Data_Sheet_2_Cognitive Performance of Wild Eastern Gray Squirrels (Sciurus carolinensis) in Rural and Urban, Native, and Non-native Environments.pdf

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.

提升的认知能力已被证明能够赋予某些物种适应新环境的优势，从而促进其在新环境中的定居。然而，这种提升的成因仍然扑朔迷离。提升的认知能力可能是在定居过程中，对新环境的适应性反应而发生的适应现象，或者，这种‘提升’可能仅仅是物种特性的反映。基于先前的研究发现，在东部灰松鼠（Sciurus carolinensis）中存在‘提升’的认知能力（即，在解决新型食物提取问题或‘创新’上的成功率更高），东部灰松鼠作为一种成功的哺乳动物入侵者和城市居民，我们采用种内比较范式来探究其‘提升’的认知能力的成因。我们进行了一项实地研究，比较了在本土（美国）和非本土环境（英国）中居住的、生活在乡村和城市栖息地的自由放养松鼠的认知表现。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）上的表现，一个针对困难问题的运动记忆回忆测试，以及一项空间学习任务。我们发现，在大多数衡量指标上，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）在第一次访问困难问题时，成功率高于非本土城市松鼠；（2）在延长一段时间后，对于困难问题的回忆延迟时间高于非本土乡村松鼠；（3）在遇到相同的困难问题时，能够进行学习。这些结果表明，先前报道的‘提升’表现可能是一种普遍特性，因此，是一种预适应表型特征，能够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轻微的变化。