Data from: Active background choice facilitates crypsis in a tropical crab

Animals can evade predators in multiple ways, one of the most effective of which is to avoid detection in the first place. We know much about the evolution of color patterns that match the visual background to avoid detection (i.e., crypsis), yet we know surprisingly less about the specific behaviors that have co-evolved with these morphological traits to enhance or maintain crypsis. We here explore whether the match between body color and background in a seemingly well-camouflaged tropical shore crab is a result of active background choice. Taking advantage of a coastal area in the Solomon Islands with variable sand color and a population of the pallid ghost crab Ocypode pallidula with varying carapace color, we experimentally tested whether individuals actively choose specific substrate that best matches their color patterns. We found that individuals taken from extreme sand colors chose substrate that maintained crypsis, with relatively darker crabs typically choosing dark sand and lighter crabs choosing light sand. Crabs of intermediate color pattern, in contrast, showed no clear preference for dark or light sand. Our results suggest that potential prey can actively choose specific backgrounds to enhance and maintain crypsis, providing insights into how behavior interacts with morphological traits to avoid predator detection.

动物拥有多种躲避天敌的策略，其中最为高效的途径之一便是从初始阶段便避免被天敌侦测。学界对与视觉背景相匹配以规避侦测的体色模式演化机制已有较为充分的研究（即隐蔽拟态（crypsis）），但对与这类形态特征协同演化、用以强化或维持隐蔽拟态的具体行为，我们的认知却相对匮乏。本研究旨在探究：在一种伪装效果看似优异的热带滨蟹种群中，其体色与栖息背景的匹配度是否源于主动选择栖息底质。我们依托所罗门群岛一处沙色分布不均的沿海区域，以及壳色存在个体差异的苍白幽灵蟹（Ocypode pallidula）种群开展实验，检验该蟹类个体是否会主动选择最契合自身体色模式的底质。实验结果显示，取自极端沙色环境的蟹类个体均会选择能够维持自身隐蔽拟态的底质：体色相对更深的个体通常偏好深色沙床，体色较浅的个体则倾向选择浅色沙床。与之形成鲜明对比的是，体色处于中间梯度的蟹类个体对深色或浅色沙床均无明显偏好。本研究结果表明，潜在猎物可通过主动选择特定栖息背景来增强并维持隐蔽拟态，这为解析行为与形态特征如何协同作用以规避天敌侦测提供了重要的理论视角。