The purpose of this study was to use Microtus guentheri to monitor gamma radioactivity levels in the Mersin region of southern Mediterranean Turkey, where the nation's first nuclear power plant will be built. Prior to our study there was no information available on the radioactivity levels of living organisms in this region. Concentrations of 226Ra, 232Th, 40K, and 137Cs were determined by gamma spectrometry using a high-purity germanium detector and our results were compared with the associated dose rates in the world. The average value of gamma dose rates obtained in this study (7.59 nGy h-1) was in the range of 3.61-20.12 nGy h-1, which is within the global range of values for soil (10-200 nGy h-1). The calculated annual effective dose equivalent with an average value of 9.30 mSv and the radium equivalent activity index with an average value of 15.13 Bq/kg were lower than the worldwide averages for soil of 460 mSv and 370 Bq/kg, respectively. The annual gonadal equivalent dose and excess lifetime cancer risk averaged 386.74 µS/y and 0.93, respectively. There was a strong positive correlation between increasing altitude and 40K activity (r = 0.996, P < 0.0001). The data presented in this study are baseline data that will be useful in monitoring for fugitive radiation associated with the nuclear power plant planned for the Mersin region.