Ant Navigation

Ants, and in particular Cataglyphis bicolor and Cataglyphis fortis, are a model organism for the study of animal navigation. The results of this body of work provide a remarkable accounting of how ants, and animals in general, can track and monitor their movement in ways that allow for sophisticated decision making. Rüdiger Wehner has been at the center of much of this Cataglyphis research. Wehner and his colleagues have been conducting seasonal fieldwork studying C. bicolor and C. fortis in the area of Mahrès, Tunisia for 50 years (Wehner 2019). The book Desert Navigator: The Journey of an Ant (Wehner 2020) provides a fascinating summary of how this work was accomplished and its many important findings.

These studies have examined a range of physiological and behavioral features of ants to understand how perception of the environment and decision making come together to determine where individuals decide to move.

Species Studied

 * Cataglyphis bicolor
 * Cataglyphis fortis
 * Veromessor pergandei

Visual Systems
Several different kinds of insects are able to detect polarized light patterns in the sky. Ants that use polarized light for navigation have specialized UV receptors in the dorsal-most portion of their ommatidia, i.e., the dorsal rim area. These contains modified rhabdoms that are atypical for most ants.

Polarized Light
Freas et al. (2019) - One visual cue known to be used to obtain directional information in insects is the polarised light pattern in the overhead sky (Wehner 1989; Wehner and Labhart 2006; Greiner et al. 2007; Reid et al. 2011; Lebhardt et al. 2012; Lebhardt and Ronacher 2013; Zeil et al. 2014; Warrant and Dacke 2016; Freas et al. 2017a, 2018a; Palavalli-Nettimi and Narendra 2018), which insects detect through specialised regions in their eyes called the dorsal rim areas (Labhart and Meyer 1999; Labhart et al. 1992; Homberg and Paech 2002). Polarised light naturally occurs as the product of light scattering as it enters the atmosphere. This results in the formation of a polarised light pattern arranged in concentric circles originating from the sun’s (or moon’s) position in the sky (Fent 1986; Wehner 1994). As the sun or moon nears the horizon, the polarisation pattern in the overhead sky strengthens and simplifies with the angle of polarisation positioned perpendicular to the azimuth angle of the sun/moon (Foster et al. 2018a). This angle of polarisation remains stable in the overhead sky even if the sun/moon is obscured or during twilight, when the sun descends below the skyline (Rozenberg 1966), making it a useful directional cue for orienting insects (Dacke et al. 2003; Wehner and Müller 2006; Warrant and Dacke 2016; Foster et al. 2018a, b).