Birn-Jeffery Aleksandra V, Higham Timothy E
Department of Biology, University of California Riverside, 900 University Avenue, Riverside, CA, 92521, USA
Department of Biology, University of California Riverside, 900 University Avenue, Riverside, CA, 92521, USA.
Integr Comp Biol. 2014 Dec;54(6):1159-72. doi: 10.1093/icb/icu015. Epub 2014 Apr 14.
Animals must continually respond dynamically as they move through complex environments, and slopes are a common terrain on which legged animals must move. Despite this, non-level locomotion remains poorly understood. In this study, we first review the literature on locomotor mechanics, metabolic cost, and kinematic strategies on slopes. Using existing literature we then performed scaling analyses of kinematic variables, including speed, duty factor, and stride-length across a range of body sizes from ants to horses. The studies that examined locomotion on inclines vastly outnumbered those focusing on declines. On inclines, animals tend to reduce speed and increase duty factor, but a similar consensus could not be reached for declines. Remarkably, stride-length did not differ between locomotion on inclines and on level terrain, but this may have resulted from data only being available for low slopes (<30°). On declines there appears to be a shift in locomotor strategy that is size-dependent. At masses <1-10 kg, animals tended to use shorter strides than on level terrain, and the opposite occurred at larger body masses. Therefore, possibly due to stability issues, body mass plays a significant role in the locomotor strategy used when traveling downhill. Although we currently lack sufficient data, differential leg function is likely to be critical for locomotion on slopes, with mechanical demands differing on limbs during movement on level, inclined, and declined surfaces. Our scaling analysis not only highlights areas that require future work, but also suggests that body size is important for determining the mechanics and strategies animals use to negotiate non-level terrain. It is clear that selection has resulted in an incredible range of body size among animals, both extant and extinct, and it is likely that the ability to move up and down slopes has constrained or relaxed these mechanical pressures. Given the lack of integration of ecological data with laboratory experiments, future work should first determine which inclines animals actually use in nature, as this likely plays a key role in behaviors such as predator-prey interactions.
动物在复杂环境中移动时必须不断做出动态反应，而斜坡是有腿动物必须移动的常见地形。尽管如此，非水平运动仍未得到充分理解。在本研究中，我们首先回顾了关于斜坡上运动力学、代谢成本和运动学策略的文献。然后利用现有文献，我们对一系列从蚂蚁到马的体型范围内的运动学变量进行了标度分析，包括速度、 Duty 因子和步长。研究倾斜面上运动的研究数量远远超过关注下倾面运动的研究。在倾斜面上，动物倾向于降低速度并增加 Duty 因子，但在下倾面上无法达成类似的共识。值得注意的是，倾斜面上的运动与水平地形上的运动之间步长没有差异，但这可能是因为只有低坡度（<30°）的数据可用。在下倾面上，运动策略似乎存在与体型相关的转变。在体重<1-10千克时，动物倾向于使用比在水平地形上更短的步长，而在更大体型时则相反。因此，可能由于稳定性问题，体重在下山时使用的运动策略中起着重要作用。虽然我们目前缺乏足够的数据，但不同的腿部功能可能对斜坡上的运动至关重要，因为在水平、倾斜和下倾表面上运动时肢体的机械需求不同。我们的标度分析不仅突出了需要未来开展工作的领域，还表明体型对于确定动物在非水平地形上移动所使用的力学和策略很重要。很明显，选择导致了现存和已灭绝动物之间令人难以置信的体型范围，并且上下坡移动的能力可能已经限制或缓解了这些机械压力。鉴于生态数据与实验室实验缺乏整合，未来的工作应该首先确定动物在自然界中实际使用的斜坡坡度，因为这可能在诸如捕食者 - 猎物相互作用等行为中起关键作用。
