Seven Octopus cyanea Gray (Mollusca: Cephalopoda) were observed for 120 hr over a period of 60 days in two Hawaiian reef ponds under near natural conditions. O. cyanea is crepuscular with activity peaks at 06.00 and 18.00 hours. Hunting excursions may extend up to 50 m from the home and may be 1 hr in duration. O. cyanea will pursue and catch crabs it sees but its most common method of hunting is speculative, the octopus pouncing on likely areas with the web spread and feeling beneath the web for prey. These leaps are made every 1 to 2 m along the hunting route. Crabs captured appear to be paralysed immediately and carried to the home to be eaten. Several octopuses will use a single hunting ground and homes may be used by more than one octopus successively. Large octopuses are dominant over smaller ones and will occasionally pursue them. Crab populations were reduced and algal growth was enhanced within the experimental area. O. cyanea is a major predator on crabs and an important member of the coral reef community. © 1969.
