Data from: When should I be aggressive? A state-dependent foraging game between competitors

More often than not, animals forage with other foragers present. A foraging game may take place when the outcome of a forager’s actions depends on both its own and other foragers’ strategies. Previous studies on predator–prey systems have verified that complex state-dependent foraging games exist between predators and prey. In this study, we looked for evidence of such a state-dependent foraging game between intra-guild competitors. We studied a desert rodent system featuring 2 coexisting species known to compete with each other: midday gerbils (Meriones meridianus, the dominant competitor) and 3-toed jerboas (Dipus sagitta, the subordinate competitor). We simultaneously manipulated the energetic states of both species and allowed them to forage and interact in arenas with artificial food patches. We found that both species responded to their own energetic states, whereas hungry jerboas also significantly responded to gerbils’ energetic state in terms of food harvest. Gerbils preferred to carry food items away when foraging alone but switched to on-tray consumption when jerboas were present. Jerboas harvested more food when gerbils were hungry and the most intensive interference occurred when hungry jerboas encountered well-fed gerbils. A plausible explanation for these results is that the future rather than current value of cacheable food is more important to well-fed gerbils. In contrast, hungry gerbils prefer immediate consumption to completely excluding jerboas from resource patches.

在绝大多数情况下，动物的觅食活动都会有其他觅食者在场。当觅食者的行为结果同时取决于自身与其他觅食者的策略时，便会形成觅食博弈（foraging game）。此前针对捕食者-猎物系统的研究已证实，捕食者与猎物之间存在复杂的状态依赖型觅食博弈（state-dependent foraging game）。本研究旨在探寻功能群内竞争者（intra-guild competitors）之间存在此类状态依赖型觅食博弈的证据。我们以共存且存在种间竞争的两种沙漠啮齿类为研究对象：优势竞争者子午沙鼠（Meriones meridianus）与劣势竞争者三趾跳鼠（Dipus sagitta）。我们同步调控了两种啮齿类的能量状态，并让它们在带有人工食物斑块的行为试验箱中进行觅食与互动。结果显示，两种啮齿类均会响应自身的能量状态，而处于饥饿状态的三趾跳鼠还会根据子午沙鼠的能量状态调整其食物收获量。单独觅食时，子午沙鼠偏好将食物搬运至别处食用；但当三趾跳鼠在场时，它们会改为在托盘上直接取食。当子午沙鼠处于饥饿状态时，三趾跳鼠的食物收获量更高；而当饥饿的三趾跳鼠与饱腹的子午沙鼠相遇时，二者间的干扰行为最为剧烈。针对上述结果，一个合理的解释是：对于饱腹的子午沙鼠而言，可储存食物的未来价值比当前价值更为重要；与之相反，饥饿的子午沙鼠更倾向于直接取食，而非将三趾跳鼠完全排除在资源斑块之外。