Pravosudov Vladimir V, Kitaysky Alexander S, Wingfield John C, Clayton Nicola S
Department of Psychology, University of California Davis, Young Hall, CA 95616-8519, USA.
Comp Biochem Physiol A Mol Integr Physiol. 2004 Jan;137(1):95-103. doi: 10.1016/s1095-6433(03)00264-2.
Birds respond to deterioration in environmental conditions by elevating their corticosterone levels, which can enhance their survival. It is less clear if animals constantly living in energetically challenging environment show similar increases in adrenocortical function. Previous work has demonstrated that under controlled conditions black-capped chickadees (Poecile atricapilla) from northern latitudes cache more food and perform better on spatial memory tasks than their southern conspecifics. As elevated levels of corticosterone have been shown previously to correlate with spatial memory performance in chickadees, this study aimed to investigate whether black-capped chickadees from northern latitudes have elevated baseline levels of corticosterone and/or a stronger adrenocortical stress response than their southern conspecifics, irrespective of their immediate environment. We found no differences between Alaskan and Colorado chickadees maintained under identical conditions for 3 months in either baseline levels of corticosterone or maximum levels of corticosterone achieved during the stress response. Baseline corticosterone levels were negatively correlated with relative body mass across both groups of birds. Our results suggest that the population differences in food catching behavior and spatial memory were not related to differences in corticosterone levels. We conclude that many reported population differences in baseline levels and in strength of adrenocortical stress response may often reflect differences in local environmental conditions rather than population-specific physiological traits.
鸟类通过提高其皮质酮水平来应对环境条件的恶化，这可以提高它们的生存能力。对于长期生活在能量需求较高环境中的动物，其肾上腺皮质功能是否会有类似的增强，目前尚不清楚。先前的研究表明，在受控条件下，来自北纬地区的黑顶山雀（Poecile atricapilla）比来自南方的同物种山雀储存更多食物，并且在空间记忆任务中表现更好。由于先前已表明皮质酮水平升高与山雀的空间记忆表现相关，因此本研究旨在调查来自北纬地区的黑顶山雀是否比来自南方的同物种山雀具有更高的皮质酮基线水平和/或更强的肾上腺皮质应激反应，而不考虑它们所处的直接环境。我们发现，在相同条件下饲养3个月的阿拉斯加山雀和科罗拉多山雀，在皮质酮基线水平或应激反应期间达到的皮质酮最高水平方面均无差异。两组鸟类的皮质酮基线水平均与相对体重呈负相关。我们的结果表明，在捕食行为和空间记忆方面的种群差异与皮质酮水平的差异无关。我们得出结论，许多报道的在基线水平和肾上腺皮质应激反应强度方面的种群差异，可能往往反映了当地环境条件的差异，而非特定种群的生理特征。
