused animals mated as males, while passive animals mated as females; mating as a male produced arousal, expressed as an increased likelihood to respond to food or to mate as a male. Two males could simultaneously impregnate one female. Animals mate in large groups, constantly changing partners. Mating groups occur in linear chain, branched chain, and closed chain configurations. Egg laying and egg masses were observed in areas inhabited by animals. Inking was never observed without exprimenter intervention, even when a crab attacked an Aplysia.