How do red wood ants orient during diurnal and nocturnal foraging in a three dimensional system? II. Field experiments

Abstract

In order to investigate the orientational mechanisms involved in the ants' three dimensional movements workers of the red wood antFormica nigricans were enticed to forrage, both during the day and in night, in an artifical tree set up in their natural environment. Celestial cues were found to be irrelevant in the ants' directionnality. In contrast, the results stress the importance of terrestrial and chemical landmarks both in the orientation on the vertical axis and on the horizontal plane. When a discrepancy was experimentally induced in the directional information provided by the two types of landmarks, terrestrial cues were preferred over the chemical ones. In addition, kinaesthetic information is used as a back-up orientating system at the cross-road. On the other hand, nocturnal orientation was found to be essentially based on chemical cues. These results support therefore the assumption of a simultaneous utilization of all the available directional information apart from alternative use of single cues during competitive situations and rule out the concept of an absolute hierarchie of cues.