Octopuses learn mirror use to track hidden prey

octopuses learn – Researchers report that California two-spot octopuses (Octopus bimaculoides) can learn to use a mirror to find a hidden crab—skipping the mirror pit stop after repeated trials and making correct choices using reflections even in a setup that blocked other visu

On a tank’s front edge, a mirror creates a version of reality that isn’t quite real. For most animals, that difference is confusing at best, irrelevant at worst.

But in experiments led by Mary Kieseler, a neuroscientist at the University of Fribourg in Switzerland, California two-spot octopuses learned to treat that reflected view like a map. The work was reported June 3 in Current Biology.

Kieseler had originally been thinking about the classic “mirror test”—the one used to see whether an animal can recognize itself. But underwater, she said, the logistics of mirror self-recognition are challenging. So instead of jumping straight to self-recognition. she and her team asked a different question first: could octopuses learn to use mirrors for something they’re already excellent at—hunting prey?.

They started with three wild-caught octopuses. The animals were habituated to a mirror that covered half their tank. For this introductory phase. the researchers let them hide from the mirror and even explore the other half of the tank behind it. Once the octopuses were comfortable with seeing their reflection and eating in front of the mirror, the task began.

The scientists placed a hidden jar with a tasty crab inside where the snack could be found using only the reflection in the mirror. The sequence was deliberately simple in concept: the octopus should ignore the “real” location and use the mirror to locate where the prey appeared.

At first, the octopuses approached the mirror—then turned around as if the reflection were a waypoint rather than a destination. But after about 10 to 12 trials, each animal learned to crawl directly to the crab without the mirror pit stop.

There was still one problem: using real crabs left open the possibility that the octopuses were relying on smell or another nonvisual sense to hunt, rather than understanding the mirror’s visual trick.

So the team built a final test that tried to make reflection the only route to a correct choice. Instead of real crabs, they used virtual ones. Each octopus was placed in a small three-sided chamber that walled off its view of anything other than a mirror at the tank’s front. Behind the chamber. a screen played videos of a crab appearing to move along either side of the back wall. producing a reflection that the octopus could see.

To earn a real crab reward, the octopus had to navigate out of the chamber and move to the correct side.

Getting the octopuses to work at all was hard, Kieseler said. “They did plenty of trials where they just fell asleep or sat in front of the mirror.” Each octopus completed only about one trial per day.

Even with that limitation, the results were clear. The octopuses chose the correct side in about 73 percent of the trials with virtual crabs. In 59 percent of their correct trials. they didn’t just go to the right place—they climbed over the side walls of the chamber to reach the crab stimulus rather than approaching the mirror.

To Trevor Wardill. a neurobiologist at the University of Minnesota in Minneapolis who was not involved in the research. the pattern matters because it suggests something more than a reflex. “This shows that octopuses can understand how a mirror represents the location of an object. ‘rather than just going impulsively to the mirror reflection hoping to get a reward. ’” he said.

Taken together. the experiments suggest octopuses can adapt their navigation strategies in complicated environments when mirrors are part of the toolset. And for Kieseler. the next step is obvious: now that octopuses are known to learn mirror use. she hopes researchers will bring the mirror self-recognition test back into the tank.

octopus mirror test Current Biology Octopus bimaculoides Mary Kieseler Trevor Wardill mirror learning prey hunting marine cognition