Data_Sheet_1_Cognitive Performance of Wild Eastern Gray Squirrels (Sciurus carolinensis) in Rural and Urban, Native, and Non-native Environments.ZIP

Enhanced cognitive ability has been shown to impart fitness advantages to some species by facilitating establishment in new environments. However, the cause of such enhancement remains enigmatic. Enhanced cognitive ability may be an adaptation occurring during the establishment process in response to new environments or, alternatively, such ‘enhancement’ may merely reflect a species’ characteristic. Based on previous findings that have shown ‘enhanced’ cognitive ability (i.e., higher success rate in solving novel food-extraction problems or, ‘innovation’) in Eastern gray squirrels (Sciurus carolinensis), a successful mammalian invader and urban dweller, we used an intraspecific comparative paradigm to examine the cause of their ‘enhanced’ cognitive ability. We conducted a field study to compare cognitive performance of free-ranging squirrels residing in rural and urban habitats in native (United States) and non-native environments (United Kingdom). By using established tasks, we examined squirrels’ performance in easy and difficult, novel food-extraction problems (innovation), a motor memory recall test of the difficult problem, and a spatial learning task. We found that the four groups of squirrels showed comparable performance in most measures. However, we also found that the native urban squirrels showed: (1) higher success rate on the first visit for the difficult problem than the non-native urban squirrels; (2) some evidence for higher recall latency for the difficult problem after an extended period than the non-native rural squirrels; and (3) learning when encountering the same difficult problem. These results suggest that the previously reported ‘enhanced’ performance is likely to be a general characteristic and thus, a pre-adaptive phenotypic trait that brings fitness advantages to this species in a new environment. Despite this, some cognitive abilities in gray squirrels such as solving novel problems has undergone mild variation during the adaptive process in new environments.

增强的认知能力已被证实能够赋予某些物种适应新环境的适应性优势。然而，这种增强的成因仍然神秘莫测。增强的认知能力可能是物种在建立过程中对新环境响应而发生的适应性变化，或者，这种‘增强’可能仅仅反映了物种的固有特征。基于之前的研究成果，这些研究显示东部灰松鼠（Sciurus carolinensis）在解决新型食物提取问题（即创新）或‘创新’方面的成功率为‘增强’认知能力（即，在解决新型食物提取问题或‘创新’方面的成功率更高），作为一种成功的哺乳动物入侵者和城市居民，我们采用了一种物种内比较范式来检验它们‘增强’认知能力的成因。我们进行了一项现场研究，比较了在本土（美国）和非本土环境（英国）中居住的农村和城市栖息地的自由活动的松鼠的认知表现。通过使用既定任务，我们考察了松鼠在简单和困难的、新型食物提取问题（创新）中的表现，对困难问题的运动记忆回忆测试，以及空间学习任务。我们发现，在大多数指标上，四组松鼠的表现相当。然而，我们也发现，本土城市松鼠表现出：（1）在首次访问困难问题时比非本土城市松鼠的成功率更高；（2）在经过一段延长时期后，对困难问题的回忆潜伏期比非本土农村松鼠更长；以及（3）在遇到相同的困难问题时表现出学习行为。这些结果表明，先前报道的‘增强’表现可能是一种普遍特征，因此，是一种预适应性表型特征，为该物种在新环境中带来适应性优势。尽管如此，灰松鼠的一些认知能力，如解决新型问题，在新环境适应过程中经历了一定的轻微变化。