Does social behavior drive vole cycles? An evaluation of competing models as they pertain to California voles

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The literature contains a number of verbal and mathematical models that assert that social behavior drives the multiannual density cycles characteristic of many vole species. Many of the assumptions about vole behavior on which the models are based remain unverified. In this paper we briefly review these models and their underlying assumptions. We then use natural history data on the social behavior of California voles (Microtus californicus) to critically examine the plausibility of these assumptions. We do not attempt to explain vole cycles, but only to evaluate models that rely strongly on social behavior as a critical component. Our results indicate that (i) critical assumptions of the behavioral polymorphism, social stress, and social breakdown hypotheses are not met; (ii) some assumptions of the kin selection hypothesis are met whereas others are not; and (iii) assumptions of the habitat patchiness – dispersal hypothesis are met. However, published models of dispersal and habitat patchiness must invoke additional factors, such as resource depletion or predation, before cycles result. We conclude that social behavior is unlikely to be a driving force in the generation of cycles in the California vole. We hope that our approach will stimulate further research specifically directed at assumptions of these models.