Wild boars of Bavaria, Germany

Weapons tests also spread contamination by shooting thick swells of radiated dust and ash called fallout into the upper atmosphere, where it can circle the planet and settle in distant environments.

In the forests of Bavaria, for example, some wild boars occasionally hold staggering levels of radiation. Scientists long assumed that fallout was produced by the catastrophic 1986 meltdown of the Chernobyl Nuclear Power Plant in nearby Ukraine.

In a recent study, however, Steinhauser and his team found that up to 68 percent of contamination in Bavarian boars came from global nuclear testing—conducted anywhere from Siberia to the Pacific. By finding the “nuclear forensic fingerprint” of different isotopes of cesium, some of which are radioactive, Steinhauser’s team ruled out Chernobyl as the source of contamination.

The boars became contaminated through eating truffles, which absorbed radiation from nuclear fallout that settled into the nearby ground.

Steinhauser studied samples of wild boars, usually from their tongues, finding 15,000 becquerels of radiation for every kilogram of meat. These numbers far exceeded the European safety limit of 600 becquerels per kilogram.

When the first results came back, one of Steinhauser’s PhD students said: “These must be wrong … It’s not possible that there’s this much weapons cesium in the wild boars,” he recalls. It was only after they checked the measurements again that they concluded that the “boars are carrying way more old nuclear weapons fallout cesium than they were supposed to be.”

Tongue samples from wild boars in Bavaria have shown as much as 15,000 becquerels of radiation per kilogram.

Reindeer of Norway

Reindeer in Norway showed evidence of nuclear signatures after eating mushroom and lichen affected by radiation from Chernobyl.

Macacques of Japan

In Japan, a similar problem plagues red-faced monkeys.

After the catastrophic meltdown of the country’s Fukushima Daiichi Nuclear Power Plant in 2011, the concentration of cesium in nearby Japanese macaques rocketed upwards to a maximum of 13,500 becquerels per kilogram, according to a study led by Shin-ichi Hayama, a professor at Nippon Veterinary and Life Science University.

According to Hayama’s research, which mainly focused on tissue samples from the macaques’ hind legs, they likely absorbed the contamination by eating buds and bark on local trees, as well as other foods like mushrooms and bamboo shoots, all of which take in radioactive cesium from the ground.

The high concentrations of cesium, which have declined over the last decade, led Hayama to speculate that monkeys born after the accident may have experienced delayed growth and had smaller heads.