title: How Ants Use Vision When Homing Backward.
abstract: 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. VIDEO ABSTRACT.
authors.affiliation: School of Informatics, University of Edinburgh, 10 Crichton Street, Edinburgh EH8 9AB, UK.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Schwarz
authors.affiliation: Centre for Autonomous Systems, University of Lincoln, Brayford Pool, Lincoln LN6 7TS, UK.
authors.forename: Michael
authors.initials: M
authors.lastname: Mangan
authors.affiliation: Research School of Biology, The Australian National University, 46 Sullivans Creek Road, Canberra ACT 2601, Australia.
authors.forename: Jochen
authors.initials: J
authors.lastname: Zeil
authors.affiliation: School of Informatics, University of Edinburgh, 10 Crichton Street, Edinburgh EH8 9AB, UK.
authors.forename: Barbara
authors.initials: B
authors.lastname: Webb
authors.affiliation: School of Informatics, University of Edinburgh, 10 Crichton Street, Edinburgh EH8 9AB, UK; Centre de Recherches sur la Cognition Animale, CNRS, Université Paul Sabatier, 118 route de Narbonne, 31062 Toulouse, France. Electronic address: antoine.wystrach@univ-tlse3.fr.
authors.forename: Antoine
authors.initials: A
authors.lastname: Wystrach
mesh_terms: D000818:Animals; D001000:Ants / Q000502:physiology*; D003463:Cues; D006702:Homing Behavior / Q000502:physiology*; D008568:Memory; D009949:Orientation / Q000502:physiology; D013028:Space Perception; D065854:Spatial Navigation; D014785:Vision, Ocular / Q000502:physiology
keywords: ants; backward motion; celestial compass; directional frame of reference; egocentric memories; holonomic; insects; landmarks; navigation