Danner Bradford J, Joern Anthony
School of Biological Sciences, University of Nebraska-Lincoln, Lincoln, NE 68588-0118, USA.
Oecologia. 2003 Nov;137(3):352-9. doi: 10.1007/s00442-003-1362-9. Epub 2003 Aug 20.
In response to increased exposure to predators when searching for food, many prey increase the frequency of antipredator behaviors, potentially reducing foraging rate and food intake. Such direct, nonlethal interactions between predators and prey resulting in reduced food intake can indirectly influence lifecycle development through effects on growth, developmental rate, and survival. We investigated the general hypothesis that individual performance of a herbivorous insect can be negatively affected when exposed to nonlethal predation risk, and that the response can be mediated by food quality. This hypothesis was tested using the common rangeland grasshopper Ageneotettix deorum with and without exposure to common wolf spider predators (Lycosidae, Schizocosa spp.) on both untreated natural and fertilized vegetation. All spiders were rendered temporarily incapable of direct feeding by restricting function of the chelicerae with beeswax. Detectable responses by grasshoppers to spiders indicate indirect consequences for lifecycle development. Grasshopper performance was measured as hind femur growth, duration of nymphal lifecycle stages, and survivorship in a caged field experiment conducted over 2 years. Grasshoppers developed faster and grew 3-5% larger when allowed to forage on fertilized vegetation in the absence of risk from a spider predator. Failure-time analysis illustrated enhanced survival probability in response to elevated food quality and the negative effects of grasshopper susceptibility to nonlethal predation risk. Performance on food of relatively low, ambient quality with no predation risk equaled that of grasshoppers caged with high quality vegetation in the presence of a modified spider. Increased resource quality can clearly moderate the negative life history responses caused by the behavioral modification of grasshoppers when exposed to spider predation risk, a compensatory response.
在寻找食物时，由于接触捕食者的机会增加，许多猎物会增加反捕食行为的频率，这可能会降低觅食率和食物摄入量。捕食者与猎物之间这种直接的、非致命的相互作用导致食物摄入量减少，进而可能通过影响生长、发育速度和存活率间接影响生命周期的发展。我们研究了一个普遍的假设，即食草昆虫个体在面临非致命捕食风险时，其表现可能会受到负面影响，并且这种反应可能由食物质量介导。我们使用常见的草原蝗虫Ageneotettix deorum在未处理的天然植被和施肥植被上进行实验，分别设置有和没有接触常见狼蛛捕食者（狼蛛科，裂腹蛛属）的情况来验证这一假设。通过用蜂蜡限制螯肢的功能，使所有蜘蛛暂时无法直接进食。蝗虫对蜘蛛的可检测反应表明了对生命周期发展的间接影响。在一项为期两年的笼养田间实验中，通过测量蝗虫后股骨的生长、若虫生命周期阶段的持续时间和存活率来衡量蝗虫的表现。当蝗虫在没有蜘蛛捕食者风险的情况下在施肥植被上觅食时，它们发育得更快，体型增长了3 - 5%。失效时间分析表明，随着食物质量的提高，蝗虫的生存概率增加，同时也表明了蝗虫对非致命捕食风险的易感性所带来的负面影响。在没有捕食风险的情况下，处于相对低质量、自然环境质量食物上的蝗虫表现与在有改良蜘蛛存在的情况下处于高质量植被笼中的蝗虫表现相当。资源质量的提高显然可以缓解蝗虫在面临蜘蛛捕食风险时因行为改变而导致的负面生活史反应，这是一种补偿性反应。
