Mercury concentrations in dead red-crowned cranes in southeastern Hokkaido have been found to be 10 times higher on average and as much as 300 times the maximum generally found in birds, researchers said Monday.
It is the first time a high concentration of mercury has been found in the large "tancho" white-feathered cranes, which have been designated a special national natural treasure.
Hiroki Teraoka, a professor of veterinary toxicology at Rakuno Gakuen University who led the study, said one crane probably died of mercury poisoning because the level of the toxin in its system was 300 times greater than normal.