hreatened or endangered. Muskrat populations have been reduced in some streams where North American river otters (Lontra canadensis) were reintroduced, and it has been hypothesized that otter reintroduction could be used as a tool for conservation of mussels. We used occupancy estimation methods to evaluate the ecological relationship between muskrats and otters by collecting presence–absence data based on field sign found at bridge crossings in eastern and central Kentucky. Mean detection probabilities (ps) and occupancy probabilities (ψs) for muskrats were 0.692 (SE = 0.045) and 0.723 (SE = 0.071) and for otters were 0.623 (SE = 0.036) and 0.662 (SE = 0.069), respectively. Otter occupancy was related negatively to distance from release sites, which suggests that the otter population is still expanding its range. A 2-species interaction model indicated that the occupancy by muskrats and river otters was independent, and we conclude that river otter reintroduction would not be an effective strategy for conserving mussels.