Data from: Food sharing in vampire bats: reciprocal help predicts donations more than relatedness or harassment

Common vampire bats often regurgitate food to roost-mates that fail to feed. The original explanation for this costly helping behaviour invoked both direct and indirect fitness benefits. Several authors have since suggested that food sharing is maintained solely by indirect fitness because non-kin food sharing could have resulted from kin recognition errors, indiscriminate altruism within groups, or harassment. To test these alternatives, we examined predictors of food-sharing decisions under controlled conditions of mixed relatedness and equal familiarity. Over a 2-year period, we individually fasted 20 vampire bats (Desmodus rotundus) and induced food sharing on 48 of 52 days. Surprisingly, donors initiated food sharing more often than recipients, which is inconsistent with harassment. Food received was the best predictor of food given, and 8.5 times more important than relatedness. Sixty-four percent of dyads were unrelated, approaching the 67% expected if nepotism was absent. Consistent with social bonding, the food-sharing network was consistent and correlated with mutual allogrooming. Together with past work, these findings support the hypothesis that food sharing in vampire bats provides mutual direct fitness benefits, and is not explained solely by kin selection or harassment.普通吸血蝠（Common vampire bats）常会将反刍的食物分享给未能成功觅食的栖息同伴。针对这种需付出适合度代价的互助行为，最初的解释同时纳入了直接适合度与间接适合度收益两个维度。后续诸多研究者提出，食物分享仅可通过间接适合度得以维持，因为非亲缘个体间的食物分享可能源自亲缘识别误差、群体内的无差别利他行为，抑或是施助者遭受骚扰后的被迫分享。为验证这些不同假说，我们在亲缘关系混杂且个体间熟悉程度均等的可控实验条件下，探究了食物分享决策的影响因子。在为期2年的实验周期中，我们对20只普通吸血蝠（Desmodus rotundus）进行个体禁食处理，并在52天的观测周期内，有48天成功诱导出食物分享行为。令人意外的是，食物分享多由施予方主动发起，而非接收方，这一结果与骚扰假说相悖。接收的食物量是预测施予食物量的最优因子，其影响力是亲缘关系的8.5倍。64%的配对个体间不存在亲缘关系，这一比例接近无亲缘偏好时的理论预期值67%。与社会纽带的理论预期一致，食物分享网络具有稳定性，且与个体间的相互理毛行为显著相关。结合既往研究成果，本研究结果支持吸血蝠的食物分享可带来双向直接适合度收益的假说，而非仅能通过亲缘选择或受骚扰被迫分享来解释。