Beliniak Agata, Gryz Jakub, Klich Daniel, Łopucki Rafał, Sadok Ilona, Ożga Kinga, Jasińska Karolina D, Ścibior Agnieszka, Gołębiowska Dorota, Krauze-Gryz Dagny
Department of Forest Zoology and Wildlife Management, Warsaw University of Life Sciences, Warsaw, Poland.
Department of Forest Ecology, Forest Research Institute, Sękocin Stary, Raszyn, Poland.
PLoS One. 2024 May 3;19(5):e0302933. doi: 10.1371/journal.pone.0302933. eCollection 2024.
Animals in urban areas often encounter novel and potentially stressful conditions. It is important to understand how wildlife cope with anthropogenic disturbance. To investigate this specific adaptation we live-trapped squirrels in two study sites in Warsaw: a forest reserve and an urban park and we estimated stress responses at three levels: long-term and medium-term stress (the level of stress hormones, i.e. cortisol and cortisone concentrations, in hair and feces) and acute reaction to human-induced stress (measured during handling with the aid of the three indices: breath rate, struggle rate, and vocalization). According to GLMM models no difference in the stress hormones level was found between the two populations. The only differences in cortisol concentrations clearly depended on the season, i.e. being higher in autumn and winter comparying to other seasons. There was no influence of sex, or reproductive status on stress hormones. Forest squirrels had significantly higher breath rates, suggesting they were more stressed by handling. There was no difference in the struggle rate between study areas, this index was mostly affected by season (i.e. being highest in winter). First-trapped squirrels vocalized less than during the subsequent trappings. Assumingly, during the first, and more stressful trapping, squirrels used 'freezing' and/or little vocalization, while during next captures they used alarm calls to warn conspecifics. Overall, we showed that the two squirrel populations differed only in terms of their breath rate. This suggests that they did not differ in medium-term and long-term stress in general, but they can differ in acute response to handling. This also suggests that both populations were similarly affected by environmental factors. The lack of clear effects may also be due to population heterogeneity. Thus, in order to assess the effects of anthropogenic stressors a broader range of indicators and diverse analytical methods, including behavioral analyses, should be employed.
城市地区的动物经常会遇到新奇且可能带来压力的环境。了解野生动物如何应对人为干扰非常重要。为了研究这种特定的适应性，我们在华沙的两个研究地点用活套捕捉松鼠：一个森林保护区和一个城市公园，我们在三个层面评估应激反应：长期和中期应激（毛发和粪便中应激激素的水平，即皮质醇和可的松的浓度）以及对人为诱导应激的急性反应（在处理过程中借助三个指标进行测量：呼吸频率、挣扎率和发声情况）。根据广义线性混合模型，在两个种群之间未发现应激激素水平存在差异。皮质醇浓度的唯一差异明显取决于季节，即与其他季节相比，秋季和冬季的皮质醇浓度更高。性别或生殖状态对应激激素没有影响。森林松鼠的呼吸频率明显更高，这表明它们在处理过程中受到的压力更大。研究区域之间的挣扎率没有差异，该指标主要受季节影响（即在冬季最高）。首次捕获的松鼠发声比后续捕获时少。据推测，在第一次且压力更大的捕获过程中，松鼠会采用“静止不动”和/或很少发声的方式，而在接下来的捕获中，它们会使用警报叫声来警告同类。总体而言，我们发现这两个松鼠种群仅在呼吸频率方面存在差异。这表明它们在中期和长期应激方面总体上没有差异，但在对处理的急性反应方面可能存在差异。这也表明这两个种群受到环境因素的影响类似。缺乏明显影响也可能是由于种群异质性。因此，为了评估人为应激源的影响，应该采用更广泛的指标和多样的分析方法，包括行为分析。
