The bright, the bold and the toxic: do coloration, personality, and toxicity represent an integrated phenotype in fire salamanders?

Defensive coloration such as bright colors used to advertise secondary defenses (i.e., aposematic coloration) is very common but also shows high intraspecific variation. Similarly, consistent among-individual differences in behavior (i.e., animal personality) are pervasive in the animal kingdom. Therefore, aposematism and personality could be linked to produce an optimal defensive phenotype, however, this has not formally been investigated. Here, we used the European fire salamander (Salamandra salamandra) to study if personality traits correlate with an individual’s proportion of yellow and relative toxin gland size using open field tests and observations during husbandry. Four of the five tested behaviors showed low to moderate but significant repeatabilities. However, only the activity during husbandry showed a positive correlation with the relative toxin gland size indicating a potential trade-off between foraging and the costs of chemical defenses. Furthermore, three of the four personality traits showed strong correlations between them, and all personality traits were higher in fire salamanders collected in fall compared to spring, indicating the importance of seasonality effects on fire salamander personality. While we found little evidence for a potential role of trait integration maintaining individual variation in behavior and coloration of fire salamanders, future studies on personality traits in aposematic species should consider the potential of covariation of personality with coloration and/or toxicity.