Radioactive wild boars have been roaming the forests of Germany for decades. Scientists believed their radioactivity was due to the 1986 Chernobyl nuclear disaster. However, the animals' radioactivity has long mystified scientists because while levels of radioactive caesium in other animals has decreased over the years, radioactivity in wild boars has persisted at high levels. Scientists have dubbed this mystery the "wild boar paradox". New research now attributes the contamination of Germany's wild boars to nuclear weapons tests from the mid-20th century. The Chernobyl reactor produced caesium-137, which has a much shorter life than the caesium-135 created by nuclear weapons.

Scientists believe the reason wild boars have remained so radioactive compared to other forest creatures is their love of the delicacy truffle mushrooms. Radioactive particles accumulate in these underground fungi, which form part of the boars' diet. The high levels of caesium in boars make the animals too dangerous to be eaten under German law. This has resulted in a reduction in the hunting of the animals, which has led to a proliferation of their numbers. Geochemist James Kaste asks why the effects of nuclear weapons testing on the environment have been "under-studied and largely forgotten". He said: "This is one of the ultimate case studies showing how legacy soil pollution can haunt generations to come."