Data from: Hiding behavior in Christmas tree worms on different time scales

Many animals escape predators by hiding. Hiding decisions are economic in that individuals trade off the physiological costs of hiding with the benefits of increased security. The number of conspecifics may increase competition, security, or attract predators, influencing predation risk. We studied hiding time in Christmas tree worms (Spirobranchus giganteus), sessile marine invertebrates, which lived with 0–17 other worms within 20cm. Competition and predation risk reduction both predict a shorter latency to re-emerge given the necessity to feed and potential for safety in numbers, respectively. In contrast, if grouped worms attract more predators, individuals should hide longer. We experimentally induced hiding in 174 worms and found a significant, positive relationship between hiding time and number of conspecifics. We repeated the test 4 consecutive times in 1 day on a subset of 30 worms that were either solitary or lived with one other untested worm. We found that worms with longer hiding times habituated more quickly than worms with shorter hiding times, and that the individual worm explained 55.8% of the variation in hiding time. When we conducted the trials for 4 days, we found that the individual worm explained 41.75% of the variation, but no evidence of behavioral plasticity. Worm antipredator responses were consistently individualistic, but behavioral plasticity was only evident over short time scales. For sessile marine invertebrates, higher densities may attract predators, enhancing rather than diluting predation risk. Worms that cannot move away from their neighbors, thus seemingly modify antipredator behavior in consistent ways.诸多动物会通过藏匿行为躲避捕食者。藏匿决策具有经济属性：个体需要在藏匿带来的生理代价与安全感提升带来的收益之间进行权衡。同种个体的数量可能会加剧竞争、提升安全性，或是吸引捕食者，进而影响捕食风险。本研究以圣诞树蠕虫（Spirobranchus giganteus）——一种固着生活的海洋无脊椎动物——为研究对象，这些蠕虫在20厘米范围内可与0至17只其他同种蠕虫共处。考虑到进食的必要性以及群体带来的安全潜力，竞争与捕食风险降低这两个因素，分别会预测出更短的重新出现延迟时长。与之相反，如果群居的蠕虫会吸引更多捕食者，那么个体的藏匿时长应当更长。我们通过实验诱导174只蠕虫进入藏匿状态，结果发现藏匿时长与同种个体数量之间存在显著的正相关关系。我们在1天内对30只蠕虫（要么单独生活，要么与另一只未参与测试的蠕虫共处）连续重复了4次测试，研究发现，藏匿时长更长的蠕虫比藏匿时长更短的蠕虫更快产生习惯化效应，且个体蠕虫因素可以解释55.8%的藏匿时长变异。当我们将测试延续至4天时，发现个体蠕虫因素仍可解释41.75%的变异，但未发现行为可塑性的相关证据。蠕虫的反捕食反应始终具有个体特异性，但行为可塑性仅在短时间尺度下才会显现。对于固着生活的海洋无脊椎动物而言，更高的种群密度可能会吸引捕食者，从而增强而非缓解捕食风险。由于无法远离同类，这类蠕虫似乎会以稳定的方式调整其反捕食行为。