The book "Species speciation in the vole, Microtus montanus, in Wyoming and Colorado" by Sidney Anderson is the result of research devoted to the study of the mechanisms of subspecific speciation in rodents. The author examines in detail the features of evolutionary changes in vole populations in the regions of Wyoming and Colorado, analyzing genetic, size, territorial and behavioral differences between subspecies of Microtus montanus. The book contains unique data and research results that help to better understand the processes of speciation in natural conditions, as well as the importance of preserving biological diversity. For specialists in the field of zoology, evolutionary biology, and environmental protection, this book will be a valuable source of information.