Swaddle John P, Diehl Tessa R, Taylor Capwell E, Fanaee Aaron S, Benson Jessica L, Huckstep Neil R, Cristol Daniel A
Biology Department, College of William and Mary, Institute for Integrative Bird Behavior Studies, Williamsburg, VA 23187-8795, USA.
Biological Sciences, Virginia Tech, 1405 Perry Street, Blacksburg, VA 24061, USA.
Curr Zool. 2017 Apr;63(2):213-219. doi: 10.1093/cz/zox007. Epub 2017 Feb 10.
Environmental stressors can negatively affect avian cognitive abilities, potentially reducing fitness, for example by altering response to predators, display to mates, or memory of locations of food. We expand on current knowledge by investigating the effects of dietary mercury, a ubiquitous environmental pollutant and known neurotoxin, on avian cognition. Zebra finches were dosed for their entire lives with sub-lethal levels of mercury, at the environmentally relevant dose of 1.2 parts per million. In our first study, we compared the dosed birds with controls of the same age using tests of three cognitive abilities: spatial memory, inhibitory control, and color association. In the spatial memory assay, birds were tested on their ability to learn and remember the location of hidden food in their cage. The inhibitory control assay measured their ability to ignore visible but inaccessible food in favor of a learned behavior that provided the same reward. Finally, the color association task tested each bird's ability to associate a specific color with the presence of hidden food. Dietary mercury negatively affected spatial memory ability but not inhibitory control or color association. Our second study focused on three behavioral assays not tied to a specific skill or problem-solving: activity level, neophobia, and social dominance. Zebra finches exposed to dietary mercury throughout their lives were subordinate to, and more active than, control birds. We found no evidence that mercury exposure influenced our metric of neophobia. Together, these results suggest that sub-lethal exposure to environmental mercury selectively harms neurological pathways that control different cognitive abilities, with complex effects on behavior and fitness.
环境压力源会对鸟类的认知能力产生负面影响，可能会降低其适应性，例如通过改变对捕食者的反应、对配偶的展示或对食物位置的记忆。我们通过研究膳食汞（一种普遍存在的环境污染物和已知的神经毒素）对鸟类认知的影响，来扩展当前的知识。斑胸草雀在其一生中都被施以亚致死剂量的汞，剂量为百万分之一百二十，这是与环境相关的剂量。在我们的第一项研究中，我们使用三种认知能力测试，将喂食汞的鸟类与相同年龄的对照组进行比较：空间记忆、抑制控制和颜色联想。在空间记忆测定中，测试鸟类学习和记住笼子里隐藏食物位置的能力。抑制控制测定衡量它们忽略可见但无法获取的食物，而倾向于一种能提供相同奖励的习得行为的能力。最后，颜色联想任务测试每只鸟将特定颜色与隐藏食物的存在联系起来的能力。膳食汞对空间记忆能力有负面影响，但对抑制控制或颜色联想没有影响。我们的第二项研究集中在三种与特定技能或解决问题无关的行为测定上：活动水平、新事物恐惧症和社会优势地位。终生暴露于膳食汞的斑胸草雀比对照鸟地位低且更活跃。我们没有发现证据表明汞暴露会影响我们衡量新事物恐惧症的指标。总之，这些结果表明，亚致死剂量的环境汞暴露会选择性地损害控制不同认知能力的神经通路，对行为和适应性产生复杂影响。
