Radioactive wild boars have roamed the forests of Germany for decades. Scientists believed their radioactivity is from the 1986 Chernobyl nuclear disaster. However, other animals are not as radioactive. Levels of radioactive caesium decreased over the years in other creatures. This has puzzled scientists because radioactivity in wild boars is at high levels. Scientists dubbed this mystery the "wild boar paradox". Research says the contamination of the wild boars is from nuclear weapons tests last century. The Chernobyl caesium has a much shorter life than that in nuclear weapons.

Scientists believe wild boars have remained so radioactive because of their love of truffle mushrooms. Radioactive particles accumulate in these underground fungi, which the boars eat. The levels of caesium in boars make the animals too dangerous to be eaten. This has led to a reduction in the hunting of the animals and a proliferation of their numbers. A geochemist asked why the effects of nuclear weapons testing on the environment has been "under-studied and largely forgotten". He said caesium soil pollution will "haunt generations to come".