The environmental factors that arrest breeding in prairie voles during the middle of the breeding season are unknown. The role of water availability on reproductive function was examined by limiting water intake to 50% of ad lib water consumption for 10 weeks. At autopsy, testicular, epididymal and seminal vesicle masses were reduced in water restricted males as compared to animals with ad lib access to water. Body mass was also reduced in water restricted males. Plasma testosterone levels and the number of testicular and epididymal sperm were significantly reduced in water restricted voles as compared to animals drinking water ad lib, but plasma levels of luteinizing hormone were unaffected. Taken together, these data suggest that reduced water availability can inhibit male prairie vole breeding.