By: Kelley Voss
Hi! My name is Kelley, and I am beginning my fourth year studying octopuses as a Ph.D. student at the University of California, Santa Cruz. (Yes, researchers use “octopuses.” If you want to be very pedantic, the Greek plural is “octopodes.”) I have been coming to Wrigley for different programs and research projects since 2012, but now as a Fellow, I am conducting my own really exciting behavioral work that will expand what we know about how octopuses fight back against predators. We understand how octopuses camouflage themselves, and how they ink, use jet propulsion, and crawl into small holes to escape predators unharmed. However, we currently have no published research about how octopuses retaliate when they’re attacked by a predator; for example, if they are bitten by a California moray eel (Gymnothorax mordax), which commonly eats octopus arms. This is where my work comes in: I observe the interactions between the California two-spot octopus (Octopus bimaculatus) and a moray to discover how octopuses may be using, and risking, their arms in self-defense. Here is what I’ve been doing in a typical day of my work, guest starring my REU student summer mentee, Nikita Sridhar.
Kelley poses with an octopus just before collecting size measurements and determining the sex
Niki and I usually start our day with a nice morning dive to collect octopuses. We swim on SCUBA through the shallow rocky reefs, looking carefully in every single crack and crevice using our dive lights. After all these years, I’m still so excited every time I catch a glimpse of a little octopus eye with a horizontal, bar-shaped pupil or a row of suction cups! Niki holds the collection bag under the hole while I coax the octopus out of its den by squirting a white vinegar solution into the hole. This is like a “stink bomb” that annoys the octopus but doesn’t hurt it. I guide the octopus into the bag as it leaves the den, and we’re ready to go! We bring each octopus back to the Wrigley waterfront, where we collect size measurements and determine the sex of the octopus. The octopus will then hang out in a mesh cube in a tank with an octopus-approved snack (a piece of shrimp or anchovy!) for about a day until it’s time for the behavioral trials to start.
A mid-sized California two-spot octopus (Octopus bimaculatus), which is a species common around Catalina Island.
Niki and I conduct trials in the early evening, which is when morays begin to be most active. We have four tanks, each housing one moray that is under two feet long. For each trial, we simply put an octopus into a tank with a moray and allow them to interact freely for an hour, at which time we separate them. We record all trials from two different angles, from above and the side, so we can confidently determine which arms the octopus used to distract or fight back against the moray. If the octopus actually loses arms, we record details about the injuries and then euthanize and preserve the octopus for a different research project. Uninjured octopuses get to go back where we found them.
Kelley looks into a tank containing an octopus and a moray after a behavioral trial.
When Niki and I are not in the water or conducting trials, we’re analyzing the video we recorded to collect behavioral data, because the first rule of octopus fight club is, “record EVERYTHING.” Even if the octopus doesn’t lose an arm in a trial, we are still able to see which arms it uses in a situation that has escalated, and that’s important too! This work is exciting because it fills a gap in our knowledge about octopuses, and also about how energy moves through the Catalina Island food web. About two of every three octopuses I find in the Two Harbors area has at least one arm that has been lost and is in some stage of regrowth. However, we really don’t know anything about the causes or effects of this very common occurrence. Interactions between morays and octopuses are hard to observe, for example, because they generally happen after dusk, when morays hunt, often in rock crevices instead of out in the open. The most interesting thing to me about these interactions is that octopuses don’t die when they lose an arm—they just grow another one! This seems to mean that the way energy flows up the food chain, from the sun to algae, to grazers, to larger and larger predators, doesn’t require an animal to die to be part of this process. I will use this study as part of my effort to answer bigger questions about how octopuses use their many arms, and how the loss of these arms may affect both themselves and their ecological communities.
If you want to learn more about my work, I’ll be giving a talk on Saturday, July 27th at 10:00 AM here at the Wrigley Institute, or you can visit my website: www.kelleyvoss.com. I’m always excited to talk about what I think are some of the most fascinating animals on the planet! I’d also like to thank Niki, as well as REU Elena Pilch, my labmate and fellow Fellow Kat Dale, and our advisor Dr. Rita Mehta for all of their continued help in making my research happen.