Modelling the Effects of Colony Age on the Foraging Behaviour of Harvester Ants

The colonies of certain species of ants, for example Pogonomyrmex barbatus, exhibit changes in behaviour as the colonies grow older, despite nearly all of the individual ants being replaced each year [1]. The behaviour of older colonies is more stable, and they are more likely to avoid intraspecific conflict [2]. Gordon hypothesised that the reason for this is that a 3-4 year old colony is in the steepest part of its growth curve, i.e. the 4000 workers of the 3 year-old colony are feeding 6000 larvae, and that the aggression of individual ants is based on colony level food requirements. This study aims to model this phenomenon using an individual-based simulation. The results from model are compared with field experiments taken over a period of years at the study site in New Mexico [3, 4]. The model provides support to the biological hypothesis by showing that both colony age and aggression of individual ants have significant effects on foraging ranges.