Collective contests

The primary enemy of ants are other ants, often of the same species: ants are not only competitors for rare nest sites in species that do not build their own nests, but also fight over brood (which is a valuable resource); and ant colonies often completely eliminate other colonies. It is thus likely that strategies for assessing and defending against other ant colonies are as sophisticated as those for, for example, collective foraging. Here we show that defensive resources are adaptively allocated across colony space, and that colonies, probably using interaction rates and assessment of worker speed and aggression, can determine the fighting ability and resources held by other colonies to determine their contest behavior.

Defense allocation

Donaldson-Matasci MC, Powell S, Dornhaus A 2022, ‘Distributing defenses: How resource defendability shapes the optimal response to risk’, The American Naturalist 199: 636-652 - pdf - a general mathematical model to determine the optimal strategy for dividing defenses among assets depending on their value, defendability, and risk of attack; shows that if some assets have little chance of being defended, it is better to give up and not invest in their defense at all

Powell S, Donaldson-Matasci M, Woodrow-Tomizuka A, Dornhaus A 2017 ‘Context-dependent defences in turtle ants: Resource defensibility and threat level induce dynamic shifts in soldier deployment’, Functional Ecology 31: 2287-2298 - pdf - soldier ants (majors which block entrances with their heads) in the turtle ant Cephalotes rohweri are dynamically and adaptively allocated among multiple nests of the same colony

Powell S, Dornhaus A 2013 ‘Soldier-based defences dynamically track resource availability and quality in ants’, Animal Behaviour 85: 157-164 - pdf - see also above paper: soldiers in C. rohweri are adaptively allocated among nests but in a conservative bet-hedging strategy

Enemy assessment

Chapin KJ, Paat VA, Dornhaus A 2022 ‘Brood as booty: the effect of colony size and resource value in social insect contests’, Behavioral Ecology 33: 549-555 - pdf - Temnothorax colonies contest over brood (which can be eaten or raised as ‘slaves’ in the winner colony); we demonstrate that colonies can assess both their opponent’s and their own colony size (fighting ability) and resource value (amount of brood) to determine their contest strategy