Higham Timothy E, Russell Anthony P, Niklas Karl J
Department of Biology, University of California, Riverside, CA 92521, USA
Department of Biological Sciences, University of Calgary, Calgary, Alberta, Canada T2N 1N4.
J R Soc Interface. 2017 Jun;14(131). doi: 10.1098/rsif.2017.0156.
The remarkable adhesive capabilities of geckos have garnered attention from scientists and the public for centuries. Geckos are known to have an adhesive load-bearing capacity far in excess (by 100-fold or more) of that required to support their body mass or accommodate the loading imparted during maximal locomotor acceleration. Few studies, however, have investigated the ecological contexts in which geckos use their adhesive system and how this may influence its properties. Here we develop a modelling framework to assess whether their prodigious adhesive capacity ever comes under selective challenge. Our investigation is based upon observations of escape-induced aerial descents of canopy-dwelling arboreal geckos that are rapidly arrested by clinging to leaf surfaces in mid-fall. We integrate ecological observations, adhesive force measurements, and body size and shape measurements of museum specimens to conduct simulations. Using predicted bending mechanics of petioles and leaf midribs, we find that the drag coefficient of the gecko, the size of the gecko and the size of the leaf determine impact forces. Regardless of the landing surface, safety factors for geckos range from a maximum of just over 10 to a minimum of well under one, which would be the point at which the adhesive system fails. In contrast to previous research that intimates that gecko frictional adhesive capacity is excessive relative to body mass, we demonstrate that realistic conditions in nature may result in frictional capacity being pushed to its limit. The rapid arrest of the lizard from its falling velocity likely results in the maximal loading to which the adhesive system is exposed during normal activities. We suggest that such activities might be primary determinants in driving their high frictional adhesive capacity.
几个世纪以来，壁虎非凡的粘附能力一直吸引着科学家和公众的关注。众所周知，壁虎的粘附承重能力远远超过（达100倍或更多）支撑其体重或承受最大运动加速时所施加负荷所需的能力。然而，很少有研究调查壁虎使用其粘附系统的生态环境，以及这可能如何影响其性能。在这里，我们开发了一个建模框架，以评估它们惊人的粘附能力是否曾面临选择性挑战。我们的研究基于对栖息在树冠层的树栖壁虎在逃避时空中下降的观察，这些壁虎在下落过程中通过 clinging to leaf surfaces 迅速停止。我们整合了生态观察、粘附力测量以及博物馆标本的身体大小和形状测量数据来进行模拟。利用叶柄和叶片中脉的预测弯曲力学，我们发现壁虎的阻力系数、壁虎的大小和叶片的大小决定了冲击力。无论着陆表面如何，壁虎的安全系数范围从最高略超过10到最低远低于1，而安全系数为1时粘附系统就会失效。与之前暗示壁虎摩擦粘附能力相对于体重过高的研究不同，我们证明自然环境中的实际情况可能会使摩擦能力达到极限。蜥蜴从下落速度迅速停止可能会导致粘附系统在正常活动中承受最大负荷。我们认为，此类活动可能是促使它们具有高摩擦粘附能力的主要决定因素。 （注：原文中“clinging to leaf surfaces”这里的“clinging to”似乎有误，结合语境推测可能是“contacting”之类的词，但按要求未修改原文直接翻译）
