Reorientation by geometry in bumblebees

Human and non-human animals are capable to make use of geometric information (metric and sense) specified by the macroscopic layout of surfaces to reorient in an environment. It is debated, however, whether geometric information is encoded by explicitly computing the layout of surface geometry of by matching images of the environment. View-based spatial encoding is generally thought to hold for insect navigation and, very recently, evidence for navigation by geometry in ants has been reported. Here we tested bumblebees (Bombus terrestris) abilities for spatial reorientation. After spatial disorientation, bumblebees had to find one of the four exit holes located in the corners of a rectangular enclosure. Bumblebees systematically confused geometrically equivalent exit corners. When one wall of the enclosure was made of a different colour, bumblebees conjoined this featural information with geometric information to find the uniquely correct exit corner. When after training geometric and featural information were set in conflict by displacing the feature from one wall to another, bumblebees appeared to rely on both geometric and non-geometric information depending on whether the feature was located near or far from the goal during training, and whether the change in the location of the feature was associated with an increase or a decrease in its size from training to test. Results are discussed in relation to the hypothesis that bumblebees reorient by matching images at different spatial scales.