Dissertation Research: Thirteen-Lined Ground Squirrel Antipredator Vigilance

9701137莱格尔研究动物在面临被捕食者吃掉的风险时的决策能力，可以揭示动物评估最佳权衡的复杂过程。最优权衡的一个简单例子是，一只动物面临两个相互冲突的选择，例如，觅食和扫描捕食者(反捕食者警觉)。觅食降低了饥饿的风险，而反捕食者的警惕降低了捕食的风险。动物无法在不招致另一种动物严重风险的情况下从其中一种动物那里获得最大利益。最理想的权衡是动物的选择是摄食和反捕食者警觉的联合最大值。决策是这项研究的基础框架。一个很常见的观察是，一个群体的规模增加，猎物的动物警觉性降低。这种警觉性的下降可能会导致动物有更多的时间进食，并可能成为社会性进化的一股重要力量。虽然视觉障碍在许多被捕食动物的环境中是一个常见的背景变量，但这个变量还没有得到太多的实证研究。13只地松鼠是生活在大平原上的穴居啮齿动物。它们被鸟类、陆生哺乳动物和蛇等爬行动物捕食。研究表明，只有当它们的远距离(大于20米)、横向视野被遮挡时，13只线沙鼠才能提高它们对捕食者的警惕。考虑到有多少动物捕食这些地松鼠，当它们的头顶视线被遮挡时，它们没有提高警惕的反应是相当令人惊讶的。为了测试关于反捕食者警觉和视觉障碍的假设，13只衬里的地松鼠被允许在有机玻璃盒子里进食，这些盒子以不同的方式遮挡松鼠充满的视野，并检测到即将到来的威胁。这是一项重要的测试，因为地面松鼠的反捕食者警觉行为表明，它们不认为某些位置的视觉障碍是重要的。因此，即使不提高它们的警觉性，地松鼠也应该能够检测到捕食者的攻击，因为在没有视觉障碍的情况下，它们的头顶上有视觉障碍。

9701137 Leger Studies of the decision-making capabilities of animals while they are under the risk of being eaten by predators can reveal the complex process by which animals evaluate optimal trade-offs. A simple example of an optimal trade-off is where an animal is faced with two conflicting choices, e.g., foraging versus scanning for predators (antipredator vigilance). Foraging reduces starvation risk while antipredator vigilance reduces predation risk. The animal is unable to maximize the benefit from one without incurring serious risk from the other. An optimal trade-off is where the animal's choice is the joint maximum of both feeding and antipredator vigilance. Decision-making is the framework within which this research is based. A very common observation is that a group size increases, prey animal vigilance decreases. This decrease in vigilance could result in the animal having more time to feed and could be a significant force in the evolution of sociality. Although visual obstruction is a common contextual variable in many prey animals' environment, this variable has not been given much empirical attention. Thirteen-lined ground squirrels are burrowing rodents that occur across the Great Plains. They are preyed upon by birds, terrestrial mammals, and reptiles such as snakes. It has been shown that thirteen-lined ground squirrels increase their antipredator vigilance only when their long-range (greater than 20m), lateral field of view is obstructed. Considering how many animals prey upon these ground squirrels, it is quite surprising that they do not react with increased vigilance when their 'overhead' view is obstructed. To test hypotheses about antipredator vigilance and visual obstruction, thirteen-lined ground squirrels are allowed to feed inside plexiglass boxes that differentially obstruct the squirrels' filled of view, and detect the approaching threat. This is an important test since ground squirrel antipredator vigilance behavior indicates that they do not co nsider certain positions of visual obstruction to be important. Therefore, even without increasing their vigilance, ground squirrels should be able to detect predator attacks with 'overhead' visual obstruction as when there is no visual obstruction.