Bluefish Caves 1, 2, and 3 have produced tens of thousands of vertebrate remains among which at least nine species of microtine rodents are represented: red-backed vole, Clethrionomys rutilus; collared lemming, Dicrostonyx torquatus; brown lemming, Lemmus sibiricus; singing vole, Microtus miurus; tundra vole, Microtus oeconomus; meadow vole, Microtus pennsylvanicus; yellow-cheeked or taiga vole, Microtus xanthognathus; muskrat, Ondatra zibethicus; and northern bog lemming, Synaptomys borealis. Late Pleistocene and Holocene components are clearly distinguishable from one another in each of the three caves, and each component can be subdivided within cave 1. This paper discusses (i) variations in taxonomic abundance through time and between site areas, (ii) contrasts in microhabitat between north-facing cave 1 and south-facing cave 2, and (iii) decreases in tooth size that may reflect a reduction in the length of the growing season. A general decrease in diversity is shown to involve increased dominance and decreased species richness and evenness. These changes are attributed to postglacial zonation of habitat.