Impressive Arboreal Gap-Crossing Behaviors in Wild Bonobos, Pan paniscus

摘要

Most primates are arboreal, and the current context of habitat fragmentation makes gap- and road-crossing behaviors more and more common. Great apes may try to avoid behaviors such as arboreal leaping because given their size such behaviors are risky. Here, we report impressive gap-crossing by wild bonobos (Pan paniscus) in the Democratic Republic of Congo, induced by human disturbance and habitat fragmentation. We quantify the basic mechanics of leaps and arboreal landing performance in two individuals. The bonobos climbed a tree, 15 m high, and performed pronograde leaps between thin flexible branches, to grasp landing branches ca. 4 m further and below their starting point. They reached an instantaneous velocity of about 9 m center dot s(-1). The bonobos used pendular swinging of landing branches to dissipate the kinetic energy built up during falling, requiring a grip force of about 2.5x body weight. Moreover, our results show that bonobos might be able to modulate the drag experienced during falling (up to 20% of body weight) by adjusting their posture. Apparently, bonobos evaluate the structural context to perform the best possible leap and balance the risks against the extra energetic costs involved. Further study of locomotor performance is needed to inform conservation planning, owing to the extent of habitat fragmentation due to human activities.