In Chernobyl, Mammals Tread Lightly Through Radiation Zones

Twenty-six years after the disaster, not all species have been impacted the same. Wolves, for example, seem to be unaffected.
A wolf print in Chernobyl snow, circa 2009. (Photo: Courtesy T.A. Mousseau)
Dec 10, 2012· 2 MIN READ
Rachel is a science journalist writing for venues such as The New York Times and Smithsonian.

Getting coated in radiation is never good news, regardless of whether you’re a human, bird or insect. On April 26, 1986, Chernobyl dumped radioactive material hundreds of times the amount contained in the nuclear bombs in Hiroshima and Nagasaki into the surrounding forests and fields.

Overall and not surprisingly, animals declined as the lingering radiation in the environment increased. There was one exception, however—wolves.

While some residents anecdotally reported spikes in wildlife as time passed, rigorous scientific studies were lacking. How the local flora fared following the disaster—even 26 years later—remained a mystery.

“In the early years following the disaster, it was actually very, very difficult for scientists to do this kind of work,” said Timothy Mousseau, a biologist at the University of South Carolina at Columbia. “Studies were very much discouraged, and some scientists from Belarus were actually exiled,” he said.

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Following the fall of the Soviet Union, few resources existed for undertaking basic ecological studies around Chernobyl. In the early 2000s, however, Mousseau and his colleagues managed to secure funding and permits to undertake some of the first animal impact surveys in the area.

Mousseau and his team started with birds, and then moved on to insects, spiders and small rodents. Now, he and co-author Andres Moller have completed the first known large mammal census, publishing their results in the journal Ecological Indicators.

To tackle the mammal question, Mousseau and Moller counted animal tracks in fresh snow along 161 100-meter long transects representing an array of different habitats and radiation levels around Chernobyl. They found 445 different tracks belonging to 12 different mammal species. They encountered red fox tracks most often, followed by wolves and hares.

Overall and not surprisingly, animals declined as the lingering radiation in the environment increased. There was one exception, however. Wolves showed no reaction to background radiation, being just as likely to wander into highly contaminated zones as safer ones. Though the researchers don’t know for sure, Mousseau hypothesizes that wolves may be drawn to weakened prey in the contamination zones. A surplus of sick, easy-to-catch rabbits, for example, may lure the hungry predators in and cause their population to boom, at least on the short term.

Another explanation may be that wolves simply have very large territory sizes and that the scale of this experiment may not have been suitable for quantifying their entire range. “The wolves may not show a pattern just because there’s a mismatch in the scale of their territory versus the scale of contamination,” Mousseau said. Either way, wolves seem to be increasing disproportionately with the number of prey in areas with high levels of radiation, while other mammals seem to be avoiding radiation zones altogether.

Whether or not these results will apply to additional contaminated sites, like Fukushima, remains to be seen. Chernobyl occurred over two decades ago, while Fukushima is only approaching its second anniversary. But even in Japan, Mousseau said, research dollars and incentive to investigate these questions lag behind efforts to study the radiation’s effects on humans, though Mousseau and his group hope to secure support to follow multiple generations of animals in Fukushima. This way, they could see if mutations and impacts accumulate over time. He suspects, however, that they will.

The researchers still don’t understand why some species like wolves may respond differently to radiation’s mutation-inducing effects compared to others. “This is really just the first sort of snapshot of what’s going on,” Mousseau said. “The next question is why some individuals are not affected at all by the radiation and others are basically killed by it.”

He and his team hope to perform larger studies, including sampling individual animals in Chernobyl for genetic material and longevity, in order to tease out the ways that radiation’s impacts cascade from genes to individuals to populations and, ultimately, to the entire ecological community.

“Not all species are impacted to the same degree, but the main message is that every major component of the biological community and ecosystem have been impacted by these radioactive elements,” Mousseau said. “Now we have the mammal component of this system, and, of course, human’s being mammals, this is of particular relevance to human populations living in the area as well.”

Rachel Nuwer is a science journalist writing for venues such as The New York Times, Scientific American, Smithsonian and Audubon Magazine, among others. She lives in Brooklyn. | @rachelnuwer |