PS 65-20 - The master of camouflage and risk, measuring giving-up densities of the giant Pacific octopus (Enteroctopus dofleini), in the intertidal of Prince William Sound, Alaska

Friday, August 11, 2017
Exhibit Hall, Oregon Convention Center
Stephanie Chancellor, Ecology and Evolution, University of Illinois at Chicago, David Scheel, Alaska Pacific University, Anchorage, AK and Joel, S. Brown, University of Illinois at Chicago, Chicago, IL

Octopuses are magnificent creatures with uncanny intelligence and ability of great precision when camouflaging to substrate. Although octopuses are extraordinary at hiding, it is unknown how they perceive risk. It has been hypothesized that even though giant Pacific octopus can blend almost perfectly into their surroundings they still prefer kelp or complex habitat to forage. All prey animals, including octopuses, take special measures to evade their many predators, such as hiding in bushes (complex habitat). My goal is to better understand how the giant Pacific octopus (Enteroctopus dofleini) perceives predation while foraging in Prince William Sound, Alaska using giving-up densities (GUD). A forager’s GUD is when they quit harvesting food from a patch due to their costs outweighing their benefits. This can be accomplished with a depletable experimental patch that is set out in an octopus’s environment. Based on how they forage in these experimental patches, I can obtain information about have the perceive risk. A less fearful forager will forage more in a patch compared to a more fearful forager. This allows me to ask questions such as: Where to find food? How many prey items to take? When to quit foraging? How to avoid its many enemies? Patches were made from 2 gallon buckets with 100 golf ball sized wiffle balls as substrate and 10 pieces of shrimp mixed within the substrate. These patches were placed in the subtidal and intertidal zones of Prince William Sound, Ak. Intertidal zones are expected to be percived as risky, with less cover, where as the subtidal habitat is expected to be safer due to more cover available. Patches were placed and recovered every 24 hours and then rebaited.


Octopuses readily foraged from the experimental food patches and left a measurable GUD, shown by food items being removed from patches. GUDs were 10% lower in the subtidal, compared intertidal (Generalized linear model, p-value >0.05). These data help us understand the preferred habitat of the giant Pacific octopus which had previously been unknown. Understanding giant Pacific octopus prefered habitat is important since it will help make management decisions for fisheries and begin to allow us to understand how they interact with their environment. This is also the first time GUDs have been implemented with octopuses and in the intertidal and subtidal habitat.