The vacancy chain process: a new mechanism of resource distribution in animals with application to hermit crabs

Abstract

A number of resources important to humans such as jobs in bureaucracies, houses and apartments are allocated through a mechanism known as a vacancy chain. In a vacancy chain process an initial, vacant resource unit entering a population of users is taken by a first individual who leaves his/her previous resource unit behind, which is taken by a second individual, and so on. In this process an initial resource unit works both directly and indirectly to provide opportunities for several individuals to gain new and better resources. Vacancy chains are hypothesized to be important in resource distribution for a variety of non-human animals, and it is documented, in particular, that the hermit crab Pagurus longicarpus gets the gastropod shells in which it lives through this mechanism. The direct and indirect effects of vacancy chains on hermit crabs and the systematic ways in which chains flow through groups of crabs and their resources are indicated. In systems where they occur, it is further hypothesized that vacancy chains have unique implications for the ecology of resource users. Several of these hypotheses are explored using the example of hermit crabs.