Animals avoid predator attack in different ways; some carry defensive structures to reduce predation, with the classic example being hermit crabs and their use of a mollusc shell as a portable refugium. During shell selection, various shell characteristics are investigated by the crab to determine their suitability. Here we consider the role of visual cues. Previous research suggests that some hermit crabs are more likely to initially choose a conspicuous shell but also to move to backgrounds against which they are less conspicuous, suggesting a short-term/long-term trade-off. Across experiments in which we manipulated shell and background colour, we show initially that Pagurus bernhardus prefer black shells over white but this preference was lost in the absence of visual cues. We then show that the strength of preference was dependent on background colour. We repeated this last experiment with red and yellow shells against red or yellow backgrounds to investigate whether this preference extended to chromatic hues. A preference for darker (red) shells was expressed, but preference alteration with background was not observed. P. bernhardus therefore discriminate between shells in terms of shell and background colour, and discrimination may be rooted in a preference for darker shaded shells.

动物以不同的方式避免捕食者的攻击；有些带有防御性结构以减少捕食，最典型的例子是寄居蟹及其将软体动物壳用作便携式避难所。在选择贝壳时，螃蟹会调查各种贝壳的特性，以确定它们的适用性。在这里，我们考虑视觉提示的作用。先前的研究表明，某些寄居蟹更可能最初选择显眼的贝壳，但也会移至其不显眼的背景，这表明了短期/长期的权衡。在操纵外壳和背景色的整个实验中，我们最初显示了Pagurus bernhardus相比于白色，黑壳更喜欢黑壳，但是这种偏好在没有视觉提示的情况下就消失了。然后，我们证明了偏好的强度取决于背景色。我们对红色或黄色背景下的红色和黄色外壳重复了最后一个实验，以研究这种偏好是否扩展到彩色色调。表达了对深色（红色）壳的偏爱，但未观察到背景的偏爱改变。P。因此，bernhardus在外壳和背景颜色方面区分了外壳，而歧视可能源于对深色阴影外壳的偏爱。