Socha John J, O'Dempsey Tony, LaBarbera Michael
Department of Organismal Biology and Anatomy, University of Chicago, Chicago, IL, 60637, USA, USA.
J Exp Biol. 2005 May;208(Pt 10):1817-33. doi: 10.1242/jeb.01579.
Flying snake species (Chrysopelea) locomote through the air despite a lack of appendages or any obvious external morphological specialization for flight. Here photogrammetric techniques were used to investigate C. paradisi's aerial trajectory in three dimensions. Two videocameras arranged in stereo were used to record head, midpoint and vent landmarks on snakes that jumped from a horizontal branch at a height of 9.62 m and landed in an open field. The coordinates of these landmarks were reconstructed in three dimensions and used to analyze patterns of position, glide angle and speed concurrently with changes in body posture in 14 glide sequences from different individuals. C. paradisi's trajectory was composed of a ballistic dive followed by a shallowing phase in which the path became more horizontal; for most glide trials, no equilibrium phase was observed. In the ballistic dive, the snake changed posture from generally straight to a wide 'S' shape in planview and began aerial undulation. Shortly after the ballistic dive, the snake's speed transitioned from an initial acceleration to stable or to a different rate of increase or decrease. Aerial undulation, in which high-amplitude traveling waves pass posteriorly down the body, was a prominent locomotor behavior. In mid-glide, this undulation occurred with the anterior body oriented approximately parallel with the ground and the posterior body cycling up and down in the vertical plane. The body angle of attack for the anterior body for one trial was 20-40 degrees . Snakes traveled a horizontal distance of 10.14+/-2.69 m (mean +/-s.d.) while reaching an airspeed of 10.0+/-0.9 m s(-1), sinking speed of 6.4+/-0.8 m s(-1) and horizontal speed of 8.1+/-0.9 m s(-1). The glide path shallowed at a rate of 20+/-6 degrees s(-1) and reached a minimum glide angle of 28+/-10 degrees , with a minimum recorded glide angle of 13 degrees . C. paradisi are surprisingly good gliders given their unconventional locomotor style, with performance characteristics that rival or surpass more familiar gliding taxa such as flying squirrels. As in other gliders, C. paradisi is potentially capable of using aerial locomotion to move effectively between trees, chase aerial prey, or avoid predators.
飞蛇属（金花蛇属）的蛇类尽管没有用于飞行的附肢或任何明显的外部形态特化结构，却能在空中移动。在此，我们运用摄影测量技术对天堂金花蛇的三维空中轨迹进行了研究。使用两台呈立体排列的摄像机，记录从9.62米高处的水平树枝上跳下并落在开阔场地的蛇的头部、中点和泄殖腔等标志点。这些标志点的坐标被重建为三维坐标，并用于分析来自不同个体的14次滑行序列中位置、滑翔角和速度模式，同时分析身体姿势的变化。天堂金花蛇的轨迹由一个弹道式俯冲阶段和随后的变浅阶段组成，在变浅阶段路径变得更加水平；在大多数滑翔试验中，未观察到平衡阶段。在弹道式俯冲阶段，蛇在平面视图中从大致笔直的姿势转变为宽阔的“S”形，并开始空中波动。在弹道式俯冲后不久，蛇的速度从初始加速转变为稳定状态，或转变为不同的增减速率。空中波动是一种显著的运动行为，即高振幅的行波沿身体向后传播。在滑行中期，这种波动发生时，蛇的前半身大致与地面平行，而后半身在垂直平面内上下循环。在一次试验中，前半身的攻角为20 - 40度。蛇在达到空速10.0±0.9米/秒、下沉速度6.4±0.8米/秒和水平速度8.1±0.9米/秒的同时，水平移动距离为10.14±2.69米（平均值±标准差）。滑翔路径以20±6度/秒的速率变浅，达到最小滑翔角28±10度，记录到的最小滑翔角为13度。鉴于其非常规的运动方式，天堂金花蛇是令人惊讶的优秀滑翔者，其性能特征可与或超过更常见的滑翔类群，如鼯鼠。与其他滑翔动物一样，天堂金花蛇有可能利用空中运动在树木间有效移动、追逐空中猎物或躲避捕食者。
