Dynamics and Energetics of Bottlenose Dolphins (Tursiops truncatus) Fluke-and-Glide Gait

Intermittent locomotion composed of periods of active flapping/stroking followed by inactive gliding has been observed with species that inhabit both aerial and marine environments. However, studies on the energetic benefits of a fluke-and-glide (FG) gait during horizontal locomotion are limited for dolphins. This work presents a physics-based model of FG gait and analysis of the associated costs of transport of bottlenose dolphins (Tursiops truncatus). New estimates of gliding drag coefficients for the model were estimated experimentally from free-swimming bottlenose dolphins. The data-driven approach used kinematic measurement from 84 hours of biologging tag data collected from 3 animals to estimate the coefficients. A set of 532 qualified gliding events were automatically extracted for gliding drag coefficient estimation, and an additional 783 FG bouts were parameterized and used to inform the model-based dynamic analysis. Experimental results indicate that FG gait was preferred at speeds around 2.2 - 2.7 m/s. Observed FG bouts had an average duty factor of 0.45 and gliding duration of 5 sec. The average associated metabolic cost of transport (COT) and mechanical cost of transport (MECOT) of FG gait are 2.53 and 0.35 J · m−1 · kg−1 at the preferred speeds. This corresponded to an 18.9% and 27.1% reduction in cost when compared to modeled continuous fluking gait at the same reference speed. Average thrust was positively correlated with fluking frequency and amplitude as animals accelerated during the FG bouts. While fluking frequency and amplitude were negatively correlated for a given thrust range. These results support the supposition that FG gait enhances the horizontal swimming efficiency of bottlenose dolphins and provides new dynamical insights into the gait of these animals.

在天空和海洋环境中栖息的物种都被观察到存在由主动拍打/划动阶段和随后的非主动滑行阶段组成的间歇性运动。然而，对于海豚在水平运动过程中采用摆尾滑行（FG）步态的能量优势的研究还很有限。这项工作提出了一个基于物理的FG步态模型，并对宽吻海豚（Tursiops truncatus）的相关运输成本进行了分析。该模型中滑行阻力系数的新估计值是通过对自由游动的宽吻海豚进行实验得出的。这种数据驱动的方法利用从3只动物身上收集的84小时生物记录标签数据的运动学测量来估计这些系数。自动提取了532个合格的滑行事件用于滑行阻力系数估计，另外还对783个FG回合进行了参数化，并用于为基于模型的动态分析提供信息。实验结果表明，在速度约为2.2 - 2.7 m/s时，FG步态更受青睐。观察到的FG回合平均占空比为0.45，滑行持续时间为5秒。在首选速度下，FG步态相关的平均代谢运输成本（COT）和机械运输成本（MECOT）分别为2.53和0.35 J·m⁻¹·kg⁻¹。与在相同参考速度下模拟的连续摆尾步态相比，成本分别降低了18.9%和27.1%。在FG回合中，随着动物加速，平均推力与摆尾频率和幅度呈正相关。而在给定的推力范围内，摆尾频率和幅度呈负相关。这些结果支持了FG步态提高宽吻海豚水平游泳效率的假设，并为这些动物的步态提供了新的动力学见解。