Liu Q, Simpson K, Izar P, Ottoni E, Visalberghi E, Fragaszy D
Department of Psychology, University of Georgia, Athens, GA 30602, USA.
Am J Phys Anthropol. 2009 Feb;138(2):210-20. doi: 10.1002/ajpa.20920.
Wild bearded capuchins (Cebus libidinosus, quadrupedal, medium-sized monkeys) crack nuts using large stones. We examined the kinematics and energetics of the nut-cracking action of two adult males and two adult females. From a bipedal stance, the monkeys raised a heavy hammer stone (1.46 and 1.32 kg, from 33 to 77% of their body weight) to an average height of 0.33 m, 60% of body length. Then, they rapidly lowered the stone by flexing the lower extremities and the trunk until the stone contacted the nut. A hit consisting of an upward phase and a downward phase averaged 0.74 s in duration. The upward phase lasted 69% of hit duration. All subjects added discernable energy to the stone in the downward phase. The monkeys exhibited individualized kinematic strategies, similar to those of human weight lifters. Capuchins illustrate that human-like bipedal stance and large body size are unnecessary to break tough objects from a bipedal position. The phenomenon of bipedal nut-cracking by capuchins provides a new comparative reference point for discussions of percussive tool use and bipedality in primates.
野生卷尾猴（僧面猴属，四足行走的中型猴子）会使用大石头砸开坚果。我们研究了两只成年雄性和两只成年雌性卷尾猴砸坚果动作的运动学和能量学。猴子从双足站立姿势将沉重的锤石（分别为1.46千克和1.32千克，占其体重的33%至77%）举到平均0.33米的高度，即体长的60%。然后，它们通过弯曲下肢和躯干迅速将石头放下，直到石头碰到坚果。一次包括向上和向下阶段的敲击平均持续时间为0.74秒。向上阶段持续敲击持续时间的69%。所有受试猴子在向下阶段都给石头增加了可察觉的能量。这些猴子表现出个性化的运动策略，类似于人类举重运动员。卷尾猴表明，类似人类的双足站立姿势和大体型对于从双足位置打破坚硬物体并非必要。卷尾猴双足砸坚果的现象为灵长类动物使用敲击工具和双足行走的讨论提供了一个新的比较参考点。
