Long-term high-density occupation of a site byOctopus tetricusand possible site modification due to foraging behavior

We report observations of wild octopuses (Octopus tetricus) living in close proximity at a site centered on a single den that has been occupied since at least November 2009. Numbers observed on survey dives range from 2 to 11 (average of 5.48). We hypothesize that long-term occupation of the site has led to its physical modification through the accumulation of shells brought in during foraging, and that this “ecosystem engineering” has in turn resulted in higher densities being viable at the site.