How Ants Use Vision When Homing Backward
Sebastian Schwarz 5, Michael Mangan 5, Jochen Zeil, Barbara Webb, Antoine Wystrach 6, Antoine Wystrach
5Co-first author
6Lead Contact
Published Online: January 19, 2017
Publication stage: In Press Corrected Proof
Open Access
Open access funded by Engineering and Physical Sciences Research Council
Article Info Publication History
Published: January 19, 2017 Accepted: December 9, 2016 Received in revised form: November 10, 2016 Received: September 26, 2016
User License
Creative Commons Attribution (CC BY 4.0)
Highlights
• Backward-walking ants rely on celestial but not terrestrial cue memories
• Correction of direction based on terrestrial cues occurs after peeking forward
• The retrieved direction can be transferred into a compass frame of reference
• Ants can decouple their travel direction from their body orientation
Summary
Ants can navigate over long distances between their nest and food sites using visual cues [ 1, 2 ]. Recent studies show that this capacity is undiminished when walking backward while dragging a heavy food item [ 3–5 ]. This challenges the idea that ants use egocentric visual memories of the scene for guidance [ 1, 2, 6 ]. Can ants use their visual memories of the terrestrial cues when going backward? Our results suggest that ants do not adjust their direction of travel based on the perceived scene while going backward. Instead, they maintain a straight direction using their celestial compass. This direction can be dictated by their path integrator [ 5 ] but can also be set using terrestrial visual cues after a forward peek. If the food item is too heavy to enable body rotations, ants moving backward drop their food on occasion, rotate and walk a few steps forward, return to the food, and drag it backward in a now-corrected direction defined by terrestrial cues. Furthermore, we show that ants can maintain their direction of travel independently of their body orientation. It thus appears that egocentric retinal alignment is required for visual scene recognition, but ants can translate this acquired directional information into a holonomic frame of reference, which enables them to decouple their travel direction from their body orientation and hence navigate backward. This reveals substantial flexibility and communication between different types of navigational information: from terrestrial to celestial cues and from egocentric to holonomic directional memories.
Keywords:
insects, ants, navigation, egocentric memories, directional frame of reference, holonomic, backward motion, landmarks, celestial compass
Received: September 26, 2016; Received in revised form: November 10, 2016; Accepted: December 9, 2016; Published: January 19, 2017
© 2016 The Author(s). Published by Elsevier Ltd.
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