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（例如海雀和鲣鸟）以高达24 m/s的速度潜水，作为捕猎机制之一；此外，海雀和鲣鸟拥有细长的颈部，这在高速撞击时的压缩状态下可能是身体最脆弱的部分。在本研究中，我们通过理解作用于头部的流体力与颈部柔韧性的相互作用，来探讨鸟类在俯冲潜水过程中颈部的稳定性。首先，我们利用一只回收的鸟类来确定俯冲潜水阶段。通过获取颅骨和颈部的解剖特征，以量化喙部几何形状和颈部肌肉对俯冲潜水稳定性影响的程度。其次，通过将弹性梁作为颈部模型并连接到类似颅骨的圆锥体上进行的物理实验，揭示了鸟类在潜水过程中颈部稳定性的极限，该极限取决于撞击速度和几何因素。我们发现，鸟类的颈部长度、颈部肌肉和潜水速度主要降低了俯冲潜水过程中的受伤风险。最后，我们利用研究结果来讨论人类为了避免受伤所能达到的最大潜水速度。