Dive Dry with Dr. Bill

111: CAUTION- Construction Zone

As I walk up Metropole, I can't help but notice the earth-moving going on at the site of the old Hotel Glenar. Construction is an important activity underwater as well as in our own community. Many marine critters actively build their own homes to shelter from potential predators. The same weekend I discovered the giant scallop (yet to be identified by the Scripps scientists), I encountered the Dive Park equivalent of Pete Edwards and Fine Line Construction- an octopus. Being the ever patient diver and biologist that I am, I sat and watched this tireless worker over the course of two dives.

When I first encountered it, the octopus was facing off against a kelp bass. These fish are known to eat octopus (making them a competitor of mine for food since I, too, enjoy these cephalopods). However this octopus had no intention of becoming a mid-day snack, and it fended off the bass successfully. That's when the work began. I usually don't see octopi out on the sandy bottom, but such sightings have been common this year. This individual had selected a spot near an outcropping rocky reef and started working in earnest to excavate a shelter hole in the sand at its base. Apparently it was a rush job since I didn't see any permits posted.

As I watched, the octopus would hunker down in the hole and show signs of activity for a minute or so. Then it would slowly rise out of the hole carrying the sand, gravel and small rocks it had excavated. It held this material in its mantle under the webbing between its eight legs. Once out of the hole, it would extend itself across the bottom and explosively expel the sand and other debris. If it were carrying larger rocks, it would carry them and gently deposit them well away from the hole itself. At least it would usually do this. One time it didn't reach far enough and the rock slowly rolled back towards the hole.

The octopus was determined and worked without stopping. No mandatory coffee breaks for this laborer. On my first dive observing it, I started to run low on air and had to do my safety stop and ascend. After a 30-minute surface interval topside talking to other divers, I descended again to see if the octopus was still constructing its den. Of course it didn't have the benefit of one of Pete's backhoes, so it was still hard at work. You'd think with eight arms, it could really do wonders with just a shovel. I settled back down near it and gradually moved in closer to allow it to reacclimate to my presence. The result was a nice behavioral sequence of the octopus digging its hole. I even caught the tail end of a cave in, which forced the eight-armed wonder to intensify its digging.

In the past I have observed many octopi in the park. Although I usually see them in rock crevices, recently I've seen several in holes dug in the sandy bottom. Perhaps the local housing stock in the Dive Park is as limited as it is topside in Avalon. This was the first time I've actually observed such a project in the construction stage. Several years ago I filmed another octopus under a large rock overhang. That individual was also creating a shelter, but using a different set of construction skills. Instead of digging like a protoplasmic backhoe, it was excavating pebbles from under the large rock. As I filmed it, it built a stone wall between us using the pebbles it removed. This one must have been in the bricklayer's or stoneworker's union. As it enlarged the hole under the rock, it also built the protective wall in front. Good use of construction debris if you ask me.

The next weekend I returned to look for my sandy bottom octopus. The hole was still there, but it was partially filled in. It appeared that the octopus had experienced one too many cave ins and decided to seek shelter elsewhere. Perhaps he should have done an EIR and gotten those building permits. Maybe he became an apprentice to the "brick layer" to learn how to build a more permanent shelter. After all, octopi are considered quite intelligent and are quick learners. I've got some stone work I'd like to get done at the house, but I have a feeling Fine Line would be a better choice since its workers are more adapted to the terrestrial environment.

© 2004 Dr. Bill Bushing. Watch the "Dive Dry with Dr. Bill" underwater videos on Catalina Cable TV channel 49, 10:00 AM and 5:00 PM weekdays.

Octopus emerging from newly forming hole with debris; with debris held in its mantle;
extending out from entrance to hole; expelling excavated dirt.

This document maintained by Dr. Bill Bushing.
Material © 2004 Star Thrower Educational Multimedia