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Wednesday, May 31, 2017

Watching a Giant

Today was the last day of our spring field trip to northern California and Oregon.  We stopped briefly at Patrick's Point State Park in Trinidad, CA.  It was a productive outing, but one of the highlights was something we weren't even looking for.

I was standing on a rock with fairly deep water to either side, when a very long tentacle appeared.  Then the rest of a large octopus emerged and began to crawl underneath the rock I was standing on!  In the photo below, note the crab in the lower left corner.  Octopuses eat crabs, so it's likely this crab was on high alert:

I turned around, and the octopus emerged from the other side of the rock:

And then it started crawling towards a large pool:


Below, the octopus is in the open as it approached the far edge of the pool.  Giant Pacific Octopuses (Enteroctopus dofleini) are known as the largest octopuses in the world, so we were curious about this individual's size.  

After the octopus left the area, we measured a large sea anemone in the same view (see next section below).  We then estimated the distance from the tip of the leftmost tentacle to the tip of the rightmost tentacle.  Our conservative estimate for that distance (the "arm span") in the photo below is 1.4 meters (4.6 feet).  Although that's impressive, we realize it is likely this octopus could extend its tentacles much farther.  (Some of the largest individuals have measured 15-20 feet across!)

Here's one more image while the octopus paused before jetting backwards and disappearing below another boulder.  For scale, note the other familiar animals nearby, e.g., the Ochre Sea Star on the right side of the image and a few Purple Sea Urchins under a ledge above the octopus.  The Giant Green Anemone on the rock directly in front of the octopus is ~11 cm (~4.3 inches) across.  (The anemone's tentacles are withdrawn, so it looks like a soft, army-green lump.)

Although the total amount of time that passed while we watched this octopus was only ~2 minutes, it was a memorable experience that felt much longer.  We've seen Giant Pacific Octopuses in aquariums, but this was the first time we've observed a living animal in the wild.  We're so grateful for these gifts from the ocean.