Annual patterns of forager allocation in the Florida harvester ant (Pogonomyrmex badius)

An ant colony is a self organizing system that allocates individuals to competing internal functions such as brood care, foraging and nest construction. Though largely untested, the ratios of individuals attending to these tasks must change in order to optimize colony efficiency during each annual cycle. For two years, forager population size was estimated for the Florida harvester ant (Pogonomyrmex badius) using the Lincoln index mark-recapture method. Each estimate was followed by the immediate excavation and census of the colony, thereby allowing calculation of the proportion of the colony that foraged. This proportion gradually increased from zero in early spring, peaking at 40% in late May and then declining to zero in early November. While allocation to foraging was strongly related to season and brood, it was not related to colony size or colony reproductive maturity. Additionally, repeated monthly estimates of forager population size and turnover rate were made for a set of colonies throughout the annual cycle. Concurrent forager removal experiments revealed the relationship between forager allocation, worker age and colony demand, suggesting a mechanism that could generate the observed patterns of allocation.