Scaling of ant colony interaction networks

Abstract

In social insect colonies, individuals are physically independent but functionally integrated by interaction networks which provide a foundation for communication and drive the emergence of collective behaviors, including nest architecture, division of labor, and potentially also the social regulation of metabolic rates. To investigate the relationship between interactions, metabolism, and colony size, we varied group size for harvester ant colonies (Pogonomyrmex californicus) and assessed their communication networks based on direct antennal contacts and compared these results with proximity networks and a random movement simulation. We found support for the hypothesis of social regulation; individuals did not interact with each other randomly but exhibited restraint. Connectivity scaled hypometrically with colony size, per-capita interaction rate was scale-invariant, and smaller colonies exhibited higher measures of closeness centrality and edge density, correlating with higher per-capita metabolic rates. Although the immediate energetic cost for two ants to interact is insignificant, the downstream effects of receiving and integrating social information can have metabolic consequences. Our results indicate that individuals in larger colonies are relatively more insulated from each other, a factor that may reduce or filter noisy stimuli and contribute to the hypometric scaling of their metabolic rates, and perhaps more generally, the evolution of larger colony sizes.

Reverse social contagion as a mechanism for regulating mass behaviors in highly integrated social systems

“…We analyze experimental data of harvester ant colonies ( Pogonomyrmex californicus ) by Waters et al ( 19 ) and partially re-analyzed by Toth et al ( 23 ), combining simultaneous measurements of whole-colony metabolic rates via flow-through respirometry and video recordings of ants within their artificial nest enclosures (Fig. 2 a).…”

“…Video observations were conducted in colony nest enclosures (one 30-second uncompressed AVI video per colony at a spatial resolution of pixels and time resolution of 15 frames per second). These videos were manually tracked to score locomotory patterns of workers, and some of them were later examined by Toth et al ( 23 ) to investigate interactions among workers. Here, we examine the whole set of 16 videos, refining and verifying those studied by Toth et al ( 23 ) and completing the analysis of the remaining ones.…”

“…These videos were manually tracked to score locomotory patterns of workers, and some of them were later examined by Toth et al ( 23 ) to investigate interactions among workers. Here, we examine the whole set of 16 videos, refining and verifying those studied by Toth et al ( 23 ) and completing the analysis of the remaining ones. In particular, for each video, we manually recorded the positions of each visually trackable worker (85% of the total number of counted workers ( 19 ), averaged over the colonies) to preserve their identity.…”

Examining the Social Behavior of Ant Colonies Using Complex Networks

“…Complex Network Theory is one such framework that provides a wide range of tools to extract properties about the system modeled as a complex network. By modeling the colony's system as a network, where ants are nodes and their interactions are edges, it can be explicitly analyzed the interactions a given ant or group of ants have, defining statements about their social or individual behavior [24].…”