ABSTRACT
To get camouflage successful, an animal and camouflage as a body-part need to be integrated into the environment. When an individual grows, the camouflage is usually modified to maintain integrity. How does the animal maintain the whole body-camouflage system as an individual? We studied the cap making behavior of the sponge crab, Lauridromia dehaani that can carry an artificial sponge as a cap. We obtained the behavioral data including repeated samples from the same individual. The multilevel or hierarchical models are often used to deal with the clustered data. However, the evaluation of the appropriateness of the hierarchical model is a challenge in statistical modeling. This is because the hierarchical model is a statistically non-regular model. Here, we apply marginal-level WAIC (Widely Applicable Information Criterion) to assess the appropriateness of the assumption of the hierarchical structure. We found that the hierarchical models remarkably outperformed non-hierarchical ones in decision making of material size and cap making by the crab, although the performance improvements of the models were small for cap hole making. Our analyses revealed that not only large individuals tend to choose and shape large caps, but also the individual-specific bias emerges in the behavior.
Footnotes
minor revision