Netlogo_model_2022_01_07_caches_Serafino.nlogo from Temporary prey storage along swarm columns of army ants: an adaptive strategy for successful raiding?

While pillaging the brood of other ant colonies, Eciton army ants accumulate prey in piles, or caches, along their foraging trails. Widely documented, these structures have historically been considered as by-products of heavy traffic or aborted relocations of the ants' temporary nest, or bivouac. However, we recently observed that caches of the hook-jawed army ant, Eciton hamatum, appeared independently from heavy traffic or bivouac relocations. In addition, the flow of prey through caches varied based on the quantity of prey items workers transported. As this suggested a potential adaptive function, we developed agent-based simulations to compare raids of caching and non-caching virtual army ants. We found that caches increased the amount of prey that relatively low numbers of raiders were able to retrieve. However, this advantage became less conspicuous—and generally disappeared—as the number of raiders increased. Based on these results, we hypothesize that caches maximize the amount of prey that limited amounts of raiders can retrieve, especially as prey colonies coordinately evacuate their brood. In principle, caches also allow workers to safely collect multiple-prey items and efficiently transport them to the bivouac. Further field observations are needed to test this and other hypotheses emerging from our study.

在劫掠其他蚁群幼体的过程中，游蚁属（Eciton）行军蚁会在觅食路径沿线堆积猎物，形成猎物堆或贮藏点（caches）。这类结构已被广泛记录，长期以来被视作蚁群繁忙通行的副产物，或是其临时宿营地（bivouac）搬迁中止的产物。然而我们近期观察到，钩颚游蚁（Eciton hamatum）的贮藏点并非由繁忙通行或临时宿营地搬迁所产生。此外，经贮藏点转运的猎物流量会随工蚁搬运的猎物数量变化而产生波动。鉴于这一现象暗示其可能存在适应性功能，我们开发了基于智能体（Agent）的模拟模型，对比了存在贮藏行为与无贮藏行为的虚拟行军蚁的劫掠活动。结果显示，当劫掠队伍数量相对较少时，贮藏点可提升劫掠者所能运回的猎物总量。但随着劫掠者数量增加，这一优势会逐渐弱化，最终通常完全消失。基于上述结果，我们提出假说：贮藏点可最大化有限规模劫掠队伍所能运回的猎物总量，尤其是当猎物蚁群协同疏散其幼体时。从理论上讲，贮藏点还能让工蚁安全收集多件猎物，并高效将其转运至临时宿营地。仍需开展进一步的野外观察，以验证本研究提出的这一假说及其他衍生假说。