Full Breakdown
Octopuses Use Mirrors to Locate Hidden Food
6/6/2026, 9:25:58 PM
Mirror-Based Spatial Navigation Demonstrated
Researchers at Dartmouth College trained three California two-spot octopuses (Octopus bimaculoides) to locate a hidden crab using only a mirror. In a start box facing a mirror, a virtual crab image was projected behind the animal; the octopus had to infer the real location and move to it to receive a live crab reward. Successful navigation occurred in roughly 73 % of trials.
Design and Training Protocol
Lead author Mary Kieseler (Guarini ’25) and senior author Peter Tse acclimated the octopuses to mirrors, then used a live crab in a glass jar visible solely via reflection to teach the mirror-prey association. The test phase replaced the live crab with a projected image, requiring a 90-degree turn or a full 180-degree rotation, sometimes climbing over the box, to reach the reward.
Performance Summary
Across sessions the octopuses chose the correct side in about 73 % of attempts. Overhead tracking of a point between the eyes showed paths were not always shortest, but travel time decreased with experience, indicating learning. Some individuals climbed over the enclosure instead of swimming around it.
Cognitive and Evolutionary Implications
The authors argue that using mirror information implies internal spatial representations, or “mental maps,” which could aid hunting in complex reef habitats. Kieseler notes that octopuses and humans diverged from a common worm-like ancestor 350–500 million years ago, yet both have independently evolved comparable spatial processing—a case of convergent evolution.
Official Statements and Limitations
Kieseler highlighted that the study provides the first evidence of mirror-based prey localization in an invertebrate, expanding known animal cognition. Tse likened the learning process to drivers acquiring rear-view-mirror skills, noting that octopuses must learn this ability. Both researchers said the main gap is the lack of definitive proof of stable internal maps, and they cautioned that further work is needed to determine whether improvements reflect genuine mental mapping or trial-by-trial learning.
Verbatim Quotes
- “Quote Our findings are the first to demonstrate that invertebrates can use mirrors to understand their environment to find prey.” — Mary Kieseler, Guarini ’25, lead author
- “We don’t enter the world knowing how to use a mirror but learn how to use a mirror,” — Peter Tse, senior author
- “Octopuses are among the most evolutionarily distant animals from humans, as our last common ancestor was a worm that lived 350 to 500 million years ago,” — Mary Kieseler
- “Our work suggests that octopuses might also have internal maps, an internal representation of space.” — Peter Tse
What’s Next
The team plans longitudinal tests across additional cephalopod species and varied environmental complexity to assess the durability of mirror-based navigation and to clarify the evolutionary origins of this cognitive skill.
