Route Learning and Transport of Resources during Colony Relocation in Australian Desert Ants

Abstract

Many ant species are able to respond to dramatic changes in local conditions by relocating the entire colony to a new location. While we know that careful learning walks enables the homing behavior of foraging ants to their original nest, we do not know whether additional learning is required to navigate to the new nest location. To answer this question, we investigated the nest relocation behavior of a colony of Australian desert ants Melophorus bagoti that relocated their nest in response to heavy rainfall in the semi-desert terrain of Alice Springs. We identified five types of behavior: exploration between nests (Old-to-New nest and New-to-Old nest), transport from Old to New nest, and re-learning walks at Old and New nests. Initially, the workers performed relearning walks at the Old nest and exploratory walks between the Old and New nests. Once they completed the exploratory walks, the workers transported resources and brood to the new nest. Finally, we observed the workers performing relearning walks at the New nest. While the relearning walks at the Old nest were slow and appear to enable exploratory walks to the New nest, the relearning walks at the new nest were faster and appeared to enable homing from foraging trips. These observations shed insight on how learning helps these ants to respond to sudden changes in their environment. Statement of significanceIn this study, we examined one nest of red honey ants, Melophorus bagoti, in Central Australia relocating their nest after a spell of heavy rainfall, which, we presumed, damaged the nest that the colony was living in. After the new nest some 20 m away was mostly dug, we examined the behaviors that orchestrated the move. Workers did a bit of learning of the route to the new nest before transporting any resources. They executed short loops around the old nest, mostly aimed in the direction of the new nest, known as relearning walks. Then they walked back and forth between the old and new nests without carrying any resources, a process we called exploration walks. Then the workers undertook the laborious process of moving house, that is, transporting workers unfamiliar with the route, larvae, and pupae to the new nest. After this stage, we observed ants doing more relearning walks at the new nest in preparation for foraging from their new home. These relearning walks covered all directions around the nest. Our study showed for the first time the importance of the process of learning in nest relocation, a key response to extreme environmental challenges, broadening the role of learning in the lives of these social insects.