The View from the Trees: Nocturnal Bull Ants, Myrmecia midas, Use the Surrounding Panorama While Descending from Trees.

Cody A Freas,Ken Cheng,Ajay Narendra,Antione Wystrach

doi:10.3389/fpsyg.2018.00016

Abstract

Solitary foraging ants commonly use visual cues from their environment for navigation. Foragers are known to store visual scenes from the surrounding panorama for later guidance to known resources and to return successfully back to the nest. Several ant species travel not only on the ground, but also climb trees to locate resources. The navigational information that guides animals back home during their descent, while their body is perpendicular to the ground, is largely unknown. Here, we investigate in a nocturnal ant, Myrmecia midas, whether foragers travelling down a tree use visual information to return home. These ants establish nests at the base of a tree on which they forage and in addition, they also forage on nearby trees. We collected foragers and placed them on the trunk of the nest tree or a foraging tree in multiple compass directions. Regardless of the displacement location, upon release ants immediately moved to the side of the trunk facing the nest during their descent. When ants were released on non-foraging trees near the nest, displaced foragers again travelled around the tree to the side facing the nest. All the displaced foragers reached the correct side of the tree well before reaching the ground. However, when the terrestrial cues around the tree were blocked, foragers were unable to orient correctly, suggesting that the surrounding panorama is critical to successful orientation on the tree. Through analysis of panoramic pictures, we show that views acquired at the base of the foraging tree nest can provide reliable nest-ward orientation up to 1.75 m above the ground. We discuss, how animals descending from trees compare their current scene to a memorised scene and report on the similarities in visually guided behaviour while navigating on the ground and descending from trees.

Highlights

Solitary ant foragers moving on the ground are adept at navigating through their environment, both while searching for resources and when returning to their nest
Landmark based navigation has been widely studied in diurnal ants (Wehner et al, 1996; Fukushi, 2001; Wehner, 2003; Cheng et al, 2009; Collett, 2010; Bühlmann et al, 2011; Wystrach et al, 2011a,b, 2012; Lent et al, 2013; Narendra et al, 2013; Schultheiss et al, 2016; Freas and Cheng, 2017; Freas et al, 2017c), and the current knowledge of landmark use in ants that forage nocturnally is expanding (Reid et al, 2011; Warrant and Dacke, 2011; Freas et al, 2017a,b; Narendra and Ramirez-Esquivel, 2017; Narendra et al, 2017)
We show that M. midas foragers successfully orient to the nest side of their foraging tree during their descent

Summary

Introduction

Solitary ant foragers moving on the ground are adept at navigating through their environment, both while searching for resources and when returning to their nest. Landmark based navigation has been widely studied in diurnal ants (Wehner et al, 1996; Fukushi, 2001; Wehner, 2003; Cheng et al, 2009; Collett, 2010; Bühlmann et al, 2011; Wystrach et al, 2011a,b, 2012; Lent et al, 2013; Narendra et al, 2013; Schultheiss et al, 2016; Freas and Cheng, 2017; Freas et al, 2017c), and the current knowledge of landmark use in ants that forage nocturnally is expanding (Reid et al, 2011; Warrant and Dacke, 2011; Freas et al, 2017a,b; Narendra and Ramirez-Esquivel, 2017; Narendra et al, 2017) What these studies have in common is that they explore navigational behavior that occurs in two dimensions while ants are travelling to goal locations on the ground. Nocturnal species of this genus have the added challenge of completing this feat during the evening and morning twilight when visual cues are less salient compared to those used by diurnal species (Reid et al, 2011, 2013; Freas et al, 2017a,b; Narendra et al, 2017)

Results

Discussion

Conclusion