Rayor LS, Uetz GW
Department of Biological Sciences, University of Cincinnati
Anim Behav. 2000 Jun;59(6):1251-1259. doi: 10.1006/anbe.2000.1427.
Colonial orb-weaving spiders provide insight into the proximate mechanisms by which social animals space themselves within a group. We examined mechanisms for the temporal patterns of web building that determine individual positions in Metepeira incrassata (Araneidae) colonies. The spiders display a characteristic age-related sequence of daily web building, with larger spiders completing their webs significantly earlier than smaller ones. We used data on behavioural interactions, web building, prey capture and predator attacks to evaluate four hypotheses. (1) Larger spiders are better competitors and pre-empt optimal spatial positions. (2) Smaller spiders reduce competition with larger individuals by building webs later. (3) Prey captured by different size classes is available at different times. (4) Differential predation risk determines web-building times. Large individuals dominated behavioural interactions. Disturbances by larger spiders during web construction significantly delayed the completion of smaller individuals' webs and precipitated movements to new web sites. One prediction of the first hypothesis, that spatial needs translate into earlier building, was confirmed by significantly earlier web building by mature females with egg sacs (which are unable to move their egg sacs) compared with same-sized females without eggs (which can change locations freely). Experiments to determine whether the presence of large spiders inhibited the web building of smaller individuals were equivocal. Prey availability and risk of predation are not factors affecting web-building patterns. Sequential web building appears to be a result of both larger spiders competing to pre-empt space from one another and smaller individuals attempting to reduce conflict during web construction. Sequential web building is a proximate mechanism that influences spacing among colonial orb-weaving spiders and helps shape the typical hierarchical size distribution of spiders within the colony. Similar spacing mechanisms may be seen in colonial birds and marine invertebrates. Copyright 2000 The Association for the Study of Animal Behaviour.
群居圆蛛为研究群居动物在群体中如何进行空间分布的近因机制提供了线索。我们研究了决定厚胸梅塔蛛（圆蛛科）群体中个体位置的织网时间模式的机制。这些蜘蛛展现出一种与年龄相关的每日织网特征序列，体型较大的蜘蛛比体型较小的蜘蛛显著更早完成织网。我们利用行为互动、织网、猎物捕获和捕食者攻击的数据来评估四个假说。（1）体型较大的蜘蛛是更好的竞争者，会抢占最佳空间位置。（2）体型较小的蜘蛛通过延迟织网来减少与体型较大个体的竞争。（3）不同体型等级的蜘蛛捕获的猎物在不同时间可得。（4）不同的被捕食风险决定织网时间。大型个体主导行为互动。在织网过程中，体型较大的蜘蛛造成的干扰显著延迟了体型较小个体的织网完成，并促使它们转移到新的织网地点。第一个假说的一个预测，即空间需求转化为更早织网，通过以下事实得到证实：与没有卵（可以自由改变位置）的同体型雌蛛相比，携带卵囊（无法移动其卵囊）的成熟雌蛛织网明显更早。关于大型蜘蛛的存在是否抑制小型个体织网的实验结果并不明确。猎物可获得性和被捕食风险不是影响织网模式的因素。顺序织网似乎是体型较大的蜘蛛相互竞争抢占空间以及体型较小的个体试图减少织网过程中的冲突这两者共同作用的结果。顺序织网是一种近因机制，它影响群居圆蛛之间的空间分布，并有助于形成群体内蜘蛛典型的等级大小分布。类似的空间分布机制可能在群居鸟类和海洋无脊椎动物中也能看到。版权所有2000动物行为研究协会。
