Department of Biological Sciences, University of Cincinnati, PO Box 210006, Cincinnati, OH 45221-0006, USA.
J Exp Biol. 2010 Dec 15;213(Pt 24):4249-56. doi: 10.1242/jeb.047225.
Arboreal habitats pose unique challenges for locomotion as a result of their narrow cylindrical surfaces and discontinuities between branches. Decreased diameter of branches increases compliance, which can pose additional challenges, including effects on stability and energy damping. However, the combined effects of substrate diameter and compliance are poorly understood for any animal. We quantified performance, kinematics and substrate deformation while boa constrictors (Boa constrictor) climbed vertical ropes with three diameters (3, 6 and 9 mm) and four tensions (0.5, 1.0, 1.5 and 2.0 body weights). Mean forward velocity decreased significantly with both decreased diameter and increased compliance. Both diameter and compliance had numerous effects on locomotor kinematics, but diameter had larger and more pervasive effects than compliance. Locomotion on the largest diameter had a larger forward excursion per cycle, and the locomotor mode and gripping strategy differed from that on the smaller diameters. On larger diameters, snakes primarily applied opposing forces at the same location on the rope to grip. By contrast, on smaller diameters forces were applied in opposite directions at different locations along the rope, resulting in increased rope deformation. Although energy is likely to be lost during deformation, snakes might use increased surface deformation as a strategy to enhance their ability to grip.
树栖生境因其狭窄的圆柱形表面和树枝之间的不连续性，给运动带来了独特的挑战。树枝直径的减小会增加顺应性，这可能会带来额外的挑战，包括对稳定性和能量阻尼的影响。然而，对于任何动物来说，基底直径和顺应性的综合影响都知之甚少。我们量化了蟒蛇（Boa constrictor）在攀爬三根直径（3、6 和 9 毫米）和四根张力（0.5、1.0、1.5 和 2.0 个体重）的垂直绳索时的表现、运动学和基底变形。平均前进速度随着直径的减小和顺应性的增加而显著降低。直径和顺应性都对运动学产生了许多影响，但直径的影响比顺应性更大、更普遍。在最大直径上的运动具有更大的每周期前进幅度，运动模式和抓握策略与较小直径上的不同。在较大的直径上，蛇主要在绳索的同一位置施加相反的力来抓握。相比之下，在较小的直径上，力在绳索上的不同位置沿相反的方向施加，导致绳索变形增加。尽管在变形过程中能量可能会损失，但蛇可能会将增加的表面变形用作增强抓握能力的策略。
