Meeting Abstract
94.2 Wednesday, Jan. 7 Vacancy chains in different social contexts determine resource acquisition by Coenobita clypeatus terrestrial hermit crabs ROTJAN, Randi*; CHABOT, Jeffrey R; LEWIS, Sara; Harvard University / New England Aquarium; Pfizer, Inc.; Tufts University rrotjan@neaq.org
Hermit crabs require gastropod shell resources for protection. Because shells are often scarce, crabs have evolved complex behavioral and social protocols for shell acquisition via competition. Previous studies on hermit crab resource assessment and competition behaviors have mainly been restricted to simplified laboratory conditions. In contrast, field observations show that shell acquisition in natural populations often involves complex behavioral interactions among conspecifics. Combining lab and field manipulations, we describe vacancy chains, where a single vacant shell initiates a sequential chain of shell switches involving many crabs. Vacancy chain theory has been developed by economists to describe distributions of discrete, reusable resources such as jobs or houses. We tested the central prediction that vacancy chains will provide aggregate benefits distributed across many users when a single new resource becomes available. Lab experiments demonstrated that vacancy chain participants gained significant shell quality improvements. We also experimentally examined how shell damage and crowding, two key dimensions of resource quality, affected the likelihood of winning contests. We introduce a novel resource-use paradigm to accommodate social context, and field observations confirmed 3 social contexts for vacancy chains (asocial, synchronous, and asynchronous), distinguished by differences in shell assessment behaviors and the reversibility of shell switches. Finally, we present an agent-based simulation model to examine how population size and density impact the frequency of vacancy chain types, and the associated behavioral and ecological costs and benefits. Vacancy chain theory represents an innovative approach to understanding resource acquisition behaviors that is applicable across a wide taxonomic range.
