Path integration in a three-dimensional world: the case of desert ants

Abstract

Desert ants use path integration to return from foraging excursions on a shortcut way to their nests. Intriguingly, when walking over hills, the ants incorporate the ground distance, the paths' projection to the horizontal plane, into their path integrator. This review discusses how Cataglyphis may solve this computational feat. To infer ground distance, ants must incorporate the inclination of path segments into the assessment of distance. Hair fields between various joints have been eliminated as likely sensors for slope measurement, without affecting slope detection; nor do postural adaptations or changes in gait provide the relevant information. Changes in the sky's polarization pattern due to different head inclinations on slopes were ruled out as cues. Thus, the mechanisms by which ants may measure slopes still await clarification. Remarkably, the precision of slope measurement is roughly constant up to a 45° inclination, but breaks down at 60°. An encounter of sloped path segments during a foraging trip induces a general acceptance of slopes, however, slopes are not associated with specific values of the home vector. All current evidence suggests that Cataglyphis does not compute a vector in 3-D: path integration seems to operate exclusively in the horizontal plane.

Neuronal Coherence Agent for Shared Intentionality: A Hypothesis of Neurobiological Processes Occurring during Social Interaction

“…Darwin noted a navigation system in animals -the Path Integration (PI). Individual ants perform large distance foraging excursions of up to 1200 m, and while returning, the ants select a direct shorter path back to their nests and are capable of inferring this ground distance when walking over hills [23]. These organisms determine the actual navigation strategy from complemented and contrasted navigation mechanisms with different weights that are based on their reliability.…”

Johnston's organ and its central projections in Cataglyphis desert ants

“…Cataglyphis measures the walked distance during foraging trips via a step integrator (Wittlinger, Wehner, & Wolf, 2006). However, to estimate the correct distance from the nest, Cataglyphis has to take the slopes on its way into account and integrate this information into its path integrator (Grah & Ronacher, 2008; Grah, Wehner, & Ronacher, 2005; Ronacher, 2020). In contrast to other ants (Markl, 1962; Markl, 1963), bristle fields on the ants' body do not seem to be involved in the reception of gravitational forces in Cataglyphis (Wittlinger, Wolf, & Wehner, 2007).…”

“…In contrast to other ants (Markl, 1962; Markl, 1963), bristle fields on the ants' body do not seem to be involved in the reception of gravitational forces in Cataglyphis (Wittlinger, Wolf, & Wehner, 2007). Up to now, the mechanism by which Cataglyphis measures slopes still remains elusive (Ronacher, 2020). The JO is a promising candidate to fulfill this function in gravity reception.…”

“…Cataglyphis (Wittlinger, Wolf, & Wehner, 2007). Up to now, the mechanism by which Cataglyphis measures slopes still remains elusive (Ronacher, 2020). The JO is a promising candidate to fulfill this function in gravity reception.…”

“…However, for several navigational components the location of the sensory organ is still unknown or remained speculative: During early learning walks, Cataglyphis nodus uses the earth's magnetic field as a compass (Fleischmann, Grob, Müller, Wehner, & Rössler, 2018). Later, during foraging, Cataglyphis ants use gravitational information to account for slopes during path integration along uneven terrain (Ronacher, 2020; Wohlgemuth, Ronacher, & Wehner, 2001). To finally pinpoint food sources on their extensive foraging trips or the nest entrance in the final approach during homing, Cataglyphis fortis also utilizes a wind compass (Steck, Hansson, & Knaden, 2009; Wolf & Wehner, 2000).…”