For diurnal animals that heavily rely on vision, a nocturnal resting strategy that offers protection when vision is compromised, is crucial. We found a population of a common European jumping spider (Evarcha arcuata) that rests at night by suspending themselves from a single silk thread attached overhead to the vegetation, a strategy categorically unlike typical retreat-based resting in this group. In a comprehensive study, we collected the first quantitative field and qualitative observation data of this surprising behaviour and provide a detailed description. We tested aspects of site fidelity and disturbance response in the field to assess potential functions of suspended resting. Spiders of both sexes and all developmental stages engage in this nocturnal resting strategy. Interestingly, individual spiders are equally able to build typical silk retreats and thus actively choose between different strategies inviting questions about what factors underlie this behavioural choice. Our preliminary data hint at a potential sensory switch from visual sensing during the day to silk-borne vibration sensing at night when vision is compromised. The described behaviour potentially is an effective anti-predator strategy either by acting as an early alarm system via vibration sensing or by bringing the animal out of reach for nocturnal predators. We propose tractable hypotheses to test an adaptive function of suspended resting. Further studies will shed light on the sensory challenges that animals face during resting phases and should target the mechanisms and strategies by which such challenges are overcome.

中文翻译：

---

挂线：跳跃的蜘蛛具有异常的夜间休息行为

对于严重依赖视力的昼夜动物，夜间休息策略可在视力受到损害时提供保护，这一点至关重要。我们发现了一群普通的欧洲跳跃蜘蛛（Evarcha arcuata），它们通过将自身从附着在植被上方的单条丝线悬吊下来，在夜间休息，这一策略与该组典型的基于静养的休息方式完全不同。在全面的研究中，我们收集了这种令人惊讶的行为的第一个定量场和定性观察数据，并提供了详细的描述。我们在现场测试了站点保真度和干扰响应的方面，以评估悬浮休息的潜在功能。雌雄同体的蜘蛛和所有发育阶段的蜘蛛都参与这种夜间休息策略。有趣的是，个体蜘蛛同样有能力建造典型的丝绸撤退点，因此可以在不同的策略之间积极选择，从而引发有关此行为选择背后的因素的疑问。我们的初步数据表明，当视力受到损害时，可能会从白天的视觉感知转换为晚上的丝绸传播的振动感知。所描述的行为可能是有效的反捕食者策略，它既可以通过振动感应充当预警系统，也可以使动物无法进入夜间捕食者的行列。我们提出易处理的假设，以测试悬浮休息的适应性功能。进一步的研究将揭示动物在休息阶段面临的感觉挑战，并应针对克服这些挑战的机制和策略。