title: Nest excavation in ants: group size effects on the size and structure of tunneling networks.
abstract: Collective digging activity was studied in the ant Messor sancta Forel in laboratory conditions and with a two dimensional set-up. We analyzed the digging dynamics and topology of tunneling networks excavated by groups of workers ranging from 50 to 200 individuals over 3 days. In all conditions, the dynamics of excavated sand volume were clearly non-linear. Excavation began with an exponential growth and after 3 days reached a saturation phase in which activity was almost totally stopped. The final volume of sand excavated was positively correlated with the number of workers. At the end of the experiments, the two-dimensional tunneling networks were mapped onto planar graphs where the vertices represent small chambers or intersections between tunnels and the edges represent tunnels. We found that all the networks belonged to a same topological family and exhibited several striking invariants such as the distribution of vertex degree that follows a power law. When increasing the number of ants, some changes occurred in the network structure, mainly an increase in the number of edges and vertices, and the progressive emergence of enlarged and highly connected vertices.
authors.affiliation: Centre de Recherches sur la Cognition Animale, CNRS-UMR 5169, Université Paul Sabatier, 118 route de Narbonne, 31062, Toulouse Cedex 4, France. camille.buhl@adelaide.edu.au
authors.forename: Camille
authors.initials: C
authors.lastname: Buhl
authors.forename: Jacques
authors.initials: J
authors.lastname: Gautrais
authors.forename: Jean-Louis
authors.initials: JL
authors.lastname: Deneubourg
authors.forename: Guy
authors.initials: G
authors.lastname: Theraulaz
mesh_terms: D000818:Animals; D001000:Ants / Q000502:physiology*; D005602:France; D011156:Population Density; D012919:Social Behavior