Behavioural choice and background matching facilitate camouflage in the European garden spider

Visual camouflage via background matching involves a variety of adaptive traits to maintain crypsis, including intraspecific color variation, behavioral choice of substrates, and color change. These non-mutually exclusive solutions frequently act together to conceal and deceive prey and enemies. Here, we combine field observations, image analysis, and laboratory experiments to investigate which processes drive camouflage in the garden cross spider (Araneus diadematus), a species with body coloration that varies in shades of brown. We demonstrate that A. diadematus does not change color significantly, at least within the same instar, when retained on substrates of different coloration. However, there is strong behavioral selection through active substrate choice across spiders for color-matching substrates (dead brown leaves over green leaves) when offered a choice under laboratory conditions. Similar background selection also apparently occurs in nature, where spiders were often observe..., We collected garden cross spiders (Araneus diadematus) and plant leaves (green and brown from host plants; brown from sympatric species) in the field for use in laboratory experiments. In the field study and colour change experiment, we quantified spider colour and camouflage from digital photographs using methods of image analysis and visual modelling. In the behavioural-choice experiment, we recorded spider preferences between green and brown leaves in binomial trials., # Behavioural choice and background matching facilitate camouflage in the European garden spider

https://doi.org/10.5061/dryad.6wwpzgn9j

Authors: Yuri Fanchini Messas; Rafael Campos Duarte; João Vasconcellos-Neto; and Martin Stevens

Contact: Yuri Fanchini Messas, [[e-mail]](mailto:[e-mail])

## Abstract

Here, we used image analysis and visual modelling of an avian predator (the Eurasian Blue Tit *Cyanistes caeruleus*) to assess the color variation and camouflage of European garden spiders (*Araneus diadematus*) inhabiting shrub vegetation in southwest UK. We predicted that spiders would be more effectively camouflaged on their chosen resting substrates (brown host leaves) compared to other substrates available in the surrounding environment. Additionally, we hypothesize that *A. diadematus* background matching relies on phenotypic plasticity in spiders’ body coloration, with a fine-scale individual resemblance to the color of the host leaf, or of behavioral s...,

通过背景匹配实现的视觉伪装，依赖于一系列用以维持隐蔽性的适应性特征，包括种内体色变异、生境底物的行为选择以及体色变化。这些互不排斥的策略通常协同发挥作用，以实现对猎物与天敌的隐蔽与欺骗。本研究结合野外观察、图像分析与室内实验，旨在探究驱动十字园蛛（*Araneus diadematus*，该物种种体体色呈深浅不一的棕色）伪装效果的关键机制。我们发现，当十字园蛛被置于不同体色的底物上时，其体色并不会发生显著变化——至少在同一龄期内是如此。但在实验室的选择实验中，蜘蛛会主动选择与自身体色匹配的底物（枯棕色叶片相较于绿色叶片），表现出强烈的底物行为选择偏好。类似的背景选择现象在野外也同样存在，野外观察中蜘蛛常被发现……

我们野外采集了十字园蛛（*Araneus diadematus*）与植物叶片（包括寄主植物的绿色、棕色叶片，以及同域分布物种的棕色叶片）用于室内实验。在野外研究与体色变化实验中，我们通过图像分析与视觉建模方法，对数码照片中的蜘蛛体色与伪装效果进行量化分析。在行为选择实验中，我们采用二项选择试验记录蜘蛛对绿色与棕色叶片的偏好。

# 行为选择与背景匹配助力欧洲十字园蛛的视觉伪装

数据集DOI：https://doi.org/10.5061/dryad.6wwpzgn9j
作者：Yuri Fanchini Messas; Rafael Campos Duarte; João Vasconcellos-Neto; Martin Stevens
联系方式：Yuri Fanchini Messas, [[e-mail]](mailto:[e-mail])

**摘要**：本研究通过图像分析与针对鸟类捕食者（欧亚蓝山雀*Cyanistes caeruleus*）的视觉建模方法，评估了栖息于英国西南部灌丛植被中的欧洲十字园蛛（*Araneus diadematus*）的体色变异与伪装效果。我们提出假设：相较于周围环境中的其他底物，蜘蛛在其主动选择的栖息底物（棕色寄主叶片）上会拥有更优异的伪装效果。此外，我们推测十字园蛛的背景匹配能力依赖于其体色的表型可塑性，即个体体色可与寄主叶片的颜色实现精细匹配，或是通过行为……