Foraging ecology of the Australian desert ant Melophorus bagoti

Melophorus bagoti is a solitary foraging desert ant of Central Australia. As part of a major endeavour to study insect navigation it has recently attracted considerable attention, calling for an intimate knowledge of its foraging ecology. This thesis examines foraging traits on the colony level, and investigates the strategies that are used by foragers when searching for resources. Foraging activity is limited to a window of ca. 50-70°C soil surface temperature, when foragers scavenge opportunistically for food items. Although seemingly capable of laying chemical trails when moving the colony, recruitment behaviour towards large food sources appears to work without the use of pheromone trails. When unable to locate a single target, like a food source or the nest entrance, foragers engage in a systematic search. The size of their search paths is flexible, which allows them to increase search efficiency. To this end, several different cues are used, which inform the foragers of the whereabouts of the target. In food searches, size depends on the type of food, and matches the natural distribution pattern of food items. In nest searches, size depends on the accuracy of the path integrator, which is a navigational tool that accumulates errors. In addition, it depends on the presence of visual navigation cues in the surrounding panorama, and on the amount of information that can be derived from these visual cues. Interestingly, presence or absence of visual cues also changes the movement pattern of searching foragers. Taken together, these results demonstrate how closely searching behaviour is linked with a forager's navigational toolkit, and with its environment.