Antony S. Aleksiev1, Ana B. Sendova-Franks2, and Nigel R. Franks1. (1) School of Biological Sciences, University of Bristol, Woodland Road, Bristol, BS8 1UG, United Kingdom, (2) School of Mathematical Sciences, University of the West of England, Bristol, Frenchay Campus, Coldharbour Lane, Bristol, BS16 1QY, United Kingdom
The ant Temnothorax albipennis builds some of the simplest nests found among social insects. Colonies live in rock crevices and merely encircle themselves with a dry-stone wall. Yet, their nests have some sophisticated properties. When colonies grow, building is explosive and episodic. Our work focuses on foraging for building material. Unlike ants that build by excavation, T. albipennis colonies have to collect building materials from outside the nest. We examined their preferences for building materials by presenting colonies with a choice of large and small sand grains at different distances from the nest. It is clear that, in terms of volumetric benefits and temporal costs, the large sand grains are always more profitable. Nevertheless, the ants always collect small grains albeit in diminishing proportions with distance. Thus, they show partial preferences. We examined the possibility that dry-stone walls composed of two grain sizes might be better, in terms of stability or compactness, than walls composed of a single grain size. Our experiments suggest that this is likely. However, partial preferences are usually interpreted as foraging errors rather than a beneficial strategy. Partial preferences are frequently seen in other cases of foraging and occur most often when “mistakes” are not very costly. The mistakes may also be related to social foraging and the division of labour. Solitary builders get lots of practice. By contrast, social builders can compete for work and the opportunity to perfect their skills or choices. Close to the nest, many “amateurs” may make few trips for construction materials and complete the wall quickly. Away from the nest, many fewer foraging “professionals” might each make many trips and thus perfect their choices. We are currently investigating these issues that link building behaviour, foraging, learning and the division of labour.