Penning David A, Moon Brad R
Department of Biology, University of Louisiana at Lafayette, Lafayette, LA 70504-43602, USA
Department of Biology and Environmental Health, Missouri Southern State University, Joplin, MO 64801, USA.
J Exp Biol. 2017 Mar 15;220(Pt 6):1154-1161. doi: 10.1242/jeb.147082.
Across ecosystems and trophic levels, predators are usually larger than their prey, and when trophic morphology converges, predators typically avoid predation on intraguild competitors unless the prey is notably smaller in size. However, a currently unexplained exception occurs in kingsnakes in the genus Kingsnakes are able to capture, constrict and consume other snakes that are not only larger than themselves but that are also powerful constrictors (such as ratsnakes in the genus ). Their mechanisms of success as intraguild predators on other constrictors remain unknown. To begin addressing these mechanisms, we studied the scaling of muscle cross-sectional area, pulling force and constriction pressure across the ontogeny of six species of snakes (, , , , and ). Muscle cross-sectional area is an indicator of potential force production, pulling force is an indicator of escape performance, and constriction pressure is a measure of prey-handling performance. Muscle cross-sectional area scaled similarly for all snakes, and there was no significant difference in maximum pulling force among species. However, kingsnakes exerted significantly higher pressures on their prey than ratsnakes. The similar escape performance among species indicates that kingsnakes win in predatory encounters because of their superior constriction performance, not because ratsnakes have inferior escape performance. The superior constriction performance by kingsnakes results from their consistent and distinctive coil posture and perhaps from additional aspects of muscle structure and function that need to be tested in future research.
在整个生态系统和营养级中，捕食者通常比它们的猎物更大，当营养形态趋同时，捕食者通常会避免捕食同域竞争物种，除非猎物的体型明显更小。然而，目前有一个无法解释的例外情况发生在王蛇属中。王蛇能够捕获、绞杀并吃掉其他蛇类，这些蛇不仅比它们自身更大，而且还是强大的绞杀者（比如锦蛇属中的蛇类）。它们作为对其他绞杀者的同域捕食者取得成功的机制仍然未知。为了开始探究这些机制，我们研究了六种蛇（[具体六种蛇的属名]）在个体发育过程中肌肉横截面积、拉力和绞杀压力的缩放情况。肌肉横截面积是潜在力量产生的一个指标，拉力是逃脱能力的一个指标，而绞杀压力是猎物处理能力的一种度量。所有蛇类的肌肉横截面积缩放情况相似，并且不同物种之间的最大拉力没有显著差异。然而，王蛇对猎物施加的压力明显高于锦蛇。物种之间相似的逃脱能力表明，王蛇在捕食遭遇中获胜是因为它们卓越的绞杀能力，而不是因为锦蛇的逃脱能力较差。王蛇卓越的绞杀能力源于它们一致且独特的盘绕姿势，或许还源于肌肉结构和功能的其他方面，这些方面有待未来的研究进行验证。
