Evolutionary science shows that small, isolated populations are most at risk of extinction. In the Anthropocene, these are increasing. However, some small populations do persist. The Gulf Islands of British Columbia, Canada, were isolated by a rise in sea level several thousand years ago and provide an ideal ecosystem to study naturally occurring small populations isolated over long time periods. Populations of North American Deermouse, Peromyscus maniculatus, inhabit several of these islands and are unlikely to travel between islands, creating well-isolated populations. Through analysis of island populations’ genetic structure, our research aims to determine the evolutionary relationship of different deermouse populations among the Gulf Islands, as well as create a rough divergence timeline. My image shows how we obtain saliva samples that allow for the DNA extraction and genomic analysis of these nocturnal rodents. Understanding the phylogenetic relationship and divergence timeline of these populations will provide insight into the evolution of small populations and how some have persisted through time.