Tabh Joshua K R, Mastromonaco Gabriela F, Burness Gary
Environmental and Life Sciences Graduate Program, Trent University, Peterborough, ON, K9L 0G2, Canada.
Department of Wildlife and Science, Toronto Zoo, Scarborough, ON, M1B 5K7, Canada.
Oecologia. 2022 Mar;198(3):663-677. doi: 10.1007/s00442-022-05120-z. Epub 2022 Feb 9.
Urbanisation can alter local microclimates, thus creating new thermal challenges for resident species. However, urban environments also present residents with frequent, novel stressors (e.g., noise, human interaction) which may demand investment in costly, self-preserving responses (e.g., the fight-or-flight response). One way that urban residents might cope with this combination of demands is by using regional heterothermy to reduce costs of thermoregulation during the stress response. In this study, we used black-capped chickadees (n = 9; n = 10) to test whether known heterothermic responses to stress exposure (here, at the bare skin around the eye): (1) varied consistently among individuals (i.e., were repeatable), and (2) were most pronounced among urban individuals compared with rural individuals. Further, to gather evidence for selection on stress-induced heterothermic responses in urban settings, we tested: (3) whether repeatability of this response was lower among birds sampled from urban environments compared with those sampled from rural environments. For the first time, we show that heterothermic responses to stress exposures (i.e. changes in body surface temperature) were highly repeatable across chronic time periods (R = 0.58) but not acute time periods (R = 0.13). However, we also show that these responses did not differ between urban and rural birds, nor were our repeatability estimates any lower in our urban sample. Thus, while regional heterothermy during stress exposure may provide energetic benefits to some, but not all, individuals, enhanced use of this response to cope with urban pressures appears unlikely in our study species.
城市化会改变当地的微气候，从而给当地物种带来新的热挑战。然而，城市环境也给居民带来频繁的、新出现的应激源（如噪音、人际互动），这可能需要投资于代价高昂的自我保护反应（如战斗或逃跑反应）。城市居民应对这种综合需求的一种方式可能是利用区域性异温性来降低应激反应期间的体温调节成本。在本研究中，我们使用黑头山雀（n = 9；n = 10）来测试已知的对应激暴露的异温反应（此处为眼睛周围的裸露皮肤）：（1）个体间是否一致变化（即是否具有重复性），以及（2）与农村个体相比，城市个体中的这种反应是否最为明显。此外，为了收集城市环境中对应激诱导的异温反应进行选择的证据，我们测试了：（3）与从农村环境中采样的鸟类相比，从城市环境中采样的鸟类中这种反应的重复性是否更低。我们首次表明，对应激暴露的异温反应（即体表温度变化）在慢性时间段内具有高度重复性（R = 0.58），但在急性时间段内并非如此（R = 0.13）。然而，我们也表明，这些反应在城市和农村鸟类之间没有差异，而且我们在城市样本中的重复性估计也没有更低。因此，虽然应激暴露期间的区域性异温性可能会给一些（但不是所有）个体带来能量益处，但在我们的研究物种中，增强利用这种反应来应对城市压力似乎不太可能。
