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.诸多动物通过藏匿行为躲避捕食者。藏匿决策具有经济学属性：个体需权衡藏匿带来的生理代价与安全感提升所带来的收益。同种个体（conspecifics）的数量可能会加剧种内竞争、提升群体安全感，或是吸引更多捕食者，进而影响捕食风险。本研究以圣诞树蠕虫（Spirobranchus giganteus）——固着型（sessile）海洋无脊椎动物——为对象，其20厘米栖息范围内可共存0至17只同种蠕虫。基于觅食的必要性以及群体安全的潜在效应，种内竞争与捕食风险降低这两个因素，均会预测蠕虫重新探出的潜伏期更短。反之，若集群的蠕虫吸引了更多捕食者，则个体的藏匿时长应当更长。我们通过实验手段诱导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正相关关系。我们针对30只子集个体（这些个体要么单独栖息，要么与另一只未参与测试的蠕虫共同栖息），在1天内连续4次重复开展测试，结果发现：藏匿时长更长的蠕虫比时长更短的蠕虫习惯化（habituation）速度更快，且个体差异可解释55.8%的藏匿时长变异。当我们将测试周期延长至4天时，个体差异仍可解释41.75%的变异，但未发现行为可塑性（behavioral plasticity）的相关证据。蠕虫的反捕食响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。对于固着型海洋无脊椎动物而言，更高的种群密度可能会吸引更多捕食者，从而加剧而非稀释捕食风险。由于无法主动远离同类，这类蠕虫似乎会以稳定的方式调整其反捕食行为。