Found only on Muskeget Island, the Beach Vole became isolated from its closest relative, the Meadow Vole, about 3,000 years ago during a glacial melt and rise in sea level. It is the only mammal endemic to Massachusetts, the result of genetic isolation from the mainland Meadow Vole. Learn more about the Microtus breweri, more commonly known as a Beach Vole, in this easy-to-read species overview by the Smithsonian's National Museum of Natural History.