An experimental study of the foraging strategy of the wood ant Formica aquilonia

Abstract Individual foragers return to a site at which food has been discovered. This site allegiance is maintained provided that the food source is maintained. If it is not, a random search precedes discovery of an alternative source to which allegiance is transferred. Particular sites are located initially by the use of visual cues. However, such cues have a diminishing importance for orientation since, as the route becomes familiar, a spatial map is constructed from bearings of, and distances between, the major topographical features. Since ants individually learn the most economical route, this ability, together with site allegiance, results in the observed route fidelity. The foraging population established is variable and is related to the previous availability of food and consequent need of the colony. Environmental factors affect the amount of food collected and influence the size of the foraging population through the hunger of the colony. A variable colonial foraging response is dependent upon the tendency of individual nest-bound ants to forage when stimulated by an aroused replete ant returning from a successful foray. The availability of food, but apparently not its position, is communicated: recruited ants forage to remembered sites at which they have been rewarded.