关键词: 高原鼠兔, 捕食风险, 食物选择

Abstract: 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.

Key words: Plateau pikas (Ochotona curzonia), Risk of predation, Selection of food