Competition and Coexistence of Mobile Animals

Abstract

Competitive interactions among species lie at the foundation of our understanding of the structure and diversity of ecological communities. For the past century, various theoretical, laboratory and field studies have sought to understand how species that compete can coexist. Almost two decades ago, two influential reviews (Connell 1983; Schoener 1983) demonstrated that, at least in published studies, interspecific competition appears to be frequent. Just as importantly, these reviews found little evidence for competitive exclusion, that is, when one species completely eliminates another species when they occur together. In these reviews, competitive exclusion appeared especially rare for mobile animal species, as opposed to sedentary species such as inter-tidal organisms and vascular plants. Since 1983, competition theory has focused on identifying mechanisms to explain this “unexpected” prevalence of coexistence. In this chapter, I show that mobile animal species are highly likely to coexist because of their ability to move and make choices. These choices result in resource or habitat partitioning that allow exclusive use of resources, so that the structure of communities can be predicted largely in the absence of detailed knowledge of competitive dynamics.