Resource ephemerality influences effectiveness of altruistic behavior in collective foraging

Abstract

In collective foraging, interactions between conspecifics can be exploited to increase foraging efficiencies. Many collective systems exhibit short interaction ranges, making information about patches rich in resources only locally available. In environments wherein these patches are difficult to locate, collective systems might exhibit altruistic traits that increase average resource intake compared to non-interacting systems. In this work, we show that resource ephemerality and availability highly influence the benefits of altruistic behavior. We study an agent-based model wherein foragers can recruit others to feed on patches, instead of exploiting these individually. We show that the net gain by recruiting conspecifics can be estimated, effectively reducing the decision on patch detection to one based on a threshold. Patches with qualities above this threshold are expected to increase foraging efficiencies and should therefore induce recruiting of others. By letting foragers assume Levy searches, we show that recruitment strategies with contrasting diffusion characteristics optimize conspecific encounter rates. Our results further indicate that active recruitment is only beneficial when patches are scarce and persistent. Most interestingly, the effect of choosing suboptimal threshold values is small over a wide range of resource ephemeralities. This suggests that the decision of whether to recruit others is more impactful than fine-tuning the recruitment decision. Finally, we show that the advantages of active recruitment depend greatly on both forager density and their interaction radius, as we observe passive strategies to be more efficient, but only when forager densities or interaction ranges are large.