Purpose: The assessment of biological consequences of long-term low dose-rate radiation on wild animals after Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident is important. Many studies on wild animals have showed both negligible and significant effects on various species, but our study is the first to assess effects on hematopoietic progenitor cells (HPCs) in large Japanese field mice (Apodemus speciosus).Materials and methods: In April 2015, A. speciosus were collected from three contaminated sites in Namie Town. Mice from a non-contaminated control area-Hirosaki-were collected in May 2015. The air dose-rates 1m above the ground and dose-rates from soil at the control and contaminated areas were 0.96 ± 0.05 μGy/d (air, Hirosaki), 1.01 ± 0.05 μGy/d (soil, Hirosaki), 14.4 ± 2.4 μGy/d (air, Tanashio), 15.5 ± 4.4 μGy/d (soil, Tanashio), 208.8 ± 31.2 μGy/d (air, Ide), 211.7 ± 41.3 μGy/d (soil, Ide), 470.4 ± 93.6 μGy/d μGy/d (air, Omaru), 471.2 ± 192.9 μGy/d (soil, Omaru) respectively. We investigated possible DNA damage and pro-inflammatory markers in the interphase nuclei of A. speciosus bone marrow cells. Colony forming potential of bone marrow cells were estimated by the number of HPC colony-forming cells (CFU-GM, BFU-E, and CFU-Meg). Radiation induced genomic instability (RIGI) in HPCs was also analyzed by quantifying delayed DNA damage induction in CFU-GM clones.Results: Although no significant differences in DNA damage and inflammation markers were observed in A. speciosus bone marrow cells from control and contaminated areas, the number of HPC colonies (CFU-GM, BFU-E, and CFU-Meg) exhibited an inverse correlation with air dose-rate. With regards to RIGI, we observed no significant differences in DNA damage of CFU-GM clones between the mice from the control and the three contaminated areas.Conclusions: Our study suggests that low dose-rate radiation of more than 200 μGy/d reduced HPCs in A. speciosus, possibly eliminating genomically unstable HPCs.