觅食时间和食物可利用性对波尔山羊觅食行为的作用格局

Effects of Foraging Time Restriction on the Foraging Behavior of Boergoats

在人工种植的多年生黑麦草草地条件下,采用重复的2×2析因实验设计,以植被高度3.0 cm(-H)和6.0 cm(+H)为食物可利用性因子,以觅食时间限制(夜间禁牧,-T)和无觅食时间限制(昼夜放牧,+T)为觅食时间因子,测定觅食时间和食物可利用性对波尔山羊觅食行为、食物摄入量和食物消化率的独立作用及其交互作用.研究结果表明,在排除食物可利用因子的条件下,觅食时间限制处理个体的觅食回合极显著地降低(P<0.01),觅食时间亦极显著地延长(P<0.01);而日总觅食时间则较无觅食时间限制处理个体显著地减少(P<0.01).觅食时间限制处理个体以较大口量觅食,能显著地提高其瞬时摄入率;而无觅食时间限制处理个体则不能使其瞬时摄入率最大化.觅食时间限制处理个体仅在+H条件下,能补偿其因每日觅食时间减少而损失的摄入量.反之,在-H条件下,觅食时间限制处理能降低其总的日摄入量.研究结果充分验证了本文提出的,在低矮植被,大型植食性哺乳动物的日摄入量依赖于其日觅食时间的假设.

Foraging behaviour,intake rate and diet digestibility of boergoats were measured on man-made ryegrass pastures in a replicated 2 × 2 factorial experiment. Overnight access to ryegrass pasture was varied（restricted overnight and continuous access）on two sward heights（ 6.0 and 3.0 cm）, represented high and low availability. Regardless of food availability,the time-restricted boergoats fed for all of the available grazing time by grazing for fewer,longer foraging bouts,but still had much shorter total daily gazing time than the time-unrestricted boergoats. In response to time grazing restriction, the boergoat had a significantly higher instantaneous rates of intake achieved mainly with larger bites. The time-unrestricted boergaots were not maximizing their short-term rate of intake, whilst grazing according to normal boergaots. The behavioural responses to time grazing restriction were able to counteract the reduction in daily grazing time only where food availability was high. In contrast ,on short swards time grazing restriction led to a reduction in total daily intake. The results from four experimental treatments generally supported the hypothesis that total daily grazing time is a key constrain on daily intake in lower sward.