School of Biological Sciences, Monash University, Clayton, VIC, 3800, Australia.
J Therm Biol. 2023 Oct;117:103707. doi: 10.1016/j.jtherbio.2023.103707. Epub 2023 Sep 22.
How the accelerating pace of global warming will affect animal populations depends on the effects of increasing temperature across the life cycle. Developing young are sensitive to environmental challenges, often with life-long consequences, but the risks of climate warming during this period are insufficiently understood. This may be due to limited insight into physiological sensitivity and the temperatures that represent a thermal challenge for young. Here we examined the physiological and behavioural effects of increasing temperatures by measuring metabolic rate, water loss, and heat dissipation behaviours between 25-45 °C in nestlings of a small free-living songbird of temperate SE-Australia, the superb fairy-wren. We found a high and relatively narrow thermoneutral zone from 33.1 to 42.3 °C, with metabolic rate increasing and all nestlings panting above this range. Evaporative water loss sharply increased above 33.5 °C; at the same temperature, nestlings changed their posture (extended their wings) to facilitate passive heat loss. However, at all temperatures measured, water loss was insufficient to dissipate metabolically produced heat, indicating poor cooling capabilities, which persisted even when individuals were panting. While nestlings are relatively tolerant to higher temperatures, with no evidence for hyperthermia at temperatures below 42 °C, they are at a high risk of dehydration even at lower temperatures, with limited ability to mitigate this. Thus, climate warming is likely to elevate the risk dehydration, which is concerning, since it is accompanied by drier conditions.
全球变暖的加速步伐将如何影响动物种群取决于整个生命周期中温度升高的影响。发育中的幼崽对环境挑战很敏感，通常会产生终身影响，但气候变暖在这一时期的风险还没有得到充分的理解。这可能是由于对生理敏感性和代表幼崽热挑战的温度的有限了解。在这里，我们通过测量代谢率、失水率和在 25-45°C 之间的散热行为，研究了温度升高对澳大利亚东南部一种小型自由生活的鸣禽——华美细尾鹩莺雏鸟的生理和行为影响。我们发现，从 33.1 到 42.3°C 的范围相对较窄，代谢率较高，所有雏鸟在这个范围内都开始喘气。在 33.5°C 以上，蒸发失水急剧增加；在同一温度下，雏鸟改变姿势（伸展翅膀）以促进被动散热。然而，在测量的所有温度下，失水不足以散发代谢产生的热量，表明散热能力较差，即使个体在喘气时也持续存在。虽然雏鸟对较高的温度相对耐受，在低于 42°C 的温度下没有证据表明体温过高，但即使在较低的温度下，它们也面临着高度脱水的风险，而且缓解这种风险的能力有限。因此，气候变暖可能会增加脱水的风险，这令人担忧，因为它伴随着更干燥的条件。
