BERKE, Sarah K; WOODIN, Sarah A; Univ of South Carolina; Univ of South Carolina: Behavioral balancing acts: energy and mortality trade-offs in young decorator crabs

To address the fitness impacts associated with a common behavior (decoration of the body surface), we conducted experiments assessing the impact of decorating behavior on growth and mortality risk in young decorator crabs, Oregonia gracilis. Young crabs live hidden within colonies of bryozoans and hydroids, zoids of which are attached to the carapace and legs as decoration, which can weigh as much as the crab itself. To determine whether the decoration poses an energetic burden, we measured weight loss under conditions of starvation for decorated and undecorated crabs. We demonstrated that starved young crabs loose weight more quickly when carrying decoration, suggesting that this behavior is energetically costly. To determine whether decoration also provides camouflage against predators, we conducted a tethering experiment comparing predation risk in decorated versus undecorated crabs, raising the possibility that energetic costs are offset by mortality benefits to create a net fitness benefit. Behavioral ecologists have long been aware that such trade-offs exist, but describing them quantitatively can be difficult because energy and mortality are measured in different units. Approaches for determining the fitness �equivalence� of energy and mortality components will be discussed.