Some Aspects of Hole-Boring Predation by Octopus vulgaris

Octopus vulgaris prey upon many gastropod species by boring holes in the shell, weakening the prey with a venom, removing the entire prey, and eating it. When offered Strombus raninus the Octopus quickly grasped the conch with one or a few arms, checked for occupancy by inserting an arm tip into the aperture, and passed the shell under the web to the mouth. The shell was held against the buccal mass by the circumoral suckers and rasped repeatedly with the radula, repositioned, and rasped again. There were brief pauses of apparent inactivity between the periods of active rasping. The shell was penetrated at an approximate maximal rate of 1.25 mm per hour. The boreholes averaged 0.93 mm in outer diameter, 0.47 mm in inner diameter and 0.88 mm in depth. The boreholes were extremely variable in shape, size, and position on the spire. There was a marked preference for individual animals to bore in a particular sector of the spire. Apparently the animals orient the shells by using the lip as a point of reference because lipless shells had the boreholes randomly distributed around the shell.