Rader Jonathan A, Hedrick Tyson L
Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.
J Exp Biol. 2024 Aug 1;227(15). doi: 10.1242/jeb.246828.
Animals must tune their physical performance to changing environmental conditions, and the breadth of environmental tolerance may contribute to delineating the geographic range of a species. A common environmental challenge that flying animals face is the reduction of air density at high elevation and the reduction in the effectiveness of lift production that accompanies it. As a species, turkey vultures (Cathartes aura) inhabit a >3000 m elevation range, and fly considerably higher, necessitating that they accommodate for a 27% change in air density (0.890 to 1.227 kg m-3) through behavior, physiology or biomechanics. We predicted that birds flying at high elevation would maintain aerodynamic lift performance behaviorally via higher flight speeds, rather than increases in power output or local phenotypic adaptation. We used three-dimensional videography to track turkey vultures flying at three elevations, and data supported the hypothesized negative relationship between median airspeed and air density. Additionally, neither the ratio of horizontal speed to sinking speed nor flapping behavior varied with air density.
动物必须根据不断变化的环境条件调整其身体表现，而环境耐受范围可能有助于划定一个物种的地理分布范围。飞行动物面临的一个常见环境挑战是高海拔地区空气密度的降低以及随之而来的升力产生效率的降低。作为一个物种，红头美洲鹫（Cathartes aura）栖息在海拔超过3000米的范围内，并且飞得更高，这就要求它们通过行为、生理或生物力学来适应27%的空气密度变化（从0.890千克/立方米到1.227千克/立方米）。我们预测，在高海拔飞行的鸟类会通过更高的飞行速度在行为上维持空气动力学升力表现，而不是增加功率输出或局部表型适应。我们使用三维摄像技术追踪在三个海拔高度飞行的红头美洲鹫，数据支持了空速中位数与空气密度之间假设的负相关关系。此外，水平速度与下沉速度的比率以及拍打行为均不随空气密度而变化。
