Alternative camouXage strategies mediate predation risk among closely related co-occurring kelp crabs

Although camouXage is a common predator defense strategy across a wide variety of organisms, direct tests of the adaptive and ecological consequences of camouXage are rare. In this study, we demonstrated that closely related crabs in the family Epialtidae coexist in the same algal environment but use alternative forms of camouXage– –decoration and color change––to protect themselves from predation. Decoration and color change are both plastic camouXage strategies in that they can be changed to match diVerent habitats: decoration occurs on a short timescale (hours to days), while color change accompanies molting and occurs on longer timescales (months). We found that the species that decorated the most had the lowest magnitude of color change (Pugettia richii); the species that decorated the least showed the highest magnitude of color change (Pugettia producta), and a third species (Mimulus foliatus) was intermediate in both decoration and color change, suggesting a negative correlation in utilization of these strategies. This negative correlation between color change and decoration camouXage utilization mirrored the eVectiveness of these camouXage strategies in reducing predation in diVerent species. Color camouXage primarily reduced predation on P. producta, while decoration camouXage (but not color camouXage) reduced predation on P. richii. These results indicate there might be among-species trade-oVs in utilization and/or eVectiveness of these two forms of plastic camouXage, with important consequences for distribution of these species among habitats and the evolution of diVerent camouXage strategies in this group.