Abstract
Many ants rely on both visual cues and self-generated chemical signals for navigation, but their relative importance varies across species and context. We evaluated the roles of both modalities during colony emigration by Temnothorax rugatulus. Colonies were induced to move from an old nest in the center of an arena to a new nest at the arena edge. In the midst of the emigration the arena floor was rotated 60°around the old nest entrance, thus displacing any substrate-bound odor cues while leaving visual cues unchanged. This manipulation had no effect on orientation, suggesting little influence of substrate cues on navigation. When this rotation was accompanied by the blocking of most visual cues, the ants became highly disoriented, suggesting that they did not fall back on substrate cues even when deprived of visual information. Finally, when the substrate was left in place but the visual surround was rotated, the ants' subsequent headings were strongly rotated in the same direction, showing a clear role for visual navigation. Combined with earlier studies, these results suggest that chemical signals deposited by Temnothorax ants serve more for marking of familiar territory than for orientation. The ants instead navigate visually, showing the importance of this modality even for species with small eyes and coarse visual acuity.
Highlights
Ants rely heavily on vision for navigation, both for detecting celestial cues that guide path integration and for learning and recognizing the details of their surroundings [1,2,3,4,5]
A more recent experiment suggests that they are less important than visual cues for navigation: colonies were able to find a familiar nest more rapidly than an unfamiliar one, even when substrate cues were exchanged between the routes to the competing nests [12]
Not finding the expected nest, they began a winding search pattern that eventually brought them to the new nest entrance. These lengthy searches led to much longer trip durations after rotation (1986121 sec) than before (28619 sec) (Figure 7C). These results confirm and strengthen earlier work pointing to a dominant role for visual cues in navigation by Temnothorax ants [12,16,17,18]
Summary
Ants rely heavily on vision for navigation, both for detecting celestial cues that guide path integration and for learning and recognizing the details of their surroundings [1,2,3,4,5]. In experiments with Y-shaped bridges, T. unifasciatus foragers prioritized visual cues when these were put in competition with substrate markings, but they resorted to the latter when familiar visual cues were removed [16]. Both kinds of cue were found to matter during colony emigration, when a corps of transporters must navigate repeatedly between the old and new nests [20,21,22]. A more recent experiment suggests that they are less important than visual cues for navigation: colonies were able to find a familiar nest more rapidly than an unfamiliar one, even when substrate cues were exchanged between the routes to the competing nests [12]
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