Data from: State-dependent cooperation in burying beetles: parents adjust their contribution towards care based on both their own and their partner’s size

Handicapping experiments on species with biparental care show that a focal parent increases its contribution when its partner is handicapped. Such results are interpreted as evidence for negotiation, whereby each parent adjusts its amount of care to that of its partner. However, it is currently unclear whether the focal parent responds to a change in its handicapped partner's behaviour or state. To address this gap, we conducted an experiment on the burying beetle Nicrophorus vespilloides where we first experimentally generated different-sized male and female parents by varying the duration of larval development. We then used a 2×2 factorial design in which a small or large male was paired with a small or large female. Small females provided less direct care (food provisioning and interactions with larvae) than large females, and males and females provided less direct care when paired with a small partner. Thus, the focal parent adjusted its contribution towards care based on both its own state and that of its partner. There was evidence for negotiation between the two parents as the focal parent adjusted its contribution based on the amount of care by its partner. However, there was no evidence that negotiation accounted for how the focal parent responded to its partner's size. Our results have important implications for our understanding of biparental cooperation as they show that each parent not only adjusts its contribution based on the amount of care provided by its partner but also based on its own state and its partner's state.针对双亲抚育（biparental care）物种开展的负担操控实验（handicapping experiment）表明，当配偶被施加抚育负担时，目标亲代（focal parent）会提升自身的抚育投入量。此类结果被视为抚育协商（negotiation）机制的佐证：即每个亲代会根据配偶的抚育投入水平调整自身的抚育贡献。然而目前仍不清楚，目标亲代究竟是对负担施加后配偶的行为变化作出响应，还是对其生理状态变化作出响应。为填补这一研究空白，我们以埋葬甲（Nicrophorus vespilloides）为实验对象开展研究：首先通过调控幼虫发育时长，实验性地培育出体型大小各异的雌雄亲代；随后采用2×2因子设计（2×2 factorial design），将体型较小或较大的雄性分别与体型较小或较大的雌性进行配对。实验结果显示：相较于体型较大的雌性亲代，体型较小的雌性亲代提供的直接抚育（direct care）更少，具体包括食物投喂与幼虫互动行为；且当与体型较小的配偶配对时，雌雄亲代的直接抚育投入均有所减少。由此可见，目标亲代的抚育投入会同时依据自身状态与配偶状态进行调整。有证据表明双亲间存在抚育协商机制：目标亲代会根据配偶的抚育投入量调整自身贡献。但并无证据显示，抚育协商机制可解释目标亲代对配偶体型变化作出的响应。本研究结果对我们理解双亲抚育合作具有重要启示：研究表明，每个亲代不仅会根据配偶的抚育投入量调整自身贡献，还会同时结合自身状态与配偶状态进行相应调整。