Reproductive potential in a wild boar population exposed for multiple generations to chronic low-dose radiation in Fukushima, Japan.

Releases of anthropogenic radionuclides can cause acute and long-term effects to organisms, reducing survival and recruitment and potentially leading to population-level and ecosystem-wide consequences. Acute radiotoxicity is known to induce oxidative stress, DNA damage, immunosuppression, and reproductive failure. Human biomedical studies of acute radiation exposure have demonstrated severe reproductive consequences including ovarian toxicity, sterilization, and premature reproductive senescence. Yet, little is known about the reproductive effects of chronic exposure to low-dose rates of ionizing radiation in humans or wild mammals. Here, we present the most comprehensive assessment to date of reproductive health in a free-ranging large mammal inhabiting a landscape with widespread radiation contamination. We evaluated the reproductive consequences of multigenerational, chronic low-dose radiation exposure within the Fukushima Difficult-to-Return-to-Zone (DRZ), which received the highest fallout from the 2011 nuclear accident. We hypothesized that female wild boar with higher radiation exposure would exhibit reduced lifetime reproductive potential compared to boar exposed to less contamination. Specifically, we predicted that individuals exposed to higher dose rates would have fewer ovarian follicles and lower concentrations of reproductive hormones. We found no evidence that low dose environmental radiation negatively affected follicle abundance or hormone concentrations. Thus, despite chronic, low-dose exposure to radiation experienced by wild boar within the DRZ, these exposures appear to be insufficient to result in diminished reproductive function or capacity and are unlikely to trigger cascading impacts to population dynamics.