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首页> 外文期刊>Oecologia >Grazing in heterogeneous environments: infra- and supra-parasite distributions determine herbivore grazing decisions
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Grazing in heterogeneous environments: infra- and supra-parasite distributions determine herbivore grazing decisions

机译：在异质环境中放牧：亚寄生虫和超寄生虫的分布决定了草食动物的放牧决策

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We tested the hypothesis that the infra-gastrointestinal parasite population of herbivores affects their grazing behaviour in relation to the supra-parasite population of parasites in the environment. Our first objective was to create a naturally heterogeneous sward structure of gaps and tussocks using a continuous grazing scheme. We then demonstrate that a nutrition vs. parasitism grazing trade-off occurs within that sward structure and that infra-gastrointestinal parasite populations affect the grazing decisions of herbivores faced with the trade-off. A pool of 50 naturally parasitised female Soay sheep and their lambs were used to create a heterogeneous tall, faeces-contaminated tussock/short, non-contaminated gap sward structure in a 1-ha experimental plot. Tussocks offered approximately 1.5 times greater forage intake but contained 5.5 times the number of strongyle parasites compared to the gaps. Following a 10-week period in which the heterogeneous sward structure was created, two 5-day periods of observations of sward structure selection (i.e. gap vs. tussock) were carried out. Twenty female Soay lambs were divided into two groups of ten (balanced for live-weight) immediately prior to the start of the observation period. One of the groups of lambs was treated with an anthelmintic drench before the start of the second observation period creating two levels of parasitism (high and low). On each observation day 5-min focal observations were carried out on each animal at least twice a day, during which time the number of bites taken from gaps and tussocks were recorded along with the number of steps. During the first period of observations, all animals rejected the relatively tall, faeces-contaminated tussocks for grazing to a similar extent and had similar bite and step rates. During the second period of observations all animals showed reduced rejection of the tussocks relative to the first week, however, animals with a reduced parasite population showed a greater reduction in rejection as compare to the highly parasitised animals. We conclude that the infra- and supra-distributions of parasites within herbivore hosts and the environment greatly impact on herbivore grazing behaviour and foraging decisions and thus the structure and heterogeneity of grazed ecosystems.
机译：我们检验了以下假设：草食动物的下胃肠道寄生虫种群相对于环境中的寄生虫超寄生虫种群影响其放牧行为。我们的第一个目标是使用连续放牧方案创建缝隙和丛的天然异质草地结构。然后，我们证明了在草皮结构中发生了营养与寄生性放牧的权衡，并且肠下寄生虫种群影响了面临权衡的食草动物的放牧决策。在1公顷的试验田中，使用50只自然寄生的雌性Soay绵羊及其羔羊的池来创建异质的，高大便，受粪便污染的丛状/短而无污染的缝隙草皮结构。 s提供的草料摄入量大约是空腹的1.5倍，但其扁桃体寄生虫的数量是空腹的5.5倍。在创建异类草皮结构的10周期间之后，进行了两个5天的观察，观察草皮结构的选择（即缝隙与草丛）。在观察期即将开始之前，将20只雌性Soay羔羊分为两组，每组十只（以活重平衡）。在第二个观察期开始之前，对一组羔羊进行了驱虫药浸湿处理，产生了两个水平的寄生虫（高和低）。在每个观察日，每天至少两次对每只动物进行5分钟的局部观察，在此期间，记录从间隙和丛中被咬的次数以及步数。在观察的第一阶段，所有动物都拒绝了相对较高，被粪便污染的草丛，因为它们的放牧程度相似，并且叮咬和步速相似。在观察的第二阶段，与第一周相比，所有动物对的排斥反应均降低，但是，与高度寄生虫的动物相比，寄生虫种群减少的动物的排斥反应降低更大。我们得出的结论是，食草动物宿主和环境中寄生虫的分布在地上和上方，这极大地影响了草食动物的放牧行为和觅食决策，进而影响了放牧生态系统的结构和异质性。

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