Data from: The shortfall of sociality: group-living affects hunting performance of individual social spiders

Ineffective hunters in cooperative foraging groups may be shielded from natural selection by their more effective group mates, whereas those living solitarily would starve and thus be removed from the population. The problem may be exacerbated in large groups where it may be easier for individuals to withhold participation. Group foragers may thus be ineffective individual hunters or exhibit greater inter-individual variation in hunting abilities, in particular when living in large groups. We test these hypotheses in spider species of the genus Anelosimus that differ in their level of sociality and, among social species, in colonies of different sizes. We found that individuals from the more social species, and those from larger groups, reacted more slowly to prey than those from solitary species or small groups. Individuals from these categories also had greater inter-individual variation in reaction times. Individuals from large social groups also had lower prey capture success than those from small ones. These differences may have been driven by the size of the group from which the social individuals were taken, as those from small colonies behaved similarly to individuals of the two less social species. This finding suggests that hunting ability may develop as a phenotypically plastic trait.

在合作觅食群体中，狩猎效率低下的个体或许会被更高效的同伴庇护，免于自然选择的淘汰；而独居的低效猎手则会因饥饿被从种群中移除。在大型群体中，个体更易逃避参与觅食，这一问题会愈发严重。因此，群体觅食者或许本身就是低效的个体猎手，或是狩猎能力的个体间差异更大，尤其是在大型群体中生存时。我们以社会性水平各异的栉足蛛属（Anelosimus）蜘蛛物种为研究对象，并针对社会性物种选取不同规模的蛛群验证上述假说。研究发现，相较于独居物种或小型蛛群的个体，社会性更强的物种以及大型蛛群中的个体，对猎物的反应更为迟缓。这类个体的反应时也存在更大的个体间差异。大型社会性蛛群的个体，其猎物捕获成功率也低于小型蛛群的个体。这些差异或许由社会性个体所在的群体规模所驱动，因为小型蛛群的个体行为与两种低社会性物种的个体较为相似。该研究结果表明，狩猎能力或许可作为一种表型可塑性性状（phenotypically plastic trait）演化形成。