Kramer DL, Bonenfant M
Department of Biology, McGill University
Anim Behav. 1997 Aug;54(2):289-95. doi: 10.1006/anbe.1996.0360.
How close should an animal allow a potential predator to approach before fleeing to a refuge? Fleeing too soon wastes time and energy that could be spent on other important activities, but fleeing too late is potentially lethal. A model to predict flight initiation distance was developed, based on the assumption that animals would flee at a distance that allows them to reach the refuge ahead of the predator by some margin of safety. This model predicts that (1) flight initiation distance should increase with distance from the refuge (which has been supported by studies on several species) and (2) the rate of increase of flight initiation distance with distance from a refuge should be higher when the refuge is between the predator and prey (prey runs towards the predator) than when the prey is between the predator and the refuge (prey runs away from the predator). Prediction 2 was tested by approaching juvenile woodchucks, Marmota monaxalong an imaginary line between the animal and its burrow entrance and measuring the distance between the observer and the animal at the moment it started its flight. As predicted, the rate of increase in flight initiation distance was higher when the burrow was between the observer and the woodchuck than when the woodchuck was between the observer and the burrow. The slopes were appropriate for predators with pursuit speeds about twice the escape speed of the woodchucks. The difference between the slopes was 1.78 m flight distance/m distance to refuge, close to the value of 2 m flight distance/m distance to refuge predicted by the model. The intercept indicated that woodchucks allowed a margin of safety of about 7.6 m. The model permits quantitative evaluation of the principal elements of flexible escape decisions of animals and provides a measure of how predation risk increases the cost of space use in relation to distance from a refuge.
在逃向避难所之前，动物应允许潜在捕食者靠近到多近的距离呢？过早逃离会浪费本可用于其他重要活动的时间和精力，但过晚逃离则可能致命。基于动物会在能让它们比捕食者提前一段安全距离到达避难所的距离处逃离这一假设，开发了一个预测逃跑起始距离的模型。该模型预测：（1）逃跑起始距离应随着与避难所距离的增加而增大（这已得到对多个物种研究的支持）；（2）当避难所在捕食者和猎物之间（猎物朝着捕食者跑去）时，逃跑起始距离随与避难所距离的增加速率应高于当猎物在捕食者和避难所之间（猎物远离捕食者）时的情况。通过沿着幼年土拨鼠（Marmota monax）与其洞穴入口之间的一条假想线接近它们，并测量动物开始逃跑时观察者与动物之间的距离，对预测2进行了测试。正如预测的那样，当洞穴在观察者和土拨鼠之间时，逃跑起始距离的增加速率高于当土拨鼠在观察者和洞穴之间时的情况。这些斜率对于追捕速度约为土拨鼠逃跑速度两倍的捕食者来说是合适的。斜率之间的差异为1.78米逃跑距离/米到避难所的距离，接近模型预测的2米逃跑距离/米到避难所的距离的值。截距表明土拨鼠留出了约7.6米的安全距离。该模型允许对动物灵活逃跑决策的主要要素进行定量评估，并提供了一种衡量捕食风险如何相对于与避难所的距离增加空间使用成本的方法。
