Abstract
A wide range of group-living animals construct tangible infrastructure networks, often of remarkable size and complexity. In ant colonies, infrastructure construction may require tens of thousands of work hours distributed among many thousand individuals. What are the individual behaviours involved in the construction and what level of complexity in inter-individual interaction is required to organize this effort? We investigate this question in one of the most sophisticated trail builders in the animal world: the leafcutter ants, which remove leaf litter, cut through overhangs and shift soil to level the path of trail networks that may cumulatively extend for kilometres. Based on obstruction experiments in the field and the laboratory, we identify and quantify different individual trail clearing behaviours. Via a computational model, we further investigate the presence of recruitment, which-through direct or indirect information transfer between individuals-is one of the main organizing mechanisms of many collective behaviours in ants. We show that large-scale transport networks can emerge purely from the stochastic process of workers encountering obstructions and subsequently engaging in removal behaviour with a fixed probability. In addition to such incidental removal, we describe a dedicated clearing behaviour in which workers remove additional obstructions independent of chance encounters. We show that to explain the dynamics observed in the experiments, no information exchange (e.g. via recruitment) is required, and propose that large-scale infrastructure construction of this type can be achieved without coordination between individuals.
Highlights
The construction and use of paths and highways is not a unique feature of humans, but is known across many different animals including elephants [1], domesticated cattle [2], voles [3], quokkas [4], marine snails [5] and many ants [6]
We investigated two mechanistic questions: (i) are there different individual-level trail clearing behaviours? and (ii) does recruitment play a role in organizing trail construction? To study these questions, we placed normalized obstructions on foraging trails, observed the individual and colony-level removal dynamics and constructed a computational model based on the observed behavioural rates
We focused on the investigation of recruitment dynamics in a natural environment only
Summary
The construction and use of paths and highways is not a unique feature of humans, but is known across many different animals including elephants [1], domesticated cattle [2], voles [3], quokkas [4], marine snails [5] and many ants [6]. We placed normalized obstructions on foraging trails, observed the individual and colony-level removal dynamics and constructed a computational model based on the observed behavioural rates.
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