Bisons stand in the forest of the state radiation ecology reserve in the 30 km (18 miles) exclusion zone around the Chernobyl nuclear reactor near the village of Babchin, some 370 km (217 miles) southeast of Minsk, February 21, 2011. Belarus, Ukraine and Russia will mark the 25th anniversary of the nuclear reactor explosion in Chernobyl, the place where the world's worst civil nuclear accident took place, on April 26. REUTERS/Vasily Fedosenko (BELARUS - Tags: ANNIVERSARY DISASTER ANIMALS)