捕食风险对不同饥饿状态下艾虎取食行为的影响

The effect of predation risk on the feeding behavior of the steppe polecat in different starvation conditions

在室内条件下,将大鵟作为艾虎的天敌动物,通过双通道选择实验确定6只成体艾虎在3个捕食风险水平和4种饥饿状态条件下的取食行为,探讨艾虎在取食过程中对饥饿风险与捕食风险的权衡策略。研究结果表明:在无捕食风险存在时,艾虎被剥夺食物0d和1d后对食物量不同的两个斑块中的取食量和利用频次均无明显不同(P>0.05),但对高食物量斑块的利用时间均明显高于低食物量斑块的(P<0.05),而艾虎被剥夺食物2d和3d后对高食物量斑块中的取食量和利用时间均明显高于低食物量斑块中的(P<0.05),但在利用频次上均无明显差异(P>0.05)。在面临低风险时,艾虎在4种饥饿状态下均只利用无天敌动物存在的低食物量斑块,而基本不利用有天敌动物存在的高食物量斑块。在面临高风险时,艾虎不得不利用有天敌动物存在的食物斑块,被剥夺食物0d时艾虎对无风险、无食物量斑块的利用时间基本相同于对高风险、有食物量斑块的利用时间(P>0.05),而被剥夺食物1d、2d和3d后艾虎对高风险、有食物量斑块的利用时间明显高于无风险、无食物量斑块的(P<0.05)。在相同风险条件下,随着饥饿程度增加,艾虎在斑块中的取食量均明显增加(P<0.05),而对斑块的利用时间和利用频次明显降低(P<0.05)。在相同的饥饿状态下,不同风险水平时,艾虎在斑块中的取食量无明显的差异(P>0.05),但在低风险和高风险时对斑块的利用时间和频次均明显低于无风险时的(P<0.05)。以上结果说明艾虎能够根据食物摄取率和自身的能量需求在捕食风险和饥饿风险之间做出权衡,当饥饿风险小于捕食风险时,艾虎趋于躲避捕食风险,当饥饿风险大于捕食风险时,艾虎趋于面对捕食风险,所采用的取食策略是减少活动时间和能量消耗,最大程度地提高单位时间内获得的能量。

In order to investigate the trade-off between the starvation risk and predation risk in the feeding process of the steppe polecat （Mustela eversmanni ） , the feeding behaviors of 6 adult steppe polecats in the patches with different food quantities were observed under three predation risks and four starvation levels by using two-choice test in the laboratory, with upland buzzard （Buteo hemilasius ） as predator. The results showed that under no predation risk, firstly , all of the polecats took equal food in different patches with same frequency whether they were starved for 0 or 1 day, but they spent longer feeding time in the patch with more food （ P 〈 0. 05 ） ; secondly, they spent more time and obtained more food in the patch with high quantity （ P 〈 0. 05 ）, but their feeding frequency was not different when they were deprived food for 2 or 3 days （ P 〉 0. 05 ）. When facing lower predation risks, all of the animals only got food from the patch with less food and no upland buzzard under 4 different starvation levels （P 〈 0. 05 ）. And when there were high risks, polecats had to use the food from the patch with an upland buzzard; they spent same time in two different patches under the no starvation condition,but spent longer time in the patch with food and upland buzzard than in the patch without food and enemy when starved for 1, 2 or 3 days （P 〈 0. 05 ）. It was also found that their food intake amount was proportional, but feeding time and frequency were inversely proportional to their starvation time, whatever the levels of the predation risk they facing （P 〈 0. 05 ）. Under the same starvation conditions, polecats took the same amount food in all of 3 predation risks, but compared to no predation risk, low and high predation risk made them decrease their active time and feeding frequency significantly （P 〈 0. 05）. These results indicated that the polecat could make a trade-off between the starvation risk and predation risk according to the need for energy. They were inclined to the risk-aversion when the starvation risk was lower than the predation risk and preferred to risk-proneness when the starvation risk was higher than the predation risk. It could be concluded that the feeding strategy of the polecat was to decrease the active time and energy consumption and get the largest net energy in unit time.