Polydomy

Polydomy is a nesting strategy whereas an ant colony occupies two or more spatially separated nests. This contrasts with monodomy, where a colony occupies a single nest structure. There are many ant species that exhibit polydomy and so its expression varies greatly, as does the potential functions and ecology drivers of why species may evolve to have single versus multiple nests.

Wood Ants
A group of northern temperate forest dwelling Formica species that form large complexes of nest mounds. Details of their nesting behavior have likely been studied across more decades and been the subject of more nesting studies than any other group of ants.

Individual nests can be quite active and regularly send out foragers to collect honeydew from arboreal aphid colonies. Others nests do not forage. The role of these non-foraging nests was the subject of a study by Ellis and Robinson (2015:) Abstract - A colony of red wood ants can inhabit more than one spatially separated nest, in a strategy called polydomy. Some nests within these polydomous colonies have no foraging trails to aphid colonies in the canopy. In this study we identify and investigate the possible roles of non-foraging nests in polydomous colonies of the wood ant Formica lugubris. To investigate the role of non-foraging nests we: (i) monitored colonies for three years; (ii) observed the resources being transported between non-foraging nests and the rest of the colony; (iii) measured the amount of extra-nest activity around non-foraging and foraging nests. We used these datasets to investigate the extent to which non-foraging nests within polydomous colonies are acting as: part of the colony expansion process; hunting and scavenging specialists; brood-development specialists; seasonal foragers; or a selfish strategy exploiting the foraging effort of the rest of the colony. We found that, rather than having a specialised role, non-foraging nests are part of the process of colony expansion. Polydomous colonies expand by founding new nests in the area surrounding the existing nests. Nests founded near food begin foraging and become part of the colony; other nests are not founded near food sources and do not initially forage. Some of these non-foraging nests eventually begin foraging; others do not and are abandoned. This is a method of colony growth not available to colonies inhabiting a single nest, and may be an important advantage of the polydomous nesting strategy, allowing the colony to expand into profitable areas.