How seabirds plunge-dive without injuries

In nature, several seabirds (e.g., gannets and boobies) dive into water at up to 24 m/s as a hunting mechanism; furthermore, gannets and boobies have a slender neck, which is potentially the weakest part of the body under compression during high-speed impact. In this work, we investigate the stability of the bird’s neck during plunge-diving by understanding the interaction between the fluid forces acting on the head and the flexibility of the neck. First, we use a salvaged bird to identify plunge-diving phases. Anatomical features of the skull and neck were acquired to quantify the effect of beak geometry and neck musculature on the stability during a plunge-dive. Second, physical experiments using an elastic beam as a model for the neck attached to a skull-like cone revealed the limits for the stability of the neck during the bird’s dive as a function of impact velocity and geometric factors. We find that the neck length, neck muscles, and diving speed of the bird predominantly reduce the likelihood of injury during the plunge-dive. Finally, we use our results to discuss maximum diving speeds for humans to avoid injury.

在自然界中，多种海鸟（如塘鹅（gannets）和鲣鸟（boobies））会以最高24 m/s的速度俯冲入水，以此作为捕猎手段；此外，塘鹅与鲣鸟拥有纤细的颈部，该部位在高速撞击过程中是身体承受压缩载荷的潜在薄弱环节。
本研究通过解析作用于头部的流体力与颈部柔性之间的相互作用，探究了此类鸟类在俯冲进水过程中颈部的稳定性。
首先，我们采用回收的鸟类标本确定俯冲进水的各个阶段，并获取头骨与颈部的解剖学特征，以此量化喙部几何形态与颈部肌肉组织对俯冲进水过程中颈部稳定性的影响。
其次，我们以弹性梁模拟颈部、将类头骨圆锥体作为头部模型开展物理实验，揭示了鸟类俯冲时颈部稳定性的极限——该极限随撞击速度与几何因素的变化而改变。
研究表明，鸟类的颈部长度、颈部肌肉组织与潜水速度，可显著降低俯冲进水过程中颈部受伤的可能性。
最后，我们基于本研究结果，探讨了人类为避免颈部受伤所能达到的最大潜水速度。