Meeting Abstract
83.4 Monday, Jan. 6 11:15 Ant traffic and communication in confined environments GRAVISH, N.*; GOLD, G.E.; ZANGWILL, A.D.; GOODISMAN, M.A.D.; GOLDMAN, D.I.; Harvard University; Georgia Tech; Georgia Tech; Georgia Tech; Georgia Tech gravish@seas.harvard.edu
Many social insects construct subterranean nests which provide a safe location for rearing the young. However, nests can be confining; this can limit effective transportation of both resources and information. Moreover, in ant colonies the mechanistic nature of inter-ant communication places physical limits on the mobility of workers in subterranean nests. Thus collective mobility and communication in subterranean nests are at odds: the physical interactions necessary for information and resource exchange create obstacles that impede traffic flow and reduce worker mobility. To understand the effect of confinement on ant mobility and communication, we monitored the traffic of fire ant (Solenopsis invicta) workers in laboratory tunnels of diameter D = 2 – 6 mm. We observed the traffic of 5 groups of workers drawn from 3 colonies. We observed that regions of high ant density were correlated with a decrease in ant speed in all tunnels. The occurrence of high-density regions in a tunnel often coincided with bouts of tactile interaction using antennae (called antennation). The duration of antennation, T, was linearly proportional to the number of ants in the group, N. The slope of T versus N increased as D decreased indicating that smaller tunnels were more prone to formation of traffic jams. To elucidate the contributions of behavior and geometry on foraging traffic we developed a model, which incorporated the minimal features of ant tunnel traffic—physical interactions and confinement, with one free parameter—the duration of antennation. We found that the model reproduced the traffic patterns observed in experiment. Our experimental and simulation results indicate that traffic jams may be mitigated in foraging tunnels both by alteration of tunnel geometry and modulation of ant behavior. We compare these predictions with observations from natural fire ant tunnels.
