Behavioral implications of ontogenetic changes in intrinsic hand and foot proportions in olive baboons (Papio Anubis)

International audienc

Small vertebrates running on uneven terrain: a biomechanical study of two differently specialised lacertid lizards

While running, small animals frequently encounter large terrain variations relative to their body size, therefore, terrain variations impose important functional demands on small animals. Nonetheless, we have previously observed in lizards that running specialists can maintain a surprisingly good running performance on very uneven terrains. The relatively large terrain variations are ofset by their capacity for leg adjustability that ensures a ‘smooth ride’ of the centre of mass (CoM). The question as to how the efect of an uneven terrain on running performance and locomotor costs difers between species exhibiting diverse body build and locomotor specializations remains. We hypothesise that specialized runners with long hind limbs can cross uneven terrain more efciently than specialized climbers with a dorso-ventrally fattened body and equally short fore and hind limbs. This study reports 3D kinematics using high-speed videos (325Hz) to investigate leg adjustability and CoM movements in two lacertid lizards (Acanthodactylus boskianus, running specialist; Podarcis muralis, climbing specialist). We investigated these parameters while the animals were running on a level surface and over a custommade uneven terrain. We analysed the CoM dynamics, we evaluated the fuctuations of the positive and negative mechanical energy, and we estimated the overall cost of transport. Firstly, the results reveal that the climbers ran at lower speeds on fat level terrain but had the same cost of transport as the runners. Secondly, contrary to the running specialists, the speed was lower and the energy expenditure higher in the climbing specialists while running on uneven terrain. While leg movements adjust to the substrates’ variations and enhance the stability of the CoM in the running specialist, this is not the case in the climbing specialist. Although their legs are kept more extended, the amplitude of movement does not change, resulting in an increase of the movement of the CoM and a decrease in locomotor efciency. These results are discussed in light of the respective (micro-)habitat of these species and suggest that energy economy can also be an important factor for small vertebrates

Impressive arboreal gap-crossing behaviors in wild bonobos, pan paniscus

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