Katherine Harmon Courage, author of the recent book Octopus! The Most Mysterious Creature in the Sea, summarizes here the results of a study on octopus dietary preferences. Previously, octopus diet preferences were inferred from the collection of shells and bones around an octopus's den (this habit of octopuses-- arranging shells, bones, and sometimes shiny pieces of glass or pottery in front of its den-- inspired the hit Beatles song "Octopus's Garden"). however, that only gives evidence of hard-bodied prey items, and with little to no time-of-meal information! In this study, researchers used a method including observation and digestive tract analysis.
They found that octopuses prefer eating crab before mating; just like humans, they have preferences that shift with circumstances. It is possible that energetic demands shape their food choices over time.
This study joins a growing body of fascinating research about octopus cognition and behaviour. Past studies have demonstrated that octopuses unscrew jars, escape from almost any state of captivity, pass basic cognitive tests, and even play; they are the cognitive equals of many vertebrates! This is particularly perplexing because conventional theory says that intelligence is seen in long-lived, social vertebrates (dolphins, primates, elephants, birds); octopuses, however, are short lived, spineless, asocial beings. Further still, each of their 8 arms has a "mind of its own," with neurons spread out throughout its body so that its arms are, in a sense, autonomous beings. It is possible that the octopus form of "thinking" is totally alien to what we are used to seeing in ourselves and our vertebrate relatives.
In short, we are only beginning to chip away at the complete mystery of the octopus mind. If you haven't already, I recommend setting up a google alert for "octopus cognition." It's definitely worth it,
Studying octopuses’ dietary preferences, however, can be a tricky endeavor. Scientists have long relied on counting and classifying shells and bones in an octopus’s stomach or around its den. But as the researchers of the new paper point out, “only prey with hard pieces can be identified.” In the case of ingested animals, the identification is often hampered because “the mechanical action of the beak” breaks down many would-be calcified clues. And for crustaceans, such as large crabs and lobster, the octopus can pre-digest the animal tissue inside the exoskeleton before slurping it out—leaving the traces of that meal to be carried away by the currents.