AERIAL MANEUVERS OF LEAPING LEMURS - THE PHYSICS OF WHOLE-BODY ROTATIONS WHILE AIRBORNE
AERIAL MANEUVERS OF LEAPING LEMURS - THE PHYSICS OF WHOLE-BODY ROTATIONS WHILE AIRBORNE
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DOI：
10.1002/ajp.1350160402
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发表时间：
1988-01-01
影响因子：
2.4
通讯作者：
DUNBAR, DC
中科院分区：
文献类型：
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作者：
DUNBAR, DC
一些原猿物种从一个垂直的支撑物开始跳跃，背部朝向着陆的目标。为了重新调整自己的方向，从背朝上，头朝前的起跳到腹朝上，脚先着地，动物们结合了最初的扭转和部分向后翻筋斗。一群环尾狐猴（Lumer catta）的电影显示，在从垂直极点跳到水平支撑物的过程中，当动物在空中时，往往会开始向后翻筋斗。这些原星如何在没有外力的情况下开始旋转而不违反角动量守恒？该问题通过矢量分析来解决，以演示从拍摄序列中提取的一系列关键身体位置的三个主要（对称）旋转轴的角动量(H)变化。一个L. catta标本被分割，以提供建模各种身体位置所需的尺寸和重量。这些数据也被用来计算三个主轴的转动惯量，以预测这些轴的转动是稳定的还是亚稳的。像任何抛射物一样，狐猴在起飞时必须保持总角动量（HT）。然而，HT是一个矢量，它是关于三个主轴的分量矢量的结果。因此，只要HT保持不变，关于各个轴的H可能会改变。有策略地计时尾巴运动使身体倾斜，从而改变从头到脚（扭转）轴的H值。为了保存，HT，也沿着扭转轴对齐，角动量转移到翻筋斗轴。由于甩尾的方向，最初的旋转是部分向后翻筋斗，使后肢向前着地。这种启动特定旋转的策略与人类跳板潜水员的练习相似。
Several prosimian species begin a leap from a vertical support with their back toward the landing target. To reorient themselves from this dorsally facing, head-first lift-off to a ventrally facing, feet-first landing, the animals combine an initial twist with a partial backward somersault. Cinefilms of a ceptive colony of ringtailed lemurs (Lumer catta) revealed that during leaps from vertical poles to horizontal supports, the backward somersaulting rotations were often initiated while the animals were airborne. How could these prosimians initiate rotations in the absence of externally applied forces without violating angular momentum conservation? The problem was approached through vector analysis to demonstrate angular momentum (H) changes about the three principal (symmetrical) axes of rotation for a series of critical body positions that were extracted from the filmed sequences. One L. catta specimen was segmented to provide the dimensions and weights necessary for modeling the various body positions. These data were also used to calculate moments of inertia about the three principal axes in order to predict if rotations about these axes were stable or metastable. Lemurs, like any projectile, must conserve the total angular momentum (HT) established a lift-off. HT, however, is a vector quantity that is the resultant of component vectors about the three principal axes. Thus, H about the individual axes may change as long as HT remians constant. Strategically timed tail movements tilted the body, thereby changing the H value about the head-to-toe (twisting) axis. To conserve, HT, also aligned along the twisting axis, angular momentum transferred to the somersaulting axis. Owing to the direction of tail-throw, the initiated rotations were partial backward somersaults that brought the hindlimbs forward for landing. This strategy for initiating specific rotations parallels that practiced by human springboard divers.