Hawkes Lucy A, Butler Patrick J, Frappell Peter B, Meir Jessica U, Milsom William K, Scott Graham R, Bishop Charles M
School of Biological Sciences, Bangor University, Bangor, Gwynedd, United Kingdom; University of Exeter, College of Life and Environmental Sciences, Penryn Campus, Penryn, Cornwall, United Kingdom.
School of Biosciences, University of Birmingham, Birmingham, United Kingdom.
PLoS One. 2014 Apr 7;9(4):e94015. doi: 10.1371/journal.pone.0094015. eCollection 2014.
While bar-headed geese are renowned for migration at high altitude over the Himalayas, previous work on captive birds suggested that these geese are unable to maintain rates of oxygen consumption while running in severely hypoxic conditions. To investigate this paradox, we re-examined the running performance and heart rates of bar-headed geese and barnacle geese (a low altitude species) during exercise in hypoxia. Bar-headed geese (n = 7) were able to run at maximum speeds (determined in normoxia) for 15 minutes in severe hypoxia (7% O2; simulating the hypoxia at 8500 m) with mean heart rates of 466±8 beats min-1. Barnacle geese (n = 10), on the other hand, were unable to complete similar trials in severe hypoxia and their mean heart rate (316 beats.min-1) was significantly lower than bar-headed geese. In bar-headed geese, partial pressures of oxygen and carbon dioxide in both arterial and mixed venous blood were significantly lower during hypoxia than normoxia, both at rest and while running. However, measurements of blood lactate in bar-headed geese suggested that anaerobic metabolism was not a major energy source during running in hypoxia. We combined these data with values taken from the literature to estimate (i) oxygen supply, using the Fick equation and (ii) oxygen demand using aerodynamic theory for bar-headed geese flying aerobically, and under their own power, at altitude. This analysis predicts that the maximum altitude at which geese can transport enough oxygen to fly without environmental assistance ranges from 6,800 m to 8,900 m altitude, depending on the parameters used in the model but that such flights should be rare.
斑头雁以在喜马拉雅山脉高空迁徙而闻名，但之前对圈养鸟类的研究表明，这些大雁在严重缺氧条件下奔跑时无法维持耗氧率。为了探究这一矛盾现象，我们重新研究了斑头雁和黑雁（一种低海拔物种）在缺氧环境中运动时的奔跑表现和心率。斑头雁（n = 7）能够在严重缺氧（7%氧气；模拟8500米处的缺氧环境）下以最大速度（在常氧条件下测定）奔跑15分钟，平均心率为466±8次/分钟。另一方面，黑雁（n = 10）在严重缺氧环境中无法完成类似试验，其平均心率（316次/分钟）显著低于斑头雁。在斑头雁中，无论是在休息还是奔跑时，缺氧期间动脉血和混合静脉血中的氧分压和二氧化碳分压均显著低于常氧状态。然而，斑头雁血液乳酸测量结果表明，在缺氧奔跑过程中无氧代谢并非主要能量来源。我们将这些数据与文献中的数值相结合，以估计：（i）使用菲克方程估算氧气供应，以及（ii）使用空气动力学理论估算斑头雁在高空有氧飞行且依靠自身动力时的氧气需求。该分析预测，根据模型中使用的参数，大雁能够在无需环境辅助的情况下运输足够氧气进行飞行的最大高度范围为海拔6800米至8900米，但这种飞行应该很少见。
