The ability of species to migrate and disperse is a trait that has interested ecologists for many years. Now that many species and ecosystems face major environmental threats in the shape of habitat fragmentation and global climate change, the ability of species to adapt to these changes by dispersing, migrating, or moving between different patches of habitat can be crucial to ensuring their survival. This text provides an overview of the study of dispersal. The causes, mechanisms, and consequences of dispersal at the individual, population, and species levels are considered. The promise of new techniques and models for studying dispersal, drawn from molecular biology and from demography, is explored. Perspectives on the study of dispersal are offered from evolution, conservation biology, and genetics. Throughout the book, theoretical approaches are combined with empirical data, and care has been taken to include examples from as wide a range of species as possible.