捕食风险对高原鼠兔食物大小选择的影响

INFLUENCE OF PREDATION RISK ON SELECTION OF FOOD SIZES FOR PLATEAU PIKAS

文章报道了捕食风险条件下高原鼠兔对食物大小选择的格局。在实验箱中放置艾虎以改变捕食风险水平 ,食物按体积大小分为 4种食物项目 ,并测定各项目摄入率和取食单个食物项目的进食时间 ,结果表明 ,摄入率与进食时间依食物项目体积的增大而增加。将大食物与小食物项目配对并供高原鼠兔选择时 ,食物项目的利用率视环境状况而不同。捕食风险处理中 ,小食物利用率依其进食时间的减少而增加 ,其程度与所配对的食物项目的摄入率和进食时间有关。在捕食风险的作用下 ,高原鼠兔的食物选择格局反映了能量摄取与风险避免间的权衡。

The patterns of selection of food sizes for plateau pikas under predation risk circumstances were demonstrated. Risk of predation was manipulated by introducing predator( Mustela eversmnni ) to experimental box in the laboratory. Food items were divided into four types based on their sizes. Intake rates and time spent on handling individual of food items were measured. The results show both of them significantly increase as sizes of food increase(F 3,45 =3 45, P <0 01; F 3,59 = 6 45, P <0 01). When we match the largest food item with other smaller food items respectively and present matched food items to plateau pikas, the patterns of selection for food items change as the current environment change. Under risky environment, rates of use for smaller food items which are lower intake rates and are beneficial to defend predator increase with decrease in sizes of the food (F 1,55 =6 81, P <0 05), reflecting the trade off between gaining energy and avoiding risk of predation These results suggest that the predicate of optimal diet theory is not expected when plateau pikas feed under risky circumstance.