Data from: Quantifying the effect of gape and morphology on bite force: biomechanical modeling and in vivo measurements in bats

Maximum bite force is an important metric of feeding performance that defines the dietary ecology of many vertebrates. In mammals, theoretical analyses and empirical studies suggest a trade-off between maximum bite force and gape at behavioural and evolutionary scales; in vivo bite force is expected to decrease at wide gapes, and cranial morphologies that enable high mechanical advantage are thought to have a lower ability to generate high bite forces at wide gapes, and vice versa. However, very few studies have confirmed these relationships in free-ranging mammals. This study uses an ecologically diverse sample of bats to document the variation in bite force with respect to gape angle, and applies three-dimensional models of the feeding apparatus to identify the major morphological and biomechanical predictors of the gape-bite force relationship. In vivo and model data corroborated that bite force decreases significantly at wide gapes across species, but there is substantial intraspecific variation in the data obtained from live bats. Results from biomechanical models, analysed within a phylogenetic framework, revealed that species with larger temporalis muscles, higher temporalis stretch factors and high mechanical advantages experience a steeper reduction in bite force with increasing gape. These trends are illustrated by short-faced durophagous frugivores. The results from this study suggest that gape-mediated changes in bite force can be explained both by behavioural effects and cranial morphology, and that these links are relevant for functional analyses of mammal dietary ecology.最大咬合力（maximum bite force）是评估取食性能的关键度量指标，同时也是界定多数脊椎动物食性生态的核心依据。 在哺乳动物类群中，理论分析与实证研究均表明，在行为与进化尺度上，最大咬合力与张口度（gape）之间存在权衡关系：体内（in vivo）测得的咬合力在大张口角度下会出现显著下降，而具备高机械优势（mechanical advantage）的颅骨形态，在大张口时产生高咬合力的能力往往更弱，反之亦然。然而，目前极少有研究在自由活动的野生哺乳动物中验证过这些关联。 本研究选取食性生态多样的蝙蝠类群作为样本，记录了咬合力随张口角度变化的规律，并借助取食器官（feeding apparatus）的三维模型，解析了张口度-咬合力关联关系的主要形态学与生物力学预测因子。 体内实测数据与模型结果均证实，跨物种而言，大张口角度下咬合力会显著下降，但从活体蝙蝠获取的数据中存在显著的种内变异。基于系统发育框架分析的生物力学模型结果显示，颞肌（temporalis muscles）体积更大、颞肌拉伸系数更高且机械优势更强的物种，其咬合力随张口度增加的下降幅度更为陡峭。短面型食硬质果实的植食类群恰好印证了这一趋势。 本研究结果表明，由张口度介导的咬合力变化，可同时通过行为效应与颅骨形态予以解释，且这些关联对哺乳动物食性生态的功能分析具有重要参考价值。