Manicom Carryn, Schwarzkopf Lin, Alford Ross A, Schoener Thomas W
School of Marine and Tropical Biology, James Cook University, Townsville, Queensland 4811, Australia.
Proc Natl Acad Sci U S A. 2008 Sep 30;105(39):14903-7. doi: 10.1073/pnas.0807107105. Epub 2008 Sep 4.
Many animals modify their environments, apparently to reduce predation risk, but the success of such endeavors, and their impact on the density and distribution of populations, are rarely rigorously demonstrated. We staged a manipulative experiment to assess the effectiveness of self-made shelters by web spiders as protection from natural enemies. Scincid lizards were included or excluded from 21 replicated 200-m(2) plots, and spiders therein were classified as exposed or sheltered, depending on whether they were uncovered in their web or hidden in cocoons, leaves/debris, or burrows. We found that exposed spiders were greatly affected by the presence of predatory scincid lizards, whereas sheltered spiders were not. More specifically, lizards, which forage close to the ground, reduced the abundance of exposed spiders by two-thirds but had no effect on the abundance of sheltered spiders. Sheltered spiders were able to avoid predation and share space with lizards, suggesting that shelter construction is a mechanism for reducing predation risk and has important population consequences.
许多动物会改变它们的环境，显然是为了降低被捕食的风险，但这类行为的成效以及它们对种群密度和分布的影响，却很少得到严格的证明。我们进行了一项操纵性实验，以评估结网蜘蛛自制庇护所作为抵御天敌保护措施的有效性。在21个重复的200平方米样地中，要么放入石龙子蜥蜴，要么排除石龙子蜥蜴，样地中的蜘蛛则根据其蛛网是暴露在外还是隐藏在茧、树叶/碎片或洞穴中，分为暴露型或有庇护型。我们发现，暴露在外的蜘蛛受捕食性石龙子蜥蜴的影响很大，而有庇护的蜘蛛则不受影响。更具体地说，在地面附近觅食的蜥蜴使暴露在外的蜘蛛数量减少了三分之二，但对有庇护的蜘蛛数量没有影响。有庇护的蜘蛛能够避免被捕食，并与蜥蜴共享空间，这表明建造庇护所是一种降低捕食风险的机制，并且对种群有重要影响。
