Ecological half-life of caesium in roe deer (Capreolus capreolus)

Biological half-lives for various radionuclides have been determined for many animals kept in the laboratory or under controlled conditions. Only occasionally has been it possible to determine the ecological half-lives of radionuclides in wild animals, where the contamination has occurred in their natural habitats. Following the fallout from the Chernobyl accident and its subsequent ingestion by wildlife, no one knew how long it would take the wild animals to eliminate the radionuclides, and in particular radiocaesium, from their bodies. In this study of roe deer (Capreolus capreolus), bucks (males)were shot at weekly/fortnightly intervals from mid-May till the end of July, as part of the annual cull on an area, which included some young forestry (Stone Chest-National Grid Reference NY48090), planted in 1971/72. The ration of 137Cs:134Cs, typical of the Chernobyl fallout, was seldom observed in these animals due to the highly variable concentrations of 137Cs originating from bomb fallout. Therefore, 134Cs was used instead because its presence was almost entirely due to the Chernobyl fallout. After using log10 transformation of the 134Cs concentrations, a significant (p < 0.01) regression was obtained which accounted for 85% of the variation. From the regression, the ecological half-life for 134Cs was found to be 28.3 days.