Surface curvature guides early construction activity in mound-building termites

Abstract

Termite colonies construct towering, complex mounds, in a classic example of distributed agents coordinating their activity via interaction with a shared environment. The traditional explanation for how this coordination occurs focuses on the idea of a "cement pheromone", a chemical signal left with deposited soil that triggers further deposition. Recent research has called this idea into question, pointing to a more complicated behavioral response to cues perceived with multiple senses. In this work, we explored the role of topological cues in affecting early construction activity in Macrotermes. We created artificial surfaces with a known range of curvatures, coated them with nest soil, placed groups of major workers on them, and evaluated soil displacement as a function of location at the end of one hour. Each point on the surface has a given curvature, inclination, and absolute height; to disambiguate these factors, we conducted experiments with the surface in different orientations.Soil displacement activity is consistently correlated with surface curvature, and not with inclination nor height. Early exploration activity is also correlated with curvature, to a lesser degree. Topographical cues provide a long-term physical memory of building activity in a manner that ephemeral pheromone labeling cannot. Elucidating the roles of these and other cues for group coordination may help provide organizing principles for swarm robotics and other artificial systems.

A growth model driven by curvature reproduces geometric features of arboreal termite nests

“…By identifying local surface curvature as the only triggering stimulus of termite construction, our model certainly ignores a large part of the complexity of behaviour of termites, and it does not include the possible effects of direct termite interactions, such as traffic and crowding at the building site. Yet, the identification of curvature as an important stigmergic stimulus that can guide termite building activity is well supported in the scientific literature [ 13 , 15 , 16 ], and our model is sufficient to reproduce some key features of arboreal Nasutitermes nests: the intricate structure, the existence of a typical length scale, the sensitivity to boundary and initial conditions and the abundance of saddle-shaped structures of zero mean curvature. On these grounds, we can conclude that, while real termite behaviour could be more complex, a response to curvature alone is in itself sufficient to explain a large part of the complexity observed in arboreal termite nests.…”

Liquid brains, solid brains

“…Mobility is shown to increase information flow among moving agents, which encounter and communicate with new agents over time. Calovi et al [44] show that liquid systems, in this case termites, use the physical structure of the surrounding environment as an essential component of computation. Kao et al [45] describe a different sort of hybrid system in which the modular structure of moving animal populations implies that some communication is more persistent and local (as in a solid royalsocietypublishing.org/journal/rstb Phil.…”

Potential of termite mounds and its surrounding soils as soil amendments in smallholder farms in central Uganda

“…Out of the estimated total number of 2600 described species of termites, few have been considered as a major pest of food crops such as cereals, roots, tubers, legumes and fruit trees [3][4][5][6]. Despite being considered as pests, termites are biological indicators of soil fertility and ecosystem engineers [7][8][9][10][11]. Termite's activities such as collection and transportation of living and dead plants, animal materials, soil particles, and burrowing lead to the improvement of soil physicochemical properties and microbial population and diversity of the termite mound and their surrounding soils [12][13][14][15][16][17].…”