Determination of the diet of Octopus rubescens Berry, 1953 (Cephalopoda: Octopodidae), through examination of its beer bottle dens in Puget Sound

Den middens have been used to determine the diet of several species of octopuses, but are not available for the red octopus (Octopus rubescens Berry, 1953). As a result, its diet in the wild is poorly known. To determine their diet, O. rubescens were collected in beer bottle dens, evicted from the bottles for measurement, and released. The shell contents of the bottles were then sieved, identified and compared to those from bottles not containing octopuses. The shell contents of bottles containing octopuses had significantly more species and significantly more shells than bottles without octopuses. In this mud/sand area, the octopuses were consuming predominantly the gastropod Olivella baetica. Beer bottle trash on the sea floor is a non-polluting den resource for O. rubescens, and is shown here to be a valuable tool for diet analysis.