Under the perceived risk of predation, animals are expected to spend less time sleeping. They show more frequent arousal – perhaps reapportioning sleep to different times of the day (Lima et al., 2005) – or increase the amount, changing the bouts and switching the phase of activity. In the present study, octopuses immediately changed their activity in the presence of both the moray eel and the triggerfish, resulting in an increase in the total amount of activity and a change in bout length. In the presence of the moray eel, there was no temporal spacing.