Navigation without vision: bumblebee orientation in complete darkness

In flight cages, worker bumblebees (Bombus impatiens) spontaneously explored the surroundings of their nest and foraged in complete darkness, by walking instead of flying, from feeders up to 150 cm away from the nest. This behaviour was wholly unexpected in these classically visual foragers. The finding provides a controlled system for dissecting possible non-visual components of navigation used in daylight. It also allows us to isolate navigation mechanisms used in naturally dark situations, such as in the nest. Using infrared video, we mapped walking trails. We found that bumblebees laid odour marks. When such odour cues were eliminated, bees maintained correct directionality, suggesting a magnetic compass. They were also able to assess travel distance correctly, using an internal, non-visual, measure of path length. Path integration was not employed. Presumably, this complex navigational skill requires visual input in bees.