In many organisms, juveniles have performance capabilities that partly offset their disadvantageous sizes. Using high‐speed video recordings and imaging software, we measured the scaling of head morphology, axial morphology, and defensive strike performance of Pantherophis obsoletus across their ontogeny to understand how size and morphology affect performance. Head measurements were negatively allometric whereas the cross‐sectional area (CSA) of epaxial muscles displayed positive allometry. The greater relative muscle CSA of larger ratsnakes allows them to produce higher forces relative to their mass, and those forces act on a relatively smaller head mass when it is thrust forward during striking. Maximum strike accelerations of 70–273.8 ms⁻² and velocities of 1.08–3.39 ms⁻¹ scaled positively with body mass but differed from the geometric predictions. Velocity scaled with mass^0.15 and acceleration scaled with mass^0.17. Larger snakes struck from greater distances (range = 4.1–26 cm), but all snakes covered the strike distances with similarly short durations (84 ± 3 ms). The negatively allometric head size, isometry of anterior mass, and positively allometric muscle CSA enable larger P. obsoletus to strike with higher velocities and accelerations than smaller individuals. Our results contrast with the scaling of strike performance in an arboreal viper, whose strike distance and velocity were independent of body mass. When strike distance is modulated, all other performance capacities are affected because of the interdependence of acceleration, velocity, duration, and distance.

中文翻译：

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西部大鼠（Pantherophis obsoletus）的地面打击表现的尺度。

在许多生物中，幼鱼的生产能力可以部分抵消其不利的大小。使用高速视频记录和成像软件，我们测量了Pantherophis obsoletus在其个体发育过程中头部形态，轴向形态和防御性打击表现的比例，以了解尺寸和形态如何影响表现。头部测量结果为负异形，而远侧肌肉的横截面积（CSA）显示为正异形。较大的响尾蛇较大的相对肌肉CSA允许它们产生相对于其质量的更大的力，并且在打击过程中向前推动时，这些力作用在相对较小的头部质量上。最大打击加速度为70–273.8 ms ^-2，速度为1.08–3.39 ms^-1与体重成正比，但与几何预测不同。速度以质量^0.15缩放，加速度以质量^0.17缩放。较大的蛇从较远的距离（范围= 4.1–26 cm）处进行打击，但是所有蛇都以同样短的持续时间（84±3 ms）覆盖了打击距离。负向异形的头部大小，前部肿块的等距和正向异形的肌肉CSA可使较大的P.obsoletus比较小的个体具有更高的速度和加速度。我们的结果与树栖vi蛇的打击性能成比例形成对比，该行为的打击距离和速度与体重无关。调节打击距离后，由于加速度，速度，持续时间和距离之间的相互依赖关系，所有其他性能都会受到影响。