Optimal construction of army ant living bridges

Abstract

Integrating the costs and benefits of collective behaviors is a fundamental challenge to understanding the evolution of group living. These costs and benefits can rarely be quantified simultaneously due to the complexity of the interactions within the group, or even compared to each other because of the absence of common metrics between them. The construction of 'living bridges' by New World army ants -which they use to shorten their foraging trails -is a unique example of a collective behavior where costs and benefits have been experimentally measured and related to each other. As a result, it is possible to make quantitative predictions about when and how the behavior will be observed. In this paper, we extend a previous mathematical model of these costs and benefits into a general framework for analyzing the optimal formation, and final configuration, of army ant living bridges. We provide experimentally testable predictions of the final bridge position, as well as the optimal formation process for certain cases, for a wide range of scenarios, which more closely resemble common terrain obstacles that ants encounter in nature. As such, our framework offers a rare benchmark for determining the evolutionary pressures governing the evolution of a naturally occurring collective animal behavior.

Social insects and beyond: The physics of soft, dense invertebrate aggregations

“…Aggregations can also travel to more favorable environments by walking or crawling, such as the processions of larvae (Brues, 1951; Lashley et al, 2018; White and Deacon, 2020). Finally, an aggregation made up of a small fraction of a colony can help the entire colony travel over rough terrain, such as marching army ants that link their bodies into bridges across gaps to shorten the path of the other ants (Graham et al, 2017; Reid et al, 2015).…”

“…For example, when raiding, Eciton army ants come across a gap in their path, a fraction of them self-organize into a bridge (Figure 6(b) and Supplemental Video S2). The bridge becomes shorter or longer depending on the flow of ants over it, optimizing the number of raiding ants and bridge ants to maximize their foraging rate (Graham et al, 2017; Reid et al, 2015; Rettenmeyer et al, 2011).…”

Demonstration of cooperative obstacle crossing by sensorless swarm robots based on the mechanical interaction aided field control

“…In the traditional approach, each robot senses the field and exchanges information between robots to perform cooperative actions; in our proposed approach, the field is modified dynamically by a robot to interact with another one. (Gauci et al, 2014) 3 (Cucu et al, 2015) (Pinciroli et al, 2013) 3 (Murata et al, 2002) ( Mataric et al, 1995) ( Hirose et al, 1996) (Brown et al, 2002) (Casarez and Fearing, 2016)( 2019) ( 1997) (Butler et al, 2001) (Suzuki et al, 2009) ( 1(a)) (Graham et al, 2017) Revzen et al, 2011) (Napp et al, 2012) (Fujisawa et al, 2015) (Sugawara et al,2018)…”