The prevalence of macroscopic bone anomalies in the appendicular skeleton of wild rodents and, particularly, fossorial species is not well known. We examined 8,257 bones corresponding to 564 collection specimens (249 males and 315 females) of a fossorial form of water vole (Arvicola terrestris monticola). Animals were obtained monthly from July 1983 to December 1984 in the Aran Valley (Pyrenees). Most macroscopic anomalies were healed fractures or exostoses. The prevalence of anomalies was not significantly different between males and females but was clearly higher in adults than in juveniles and subadults. The frequency of alterations in the thoracic limb long bones was significantly higher than that in the pelvic counterparts. Aggressive intraspecific interactions and biomechanical factors related to burrowing may be associated with these differences. In females, remodeling of the innominate shape because of pregnancy and parturition could enhance fractures and exostoses in this structure.