Ant-inspired navigation in unknown environments

Abstract

In contrast to most other ant species, desert ants (Cataglyphis fortis) do not use pheromones to mark their path. When returning from a foraging trip to their nest they navigate both by path integration and by visual landmarks. An egocentric navigation system based on path integration alone su ers from two major pitfalls: 1. It must run uninterrupted as long as the animal moves and 2. It is inherently susceptible to cumulative navigation errors. Hence, if the animal visited an area repeatedly, it is advantageous to take an occasional positional x by acquiring landmark-based geocentered (alocentric) information. Indeed desert ants and honeybees use such information in addition to path integration. On a familiar route, when ants can steer by visual landmarks, they adopt a xed and often circuitous path consisting of several separate segments that point in di erent directions. Such multi-segment journeys are composed partly of stored local movement vectors, which are associated with landmarks and are recalled at the appropriate place. During the experiments reported in [4] and [1], ants collected right before entering their nest after a foraging trip are deprived of their global vector. When these ants were placed at points along their familiar route, they were able to use previously seen visual features in order to return to their nest. It is believed [1], that two dimensional visual snapshots of landmarks along the homing path are stored in the memory of the ants and upon recognition they trigger a local vector that describes the transition to the next landmark on the way to the nest. These local vectors are also calculated based on odometry. They are links that point towards the direction of the next landmark along the path and are proportional to the distance between consecutive locations. Due to their limited length compared to the global vector the local transitions are more precisely learned and reproduced during foraging trips. The vision-based (local) navigation in ants works in parallel with global navigation. In order to ensure that an alternative navigation mechanism is available, desert ants use landmark-based navigation as the main method along familiar paths. They resort to global navigation only if the former fails, that is if in a dynamic environment landmarks are missing or are being occluded by new ones. If one of