2015 Darwin Science Expedition - Day 21 - A romantic dance with a mortal end
Great Chagos Bank Eagle Island
This morning’s dive provided us with a fascinating display from a pair of octopus. We dropped to the eastern side of Eagle Island and although the plan was to follow a shallow survey path along the reef drop off I was distracted shortly after entering the water when some movement amongst the coral heads caught my eye.
On closer examination I realized that a pair of octopus were squaring up to each other a few feet apart amongst the coral beneath us. I circled closer expecting the octopus to jet away or squeeze themselves under the nearest coral head for cover. Octopus are usually shy creatures and tend to retreat as a first resort – although you can occasionally tempt them out as they are very curious creatures too (watch this video of an octopus I filmed in Madagascar to see what I mean).
On this occasion both octopus seemed completely oblivious to me so I hunkered down a shot distance from them and started filming. Which is when I realized something more was on the go here…
As I watched the octopus furthest from me became highly energized. Its arms spiralling and caressing its body. At the same time the octopus closest to me was slowly extending an elongated arm toward the displaying partner opposite. It dawned on me that I was witnessing a courtship display.
The dancing octopus furthest from me was the female signalling her excitement at the males interest as he extended his hectocotylus, an elongated arm equipped with a tube for delivering sperm packets, toward her. The process was fascinating to watch. The male unwinding and lengthening his arm, slowly waving it closer and closer to the female. And then gently touching her and feeling the way up and into her mantle. Here the sperm packets are transferred and the female can store them until her eggs are ready to lay.
VIDEO https://www.youtube.com/watch?v=3uC4adciMYk
I expected the process to last no more than a few minutes and was waiting for the behaviour to end so that I could film it’s closure but after an hour I had to call time on the dive and return to the surface. Although the female had pushed away the males hectocotylus several times – on each occasion he had extended it again and the female had accepted his advances.
On reading up a little more on this octopus mating ritual later in the day it was sobering to realize that this is the opening ritual in the final act of an octopus life. Shortly after mating the males reach the end of their life cycle and die. The female lasts a little longer, laying the eggs in a suitable cave or overhang, she watches over her clutch until they hatch and then also reaches the end of her life span and dies. A romantic dance with a mortal end.