Faster up a tree: enigma of cooperative transport in tropical weaver ants

Cooperative transport is a natural behaviour that is documented rarely in the animal kingdom. Other than humans, ants are presumably the only group of animals who employ such behaviour, enabling them to transport large objects that individuals cannot carry themselves. It is challenging to understand how ants interact with each other in such a dynamic process that needs a coordinated effort. Previous studies have focused on horizontal transport and transport across marginal inclines, however cooperative transport across vertical terrain has not been analysed. In the present study, we investigate the transport velocity, speed and path straightness across horizontal and vertical transport in a tropical arboreal ant species in its natural habitat. Further we investigate the transport parameters at group and individual levels to comprehend the temporal and spatial dynamics of such a decentralised process. Through individual level tracking, we could document the speed of unencumbered ants on level ground as well as while climbing a tree. Our results showcase that Oecophylla smaragdina ants may have evolved to an arboreal life in the tropics and exhibit enhanced efficiency for vertical transports as compared to horizontal transports. This exceptional efficiency is presumably a result of their climbing ability as well as gravity induced coordination. Future studies targeted at addressing these questions would help us reveal why these tropical ants are better at climbing trees than running on the ground.