Urbanization is a selective force that is known to drive changes in the population dynamics of wildlife. How animals adapt to changing environmental conditions is crucial to their survival in these environments. Relative brain size, or cranial capacity, is a known proxy of behavioral flexibility, and can be used to assess how well a species has adapted to a particular environment. We examined changes in cranial capacity in a time series of small mammal skulls collected from urban and rural populations in southwestern Pennsylvania. Skulls from urban populations were collected from Allegheny County, an area that experienced rapid urbanization over the past century, and skulls of rural populations from the Powdermill Nature Reserve of the Carnegie Museum, which has remained relatively unchanged forest over the same period. Our results show that Peromyscus leucopus and Microtus pennsylvanicus from urban populations had significantly greater cranial capacity than their rural counterparts, but the opposite was true for Eptesicus fuscus. We found no difference in relative cranial capacity across time in any of the small mammal species. Our results suggest that a larger cranial capacity is selected for in an urban environment and reinforces the hypothesis that behavioral flexibility is important for animals to adapt to novel environments.

中文翻译：

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在一个城市化的世纪中选择提高小型哺乳动物的颅骨能力

城市化是一种选择性力量，众所周知，它会推动野生动植物种群动态的变化。动物如何适应不断变化的环境条件对于它们在这些环境中的生存至关重要。大脑的相对大小或颅骨容量是行为灵活性的已知代表，可用于评估物种对特定环境的适应程度。我们检查了从宾夕法尼亚州西南部城市和农村地区收集的小型哺乳动物头骨的时间序列中颅骨容量的变化。来自城市人口的头骨来自上一个世纪以来经历了快速城市化的阿勒格尼县，以及来自卡内基博物馆的Powdermill自然保护区的农村人口的头骨，该林木在同期一直保持相对不变的森林。我们的结果表明来自城市人群的白带菌和隐孢子虫的颅骨能力明显高于农村人群，但深海疫菌则相反。我们发现，在任何小型哺乳动物物种中，相对颅骨容量随时间的变化均无差异。我们的结果表明，在城市环境中选择了较大的颅骨，并强化了行为灵活性对于动物适应新环境至关重要的假设。