The life history of harvester ant colonies.

A long-term study of a population of desert seed-eating ant colonies of the red harvester ant, Pogonomyrmex barbatus, in New Mexico, USA, shows that a colony can live for 20-30 years-the lifespan of its founding queen. A colony's collective behaviour shifts in the course of its life history. These changes, generated by social interactions within the colony, adjust the behaviour of the colony as it grows older and larger, in response to its environment and neighbouring colonies. A worker lives only a year and performs different tasks as it ages, in response to interactions with other workers and the local surroundings. A colony's behaviour changes-becoming more stable and consistent-as the colony grows older, with more ants to participate in social interactions. A neighbourhood of colonies, often of similar age, grows old together. Colonies differ in how they regulate foraging behaviour collectively to manage water loss. These differences influence how foragers of neighbouring colonies partition foraging area. In a harsh but stable environment, the gradual behavioural shifts over a colony's lifespan allow it to adjust to slow changes in the composition of its neighbourhood and in environmental conditions.This article is part of the discussion meeting issue 'Understanding age and society using natural populations'.