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 two coexisting species known to compete with each other: midday gerbils (Meriones meridianus, the dominant competitor) and three-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, while 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，动物都会在有其他觅食者在场的环境中开展觅食活动。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）。过往针对捕食者-猎物系统（predator-prey systems）的研究已证实，捕食者与猎物之间存在复杂的状态依赖性觅食博弈。本研究旨在探寻同功能群竞争者（intra-guild competitors）之间存在此类状态依赖性觅食博弈的证据。我们聚焦于一个沙漠啮齿类动物系统，该系统包含两种共存且存在竞争关系的物种：子午沙鼠（midday gerbil，*Meriones meridianus*，优势竞争者）与三趾跳鼠（three-toed jerboa，*Dipus sagitta*，劣势竞争者）。我们同时调控了两个物种的能量状态，并让它们在带有人工食物斑块的实验竞技场中进行觅食与互动。实验结果显示，两个物种均会对自身的能量状态做出响应，而处于饥饿状态的三趾跳鼠还会在食物收获量上显著响应子午沙鼠的能量状态。子午沙鼠在单独觅食时更倾向于将食物搬运至他处储存，但当三趾跳鼠在场时，则会切换为在食物斑块托盘上直接进食。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强烈。针对上述结果的一个合理解释是：对于饱腹的子午沙鼠而言，可储存食物的未来价值而非当前价值更为重要。与之相反，饥饿的子午沙鼠更倾向于即时进食，而非将三趾跳鼠完全排除在资源斑块之外。