Age polyethism can emerge from social learning: A game-theoretic investigation

Moein Khajehnejad, Julian García and Bernd Meyer

PLOS Computational Biology, 2025, vol. 21, issue 8, 1-22

Abstract: Age-polyethism—the age-based allocation of tasks in social insect colonies—is a key feature of division of labour. While its hormonal underpinnings have been studied extensively, the behavioural and environmental mechanisms driving age-polyethism remain poorly understood, especially under ecological stress. We present a novel modelling framework that integrates social learning with task-related environmental feedback to explain the emergence and breakdown of age-polyethism. We develop two models: a Social Learning (SL) model, in which individuals adapt task preferences by copying similar peers, and a Stimulus-Response Threshold Social Learning (SRT-SL) model, which extends this framework by incorporating task-related dynamic stimuli and response thresholds that regulate collective task demand. Our models demonstrate that age-polyethism can emerge from simple social imitation processes, without the need for fixed hormonal schedules. We show that under increasing environmental pressure (e.g., resource scarcity), age-polyethism collapses as younger individuals are forced into tasks typically handled by older workers. Importantly, we find that age-polyethism does not necessarily optimize immediate colony efficiency; instead, it appears to reflect a trade-off between environmental constraints and behavioural coordination. These findings provide a mechanistic and ecologically grounded explanation for empirical observations linking environmental stress to dysfunctional division of labour and colony collapse.Author summary: In many social insect colonies, like those of bees, workers perform different task sets at different ages (age polyethism). Commonly, younger individuals perform safe tasks inside the nest while older ones take on risky jobs like foraging. This age-based division of labour is often attributed to internal hormonal schedules, but how social behaviour and environmental stress affect this system is poorly understood. We developed a computer model to investigate these factors. In our model, individuals learn which tasks to perform by imitating other workers, paying more attention to their age peers. We then introduced environmental pressures to see how the self-organised division of labour would adjust. Our model shows that this simple form of social learning is enough for an age-based workforce structure to emerge that still maintains flexibility, without the requirement for a rigid internal clock. Crucially, when we applied strong environmental stress, this system collapsed and younger workers were forced into dangerous foraging tasks prematurely, which is consistent with empirical results. We also found that this division of labour may not be about maximizing day-to-day efficiency, but rather about ensuring long-term colony stability and resilience. These findings provide a new, mechanistic explanation for age polyethism and how environmental pressures can disrupt the social organization of a colony, offering key insights into the real-world problem of colony collapse.

Date: 2025
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Persistent link: https://EconPapers.repec.org/RePEc:plo:pcbi00:1013415

DOI: 10.1371/journal.pcbi.1013415

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